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Set this flag if the CPU has an IBPB implementation that does not
invalidate return target predictions. Zen generations < 4 do not flush
the RSB when executing an IBPB and this bug flag denotes that.
[ bp: Massage. ]
Signed-off-by: Johannes Wikner <[email protected]>
Signed-off-by: Borislav Petkov (AMD) <[email protected]>
Cc: <[email protected]>
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AMD's initial implementation of IBPB did not clear the return address
predictor. Beginning with Zen4, AMD's IBPB *does* clear the return address
predictor. This behavior is enumerated by CPUID.80000008H:EBX.IBPB_RET[30].
Define X86_FEATURE_AMD_IBPB_RET for use in KVM_GET_SUPPORTED_CPUID,
when determining cross-vendor capabilities.
Suggested-by: Venkatesh Srinivas <[email protected]>
Signed-off-by: Jim Mattson <[email protected]>
Signed-off-by: Borislav Petkov (AMD) <[email protected]>
Reviewed-by: Tom Lendacky <[email protected]>
Reviewed-by: Thomas Gleixner <[email protected]>
Cc: <[email protected]>
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git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm
Pull power management updates from Rafael Wysocki:
"These add a new cpufreq driver for Loongson-3, add support for new
features in the intel_pstate (Lunar Lake and Arrow Lake platforms, OOB
mode for Emerald Rapids, highest performance change interrupt),
amd-pstate (fast CPPC) and sun50i (Allwinner H700 speed bin) cpufreq
drivers, simplify the cpufreq driver interface, simplify the teo
cpuidle governor, adjust the pm-graph utility for a new version of
Python, address issues and clean up code.
Specifics:
- Add Loongson-3 CPUFreq driver support (Huacai Chen)
- Add support for the Arrow Lake and Lunar Lake platforms and the
out-of-band (OOB) mode on Emerald Rapids to the intel_pstate
cpufreq driver, make it support the highest performance change
interrupt and clean it up (Srinivas Pandruvada)
- Switch cpufreq to new Intel CPU model defines (Tony Luck)
- Simplify the cpufreq driver interface by switching the .exit()
driver callback to the void return data type (Lizhe, Viresh Kumar)
- Make cpufreq_boost_enabled() return bool (Dhruva Gole)
- Add fast CPPC support to the amd-pstate cpufreq driver, address
multiple assorted issues in it and clean it up (Perry Yuan, Mario
Limonciello, Dhananjay Ugwekar, Meng Li, Xiaojian Du)
- Add Allwinner H700 speed bin to the sun50i cpufreq driver (Ryan
Walklin)
- Fix memory leaks and of_node_put() usage in the sun50i and
qcom-nvmem cpufreq drivers (Javier Carrasco)
- Clean up the sti and dt-platdev cpufreq drivers (Jeff Johnson,
Raphael Gallais-Pou)
- Fix deferred probe handling in the TI cpufreq driver and wrong
return values of ti_opp_supply_probe(), and add OPP tables for the
AM62Ax and AM62Px SoCs to it (Bryan Brattlof, Primoz Fiser)
- Avoid overflow of target_freq in .fast_switch() in the SCMI cpufreq
driver (Jagadeesh Kona)
- Use dev_err_probe() in every error path in probe in the Mediatek
cpufreq driver (Nícolas Prado)
- Fix kernel-doc param for longhaul_setstate in the longhaul cpufreq
driver (Yang Li)
- Fix system resume handling in the CPPC cpufreq driver (Riwen Lu)
- Improve the teo cpuidle governor and clean up leftover comments
from the menu cpuidle governor (Christian Loehle)
- Clean up a comment typo in the teo cpuidle governor (Atul Kumar
Pant)
- Add missing MODULE_DESCRIPTION() macro to cpuidle haltpoll (Jeff
Johnson)
- Switch the intel_idle driver to new Intel CPU model defines (Tony
Luck)
- Switch the Intel RAPL driver new Intel CPU model defines (Tony
Luck)
- Simplify if condition in the idle_inject driver (Thorsten Blum)
- Fix missing cleanup on error in _opp_attach_genpd() (Viresh Kumar)
- Introduce an OF helper function to inform if required-opps is used
and drop a redundant in-parameter to _set_opp_level() (Ulf Hansson)
- Update pm-graph to v5.12 which includes fixes and major code revamp
for python3.12 (Todd Brandt)
- Address several assorted issues in the cpupower utility (Roman
Storozhenko)"
* tag 'pm-6.11-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm: (77 commits)
cpufreq: sti: fix build warning
cpufreq: mediatek: Use dev_err_probe in every error path in probe
cpufreq: Add Loongson-3 CPUFreq driver support
cpufreq: Make cpufreq_driver->exit() return void
cpufreq/amd-pstate: Fix the scaling_max_freq setting on shared memory CPPC systems
cpufreq/amd-pstate-ut: Convert nominal_freq to khz during comparisons
cpufreq: pcc: Remove empty exit() callback
cpufreq: loongson2: Remove empty exit() callback
cpufreq: nforce2: Remove empty exit() callback
cpupower: fix lib default installation path
cpufreq: docs: Add missing scaling_available_frequencies description
cpuidle: teo: Don't count non-existent intercepts
cpupower: Disable direct build of the 'bench' subproject
cpuidle: teo: Remove recent intercepts metric
Revert: "cpuidle: teo: Introduce util-awareness"
cpufreq: make cpufreq_boost_enabled() return bool
cpufreq: intel_pstate: Support highest performance change interrupt
x86/cpufeatures: Add HWP highest perf change feature flag
Documentation: cpufreq: amd-pstate: update doc for Per CPU boost control method
cpufreq: amd-pstate: Cap the CPPC.max_perf to nominal_perf if CPB is off
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 SEV updates from Borislav Petkov:
- Add support for running the kernel in a SEV-SNP guest, over a Secure
VM Service Module (SVSM).
When running over a SVSM, different services can run at different
protection levels, apart from the guest OS but still within the
secure SNP environment. They can provide services to the guest, like
a vTPM, for example.
This series adds the required facilities to interface with such a
SVSM module.
- The usual fixlets, refactoring and cleanups
[ And as always: "SEV" is AMD's "Secure Encrypted Virtualization".
I can't be the only one who gets all the newer x86 TLA's confused,
can I?
- Linus ]
* tag 'x86_sev_for_v6.11_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
Documentation/ABI/configfs-tsm: Fix an unexpected indentation silly
x86/sev: Do RMP memory coverage check after max_pfn has been set
x86/sev: Move SEV compilation units
virt: sev-guest: Mark driver struct with __refdata to prevent section mismatch
x86/sev: Allow non-VMPL0 execution when an SVSM is present
x86/sev: Extend the config-fs attestation support for an SVSM
x86/sev: Take advantage of configfs visibility support in TSM
fs/configfs: Add a callback to determine attribute visibility
sev-guest: configfs-tsm: Allow the privlevel_floor attribute to be updated
virt: sev-guest: Choose the VMPCK key based on executing VMPL
x86/sev: Provide guest VMPL level to userspace
x86/sev: Provide SVSM discovery support
x86/sev: Use the SVSM to create a vCPU when not in VMPL0
x86/sev: Perform PVALIDATE using the SVSM when not at VMPL0
x86/sev: Use kernel provided SVSM Calling Areas
x86/sev: Check for the presence of an SVSM in the SNP secrets page
x86/irqflags: Provide native versions of the local_irq_save()/restore()
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When CPUID[6].EAX[15] is set to 1, this CPU supports notification for
HWP (Hardware P-states) highest performance change.
Add a feature flag to check if the CPU supports HWP highest performance
change.
Signed-off-by: Srinivas Pandruvada <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Rafael J. Wysocki <[email protected]>
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I'm getting tired of telling people to put a magic "" in the
#define X86_FEATURE /* "" ... */
comment to hide the new feature flag from the user-visible
/proc/cpuinfo.
Flip the logic to make it explicit: an explicit "<name>" in the comment
adds the flag to /proc/cpuinfo and otherwise not, by default.
Add the "<name>" of all the existing flags to keep backwards
compatibility with userspace.
There should be no functional changes resulting from this.
Acked-by: Dave Hansen <[email protected]>
Signed-off-by: Borislav Petkov (AMD) <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
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The SVSM specification documents an alternative method of discovery for
the SVSM using a reserved CPUID bit and a reserved MSR. This is intended
for guest components that do not have access to the secrets page in
order to be able to call the SVSM (e.g. UEFI runtime services).
For the MSR support, a new reserved MSR 0xc001f000 has been defined. A #VC
should be generated when accessing this MSR. The #VC handler is expected
to ignore writes to this MSR and return the physical calling area address
(CAA) on reads of this MSR.
While the CPUID leaf is updated, allowing the creation of a CPU feature,
the code will continue to use the VMPL level as an indication of the
presence of an SVSM. This is because the SVSM can be called well before
the CPU feature is in place and a non-zero VMPL requires that an SVSM be
present.
Signed-off-by: Tom Lendacky <[email protected]>
Signed-off-by: Borislav Petkov (AMD) <[email protected]>
Link: https://lore.kernel.org/r/4f93f10a2ff3e9f368fd64a5920d51bf38d0c19e.1717600736.git.thomas.lendacky@amd.com
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Some AMD Zen 4 processors support a new feature FAST CPPC which
allows for a faster CPPC loop due to internal architectural
enhancements. The goal of this faster loop is higher performance
at the same power consumption.
Reference:
See the page 99 of PPR for AMD Family 19h Model 61h rev.B1, docID 56713
Signed-off-by: Perry Yuan <[email protected]>
Signed-off-by: Xiaojian Du <[email protected]>
Reviewed-by: Borislav Petkov (AMD) <[email protected]>
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BHI mitigation mode spectre_bhi=auto does not deploy the software
mitigation by default. In a cloud environment, it is a likely scenario
where userspace is trusted but the guests are not trusted. Deploying
system wide mitigation in such cases is not desirable.
Update the auto mode to unconditionally mitigate against malicious
guests. Deploy the software sequence at VMexit in auto mode also, when
hardware mitigation is not available. Unlike the force =on mode,
software sequence is not deployed at syscalls in auto mode.
Suggested-by: Alexandre Chartre <[email protected]>
Signed-off-by: Pawan Gupta <[email protected]>
Signed-off-by: Daniel Sneddon <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Reviewed-by: Alexandre Chartre <[email protected]>
Reviewed-by: Josh Poimboeuf <[email protected]>
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Branch history clearing software sequences and hardware control
BHI_DIS_S were defined to mitigate Branch History Injection (BHI).
Add cmdline spectre_bhi={on|off|auto} to control BHI mitigation:
auto - Deploy the hardware mitigation BHI_DIS_S, if available.
on - Deploy the hardware mitigation BHI_DIS_S, if available,
otherwise deploy the software sequence at syscall entry and
VMexit.
off - Turn off BHI mitigation.
The default is auto mode which does not deploy the software sequence
mitigation. This is because of the hardening done in the syscall
dispatch path, which is the likely target of BHI.
Signed-off-by: Pawan Gupta <[email protected]>
Signed-off-by: Daniel Sneddon <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Reviewed-by: Alexandre Chartre <[email protected]>
Reviewed-by: Josh Poimboeuf <[email protected]>
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Mitigation for BHI is selected based on the bug enumeration. Add bits
needed to enumerate BHI bug.
Signed-off-by: Pawan Gupta <[email protected]>
Signed-off-by: Daniel Sneddon <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Reviewed-by: Alexandre Chartre <[email protected]>
Reviewed-by: Josh Poimboeuf <[email protected]>
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Newer processors supports a hardware control BHI_DIS_S to mitigate
Branch History Injection (BHI). Setting BHI_DIS_S protects the kernel
from userspace BHI attacks without having to manually overwrite the
branch history.
Define MSR_SPEC_CTRL bit BHI_DIS_S and its enumeration CPUID.BHI_CTRL.
Mitigation is enabled later.
Signed-off-by: Daniel Sneddon <[email protected]>
Signed-off-by: Pawan Gupta <[email protected]>
Signed-off-by: Daniel Sneddon <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Reviewed-by: Alexandre Chartre <[email protected]>
Reviewed-by: Josh Poimboeuf <[email protected]>
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Branch History Injection (BHI) attacks may allow a malicious application to
influence indirect branch prediction in kernel by poisoning the branch
history. eIBRS isolates indirect branch targets in ring0. The BHB can
still influence the choice of indirect branch predictor entry, and although
branch predictor entries are isolated between modes when eIBRS is enabled,
the BHB itself is not isolated between modes.
Alder Lake and new processors supports a hardware control BHI_DIS_S to
mitigate BHI. For older processors Intel has released a software sequence
to clear the branch history on parts that don't support BHI_DIS_S. Add
support to execute the software sequence at syscall entry and VMexit to
overwrite the branch history.
For now, branch history is not cleared at interrupt entry, as malicious
applications are not believed to have sufficient control over the
registers, since previous register state is cleared at interrupt
entry. Researchers continue to poke at this area and it may become
necessary to clear at interrupt entry as well in the future.
This mitigation is only defined here. It is enabled later.
Signed-off-by: Pawan Gupta <[email protected]>
Co-developed-by: Daniel Sneddon <[email protected]>
Signed-off-by: Daniel Sneddon <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Reviewed-by: Alexandre Chartre <[email protected]>
Reviewed-by: Josh Poimboeuf <[email protected]>
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Currently, the LBR code assumes that LBR Freeze is supported on all processors
when X86_FEATURE_AMD_LBR_V2 is available i.e. CPUID leaf 0x80000022[EAX]
bit 1 is set. This is incorrect as the availability of the feature is
additionally dependent on CPUID leaf 0x80000022[EAX] bit 2 being set,
which may not be set for all Zen 4 processors.
Define a new feature bit for LBR and PMC freeze and set the freeze enable bit
(FLBRI) in DebugCtl (MSR 0x1d9) conditionally.
It should still be possible to use LBR without freeze for profile-guided
optimization of user programs by using an user-only branch filter during
profiling. When the user-only filter is enabled, branches are no longer
recorded after the transition to CPL 0 upon PMI arrival. When branch
entries are read in the PMI handler, the branch stack does not change.
E.g.
$ perf record -j any,u -e ex_ret_brn_tkn ./workload
Since the feature bit is visible under flags in /proc/cpuinfo, it can be
used to determine the feasibility of use-cases which require LBR Freeze
to be supported by the hardware such as profile-guided optimization of
kernels.
Fixes: ca5b7c0d9621 ("perf/x86/amd/lbr: Add LbrExtV2 branch record support")
Signed-off-by: Sandipan Das <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
Link: https://lore.kernel.org/r/69a453c97cfd11c6f2584b19f937fe6df741510f.1711091584.git.sandipan.das@amd.com
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Add a new word for scattered features because all free bits among the
existing Linux-defined auxiliary flags have been exhausted.
Signed-off-by: Sandipan Das <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
Link: https://lore.kernel.org/r/8380d2a0da469a1f0ad75b8954a79fb689599ff6.1711091584.git.sandipan.das@amd.com
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 RFDS mitigation from Dave Hansen:
"RFDS is a CPU vulnerability that may allow a malicious userspace to
infer stale register values from kernel space. Kernel registers can
have all kinds of secrets in them so the mitigation is basically to
wait until the kernel is about to return to userspace and has user
values in the registers. At that point there is little chance of
kernel secrets ending up in the registers and the microarchitectural
state can be cleared.
This leverages some recent robustness fixes for the existing MDS
vulnerability. Both MDS and RFDS use the VERW instruction for
mitigation"
* tag 'rfds-for-linus-2024-03-11' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
KVM/x86: Export RFDS_NO and RFDS_CLEAR to guests
x86/rfds: Mitigate Register File Data Sampling (RFDS)
Documentation/hw-vuln: Add documentation for RFDS
x86/mmio: Disable KVM mitigation when X86_FEATURE_CLEAR_CPU_BUF is set
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 SEV updates from Borislav Petkov:
- Add the x86 part of the SEV-SNP host support.
This will allow the kernel to be used as a KVM hypervisor capable of
running SNP (Secure Nested Paging) guests. Roughly speaking, SEV-SNP
is the ultimate goal of the AMD confidential computing side,
providing the most comprehensive confidential computing environment
up to date.
This is the x86 part and there is a KVM part which did not get ready
in time for the merge window so latter will be forthcoming in the
next cycle.
- Rework the early code's position-dependent SEV variable references in
order to allow building the kernel with clang and -fPIE/-fPIC and
-mcmodel=kernel
- The usual set of fixes, cleanups and improvements all over the place
* tag 'x86_sev_for_v6.9_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (36 commits)
x86/sev: Disable KMSAN for memory encryption TUs
x86/sev: Dump SEV_STATUS
crypto: ccp - Have it depend on AMD_IOMMU
iommu/amd: Fix failure return from snp_lookup_rmpentry()
x86/sev: Fix position dependent variable references in startup code
crypto: ccp: Make snp_range_list static
x86/Kconfig: Remove CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT
Documentation: virt: Fix up pre-formatted text block for SEV ioctls
crypto: ccp: Add the SNP_SET_CONFIG command
crypto: ccp: Add the SNP_COMMIT command
crypto: ccp: Add the SNP_PLATFORM_STATUS command
x86/cpufeatures: Enable/unmask SEV-SNP CPU feature
KVM: SEV: Make AVIC backing, VMSA and VMCB memory allocation SNP safe
crypto: ccp: Add panic notifier for SEV/SNP firmware shutdown on kdump
iommu/amd: Clean up RMP entries for IOMMU pages during SNP shutdown
crypto: ccp: Handle legacy SEV commands when SNP is enabled
crypto: ccp: Handle non-volatile INIT_EX data when SNP is enabled
crypto: ccp: Handle the legacy TMR allocation when SNP is enabled
x86/sev: Introduce an SNP leaked pages list
crypto: ccp: Provide an API to issue SEV and SNP commands
...
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 FRED support from Thomas Gleixner:
"Support for x86 Fast Return and Event Delivery (FRED).
FRED is a replacement for IDT event delivery on x86 and addresses most
of the technical nightmares which IDT exposes:
1) Exception cause registers like CR2 need to be manually preserved
in nested exception scenarios.
2) Hardware interrupt stack switching is suboptimal for nested
exceptions as the interrupt stack mechanism rewinds the stack on
each entry which requires a massive effort in the low level entry
of #NMI code to handle this.
3) No hardware distinction between entry from kernel or from user
which makes establishing kernel context more complex than it needs
to be especially for unconditionally nestable exceptions like NMI.
4) NMI nesting caused by IRET unconditionally reenabling NMIs, which
is a problem when the perf NMI takes a fault when collecting a
stack trace.
5) Partial restore of ESP when returning to a 16-bit segment
6) Limitation of the vector space which can cause vector exhaustion
on large systems.
7) Inability to differentiate NMI sources
FRED addresses these shortcomings by:
1) An extended exception stack frame which the CPU uses to save
exception cause registers. This ensures that the meta information
for each exception is preserved on stack and avoids the extra
complexity of preserving it in software.
2) Hardware interrupt stack switching is non-rewinding if a nested
exception uses the currently interrupt stack.
3) The entry points for kernel and user context are separate and GS
BASE handling which is required to establish kernel context for
per CPU variable access is done in hardware.
4) NMIs are now nesting protected. They are only reenabled on the
return from NMI.
5) FRED guarantees full restore of ESP
6) FRED does not put a limitation on the vector space by design
because it uses a central entry points for kernel and user space
and the CPUstores the entry type (exception, trap, interrupt,
syscall) on the entry stack along with the vector number. The
entry code has to demultiplex this information, but this removes
the vector space restriction.
The first hardware implementations will still have the current
restricted vector space because lifting this limitation requires
further changes to the local APIC.
7) FRED stores the vector number and meta information on stack which
allows having more than one NMI vector in future hardware when the
required local APIC changes are in place.
The series implements the initial FRED support by:
- Reworking the existing entry and IDT handling infrastructure to
accomodate for the alternative entry mechanism.
- Expanding the stack frame to accomodate for the extra 16 bytes FRED
requires to store context and meta information
- Providing FRED specific C entry points for events which have
information pushed to the extended stack frame, e.g. #PF and #DB.
- Providing FRED specific C entry points for #NMI and #MCE
- Implementing the FRED specific ASM entry points and the C code to
demultiplex the events
- Providing detection and initialization mechanisms and the necessary
tweaks in context switching, GS BASE handling etc.
The FRED integration aims for maximum code reuse vs the existing IDT
implementation to the extent possible and the deviation in hot paths
like context switching are handled with alternatives to minimalize the
impact. The low level entry and exit paths are seperate due to the
extended stack frame and the hardware based GS BASE swichting and
therefore have no impact on IDT based systems.
It has been extensively tested on existing systems and on the FRED
simulation and as of now there are no outstanding problems"
* tag 'x86-fred-2024-03-10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (38 commits)
x86/fred: Fix init_task thread stack pointer initialization
MAINTAINERS: Add a maintainer entry for FRED
x86/fred: Fix a build warning with allmodconfig due to 'inline' failing to inline properly
x86/fred: Invoke FRED initialization code to enable FRED
x86/fred: Add FRED initialization functions
x86/syscall: Split IDT syscall setup code into idt_syscall_init()
KVM: VMX: Call fred_entry_from_kvm() for IRQ/NMI handling
x86/entry: Add fred_entry_from_kvm() for VMX to handle IRQ/NMI
x86/entry/calling: Allow PUSH_AND_CLEAR_REGS being used beyond actual entry code
x86/fred: Fixup fault on ERETU by jumping to fred_entrypoint_user
x86/fred: Let ret_from_fork_asm() jmp to asm_fred_exit_user when FRED is enabled
x86/traps: Add sysvec_install() to install a system interrupt handler
x86/fred: FRED entry/exit and dispatch code
x86/fred: Add a machine check entry stub for FRED
x86/fred: Add a NMI entry stub for FRED
x86/fred: Add a debug fault entry stub for FRED
x86/idtentry: Incorporate definitions/declarations of the FRED entries
x86/fred: Make exc_page_fault() work for FRED
x86/fred: Allow single-step trap and NMI when starting a new task
x86/fred: No ESPFIX needed when FRED is enabled
...
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RFDS is a CPU vulnerability that may allow userspace to infer kernel
stale data previously used in floating point registers, vector registers
and integer registers. RFDS only affects certain Intel Atom processors.
Intel released a microcode update that uses VERW instruction to clear
the affected CPU buffers. Unlike MDS, none of the affected cores support
SMT.
Add RFDS bug infrastructure and enable the VERW based mitigation by
default, that clears the affected buffers just before exiting to
userspace. Also add sysfs reporting and cmdline parameter
"reg_file_data_sampling" to control the mitigation.
For details see:
Documentation/admin-guide/hw-vuln/reg-file-data-sampling.rst
Signed-off-by: Pawan Gupta <[email protected]>
Signed-off-by: Dave Hansen <[email protected]>
Reviewed-by: Thomas Gleixner <[email protected]>
Acked-by: Josh Poimboeuf <[email protected]>
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MDS mitigation requires clearing the CPU buffers before returning to
user. This needs to be done late in the exit-to-user path. Current
location of VERW leaves a possibility of kernel data ending up in CPU
buffers for memory accesses done after VERW such as:
1. Kernel data accessed by an NMI between VERW and return-to-user can
remain in CPU buffers since NMI returning to kernel does not
execute VERW to clear CPU buffers.
2. Alyssa reported that after VERW is executed,
CONFIG_GCC_PLUGIN_STACKLEAK=y scrubs the stack used by a system
call. Memory accesses during stack scrubbing can move kernel stack
contents into CPU buffers.
3. When caller saved registers are restored after a return from
function executing VERW, the kernel stack accesses can remain in
CPU buffers(since they occur after VERW).
To fix this VERW needs to be moved very late in exit-to-user path.
In preparation for moving VERW to entry/exit asm code, create macros
that can be used in asm. Also make VERW patching depend on a new feature
flag X86_FEATURE_CLEAR_CPU_BUF.
Reported-by: Alyssa Milburn <[email protected]>
Suggested-by: Andrew Cooper <[email protected]>
Suggested-by: Peter Zijlstra <[email protected]>
Signed-off-by: Pawan Gupta <[email protected]>
Signed-off-by: Dave Hansen <[email protected]>
Link: https://lore.kernel.org/all/20240213-delay-verw-v8-1-a6216d83edb7%40linux.intel.com
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Add CPU feature detection for Secure Encrypted Virtualization with
Secure Nested Paging. This feature adds a strong memory integrity
protection to help prevent malicious hypervisor-based attacks like
data replay, memory re-mapping, and more.
Since enabling the SNP CPU feature imposes a number of additional
requirements on host initialization and handling legacy firmware APIs
for SEV/SEV-ES guests, only introduce the CPU feature bit so that the
relevant handling can be added, but leave it disabled via a
disabled-features mask.
Once all the necessary changes needed to maintain legacy SEV/SEV-ES
support are introduced in subsequent patches, the SNP feature bit will
be unmasked/enabled.
Signed-off-by: Brijesh Singh <[email protected]>
Signed-off-by: Jarkko Sakkinen <[email protected]>
Signed-off-by: Ashish Kalra <[email protected]>
Signed-off-by: Michael Roth <[email protected]>
Signed-off-by: Borislav Petkov (AMD) <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
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Any FRED enabled CPU will always have the following features as its
baseline:
1) LKGS, load attributes of the GS segment but the base address into
the IA32_KERNEL_GS_BASE MSR instead of the GS segment’s descriptor
cache.
2) WRMSRNS, non-serializing WRMSR for faster MSR writes.
Signed-off-by: H. Peter Anvin (Intel) <[email protected]>
Signed-off-by: Xin Li <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Tested-by: Shan Kang <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
|
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WRMSRNS is an instruction that behaves exactly like WRMSR, with
the only difference being that it is not a serializing instruction
by default. Under certain conditions, WRMSRNS may replace WRMSR to
improve performance.
Add its CPU feature bit, opcode to the x86 opcode map, and an
always inline API __wrmsrns() to embed WRMSRNS into the code.
Signed-off-by: Xin Li <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Tested-by: Shan Kang <[email protected]>
Acked-by: Masami Hiramatsu (Google) <[email protected]>
Acked-by: Borislav Petkov (AMD) <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
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Add a synthetic feature flag for Zen5.
Signed-off-by: Borislav Petkov (AMD) <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 TDX updates from Dave Hansen:
"This contains the initial support for host-side TDX support so that
KVM can run TDX-protected guests. This does not include the actual
KVM-side support which will come from the KVM folks. The TDX host
interactions with kexec also needs to be ironed out before this is
ready for prime time, so this code is currently Kconfig'd off when
kexec is on.
The majority of the code here is the kernel telling the TDX module
which memory to protect and handing some additional memory over to it
to use to store TDX module metadata. That sounds pretty simple, but
the TDX architecture is rather flexible and it takes quite a bit of
back-and-forth to say, "just protect all memory, please."
There is also some code tacked on near the end of the series to handle
a hardware erratum. The erratum can make software bugs such as a
kernel write to TDX-protected memory cause a machine check and
masquerade as a real hardware failure. The erratum handling watches
out for these and tries to provide nicer user errors"
* tag 'x86_tdx_for_6.8' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (21 commits)
x86/virt/tdx: Make TDX host depend on X86_MCE
x86/virt/tdx: Disable TDX host support when kexec is enabled
Documentation/x86: Add documentation for TDX host support
x86/mce: Differentiate real hardware #MCs from TDX erratum ones
x86/cpu: Detect TDX partial write machine check erratum
x86/virt/tdx: Handle TDX interaction with sleep and hibernation
x86/virt/tdx: Initialize all TDMRs
x86/virt/tdx: Configure global KeyID on all packages
x86/virt/tdx: Configure TDX module with the TDMRs and global KeyID
x86/virt/tdx: Designate reserved areas for all TDMRs
x86/virt/tdx: Allocate and set up PAMTs for TDMRs
x86/virt/tdx: Fill out TDMRs to cover all TDX memory regions
x86/virt/tdx: Add placeholder to construct TDMRs to cover all TDX memory regions
x86/virt/tdx: Get module global metadata for module initialization
x86/virt/tdx: Use all system memory when initializing TDX module as TDX memory
x86/virt/tdx: Add skeleton to enable TDX on demand
x86/virt/tdx: Add SEAMCALL error printing for module initialization
x86/virt/tdx: Handle SEAMCALL no entropy error in common code
x86/virt/tdx: Make INTEL_TDX_HOST depend on X86_X2APIC
x86/virt/tdx: Define TDX supported page sizes as macros
...
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TDX memory has integrity and confidentiality protections. Violations of
this integrity protection are supposed to only affect TDX operations and
are never supposed to affect the host kernel itself. In other words,
the host kernel should never, itself, see machine checks induced by the
TDX integrity hardware.
Alas, the first few generations of TDX hardware have an erratum. A
partial write to a TDX private memory cacheline will silently "poison"
the line. Subsequent reads will consume the poison and generate a
machine check. According to the TDX hardware spec, neither of these
things should have happened.
Virtually all kernel memory accesses operations happen in full
cachelines. In practice, writing a "byte" of memory usually reads a 64
byte cacheline of memory, modifies it, then writes the whole line back.
Those operations do not trigger this problem.
This problem is triggered by "partial" writes where a write transaction
of less than cacheline lands at the memory controller. The CPU does
these via non-temporal write instructions (like MOVNTI), or through
UC/WC memory mappings. The issue can also be triggered away from the
CPU by devices doing partial writes via DMA.
With this erratum, there are additional things need to be done. To
prepare for those changes, add a CPU bug bit to indicate this erratum.
Note this bug reflects the hardware thus it is detected regardless of
whether the kernel is built with TDX support or not.
Signed-off-by: Kai Huang <[email protected]>
Signed-off-by: Dave Hansen <[email protected]>
Reviewed-by: Kirill A. Shutemov <[email protected]>
Reviewed-by: David Hildenbrand <[email protected]>
Reviewed-by: Dave Hansen <[email protected]>
Link: https://lore.kernel.org/all/20231208170740.53979-17-dave.hansen%40intel.com
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Add a synthetic feature flag specifically for first generation Zen
machines. There's need to have a generic flag for all Zen generations so
make X86_FEATURE_ZEN be that flag.
Fixes: 30fa92832f40 ("x86/CPU/AMD: Add ZenX generations flags")
Suggested-by: Brian Gerst <[email protected]>
Suggested-by: Tom Lendacky <[email protected]>
Signed-off-by: Borislav Petkov (AMD) <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
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Intel Trust Domain Extensions (TDX) protects guest VMs from malicious
host and certain physical attacks. A CPU-attested software module
called 'the TDX module' runs inside a new isolated memory range as a
trusted hypervisor to manage and run protected VMs.
Pre-TDX Intel hardware has support for a memory encryption architecture
called MKTME. The memory encryption hardware underpinning MKTME is also
used for Intel TDX. TDX ends up "stealing" some of the physical address
space from the MKTME architecture for crypto-protection to VMs. The
BIOS is responsible for partitioning the "KeyID" space between legacy
MKTME and TDX. The KeyIDs reserved for TDX are called 'TDX private
KeyIDs' or 'TDX KeyIDs' for short.
During machine boot, TDX microcode verifies that the BIOS programmed TDX
private KeyIDs consistently and correctly programmed across all CPU
packages. The MSRs are locked in this state after verification. This
is why MSR_IA32_MKTME_KEYID_PARTITIONING gets used for TDX enumeration:
it indicates not just that the hardware supports TDX, but that all the
boot-time security checks passed.
The TDX module is expected to be loaded by the BIOS when it enables TDX,
but the kernel needs to properly initialize it before it can be used to
create and run any TDX guests. The TDX module will be initialized by
the KVM subsystem when KVM wants to use TDX.
Detect platform TDX support by detecting TDX private KeyIDs.
The TDX module itself requires one TDX KeyID as the 'TDX global KeyID'
to protect its metadata. Each TDX guest also needs a TDX KeyID for its
own protection. Just use the first TDX KeyID as the global KeyID and
leave the rest for TDX guests. If no TDX KeyID is left for TDX guests,
disable TDX as initializing the TDX module alone is useless.
[ dhansen: add X86_FEATURE, replace helper function ]
Signed-off-by: Kai Huang <[email protected]>
Signed-off-by: Dave Hansen <[email protected]>
Reviewed-by: Kirill A. Shutemov <[email protected]>
Reviewed-by: Isaku Yamahata <[email protected]>
Reviewed-by: David Hildenbrand <[email protected]>
Reviewed-by: Dave Hansen <[email protected]>
Reviewed-by: Kuppuswamy Sathyanarayanan <[email protected]>
Link: https://lore.kernel.org/all/20231208170740.53979-1-dave.hansen%40intel.com
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Add X86_FEATURE flags for each Zen generation. They should be used from
now on instead of checking f/m/s.
Signed-off-by: Borislav Petkov (AMD) <[email protected]>
Reviewed-by: Nikolay Borisov <[email protected]>
Acked-by: Thomas Gleixner <[email protected]>
Link: http://lore.kernel.org/r/[email protected]
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AMD does not have the requirement for a synchronization barrier when
acccessing a certain group of MSRs. Do not incur that unnecessary
penalty there.
There will be a CPUID bit which explicitly states that a MFENCE is not
needed. Once that bit is added to the APM, this will be extended with
it.
While at it, move to processor.h to avoid include hell. Untangling that
file properly is a matter for another day.
Some notes on the performance aspect of why this is relevant, courtesy
of Kishon VijayAbraham <[email protected]>:
On a AMD Zen4 system with 96 cores, a modified ipi-bench[1] on a VM
shows x2AVIC IPI rate is 3% to 4% lower than AVIC IPI rate. The
ipi-bench is modified so that the IPIs are sent between two vCPUs in the
same CCX. This also requires to pin the vCPU to a physical core to
prevent any latencies. This simulates the use case of pinning vCPUs to
the thread of a single CCX to avoid interrupt IPI latency.
In order to avoid run-to-run variance (for both x2AVIC and AVIC), the
below configurations are done:
1) Disable Power States in BIOS (to prevent the system from going to
lower power state)
2) Run the system at fixed frequency 2500MHz (to prevent the system
from increasing the frequency when the load is more)
With the above configuration:
*) Performance measured using ipi-bench for AVIC:
Average Latency: 1124.98ns [Time to send IPI from one vCPU to another vCPU]
Cumulative throughput: 42.6759M/s [Total number of IPIs sent in a second from
48 vCPUs simultaneously]
*) Performance measured using ipi-bench for x2AVIC:
Average Latency: 1172.42ns [Time to send IPI from one vCPU to another vCPU]
Cumulative throughput: 40.9432M/s [Total number of IPIs sent in a second from
48 vCPUs simultaneously]
From above, x2AVIC latency is ~4% more than AVIC. However, the expectation is
x2AVIC performance to be better or equivalent to AVIC. Upon analyzing
the perf captures, it is observed significant time is spent in
weak_wrmsr_fence() invoked by x2apic_send_IPI().
With the fix to skip weak_wrmsr_fence()
*) Performance measured using ipi-bench for x2AVIC:
Average Latency: 1117.44ns [Time to send IPI from one vCPU to another vCPU]
Cumulative throughput: 42.9608M/s [Total number of IPIs sent in a second from
48 vCPUs simultaneously]
Comparing the performance of x2AVIC with and without the fix, it can be seen
the performance improves by ~4%.
Performance captured using an unmodified ipi-bench using the 'mesh-ipi' option
with and without weak_wrmsr_fence() on a Zen4 system also showed significant
performance improvement without weak_wrmsr_fence(). The 'mesh-ipi' option ignores
CCX or CCD and just picks random vCPU.
Average throughput (10 iterations) with weak_wrmsr_fence(),
Cumulative throughput: 4933374 IPI/s
Average throughput (10 iterations) without weak_wrmsr_fence(),
Cumulative throughput: 6355156 IPI/s
[1] https://github.com/bytedance/kvm-utils/tree/master/microbenchmark/ipi-bench
Signed-off-by: Borislav Petkov (AMD) <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
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Define an X86_FEATURE_* flag for CPUID.80000021H:EAX.[bit 1], and
advertise the feature to userspace via KVM_GET_SUPPORTED_CPUID.
Per AMD's "Processor Programming Reference (PPR) for AMD Family 19h
Model 61h, Revision B1 Processors (56713-B1-PUB)," this CPUID bit
indicates that a WRMSR to MSR_FS_BASE, MSR_GS_BASE, or
MSR_KERNEL_GS_BASE is non-serializing. This is a change in previously
architected behavior.
Effectively, this CPUID bit is a "defeature" bit, or a reverse
polarity feature bit. When this CPUID bit is clear, the feature
(serialization on WRMSR to any of these three MSRs) is available. When
this CPUID bit is set, the feature is not available.
KVM_GET_SUPPORTED_CPUID must pass this bit through from the underlying
hardware, if it is set. Leaving the bit clear claims that WRMSR to
these three MSRs will be serializing in a guest running under
KVM. That isn't true. Though KVM could emulate the feature by
intercepting writes to the specified MSRs, it does not do so
today. The guest is allowed direct read/write access to these MSRs
without interception, so the innate hardware behavior is preserved
under KVM.
Signed-off-by: Jim Mattson <[email protected]>
Reviewed-by: Maxim Levitsky <[email protected]>
Reviewed-by: Borislav Petkov (AMD) <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Sean Christopherson <[email protected]>
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|
Pull kvm updates from Paolo Bonzini:
"ARM:
- Clean up vCPU targets, always returning generic v8 as the preferred
target
- Trap forwarding infrastructure for nested virtualization (used for
traps that are taken from an L2 guest and are needed by the L1
hypervisor)
- FEAT_TLBIRANGE support to only invalidate specific ranges of
addresses when collapsing a table PTE to a block PTE. This avoids
that the guest refills the TLBs again for addresses that aren't
covered by the table PTE.
- Fix vPMU issues related to handling of PMUver.
- Don't unnecessary align non-stack allocations in the EL2 VA space
- Drop HCR_VIRT_EXCP_MASK, which was never used...
- Don't use smp_processor_id() in kvm_arch_vcpu_load(), but the cpu
parameter instead
- Drop redundant call to kvm_set_pfn_accessed() in user_mem_abort()
- Remove prototypes without implementations
RISC-V:
- Zba, Zbs, Zicntr, Zicsr, Zifencei, and Zihpm support for guest
- Added ONE_REG interface for SATP mode
- Added ONE_REG interface to enable/disable multiple ISA extensions
- Improved error codes returned by ONE_REG interfaces
- Added KVM_GET_REG_LIST ioctl() implementation for KVM RISC-V
- Added get-reg-list selftest for KVM RISC-V
s390:
- PV crypto passthrough enablement (Tony, Steffen, Viktor, Janosch)
Allows a PV guest to use crypto cards. Card access is governed by
the firmware and once a crypto queue is "bound" to a PV VM every
other entity (PV or not) looses access until it is not bound
anymore. Enablement is done via flags when creating the PV VM.
- Guest debug fixes (Ilya)
x86:
- Clean up KVM's handling of Intel architectural events
- Intel bugfixes
- Add support for SEV-ES DebugSwap, allowing SEV-ES guests to use
debug registers and generate/handle #DBs
- Clean up LBR virtualization code
- Fix a bug where KVM fails to set the target pCPU during an IRTE
update
- Fix fatal bugs in SEV-ES intrahost migration
- Fix a bug where the recent (architecturally correct) change to
reinject #BP and skip INT3 broke SEV guests (can't decode INT3 to
skip it)
- Retry APIC map recalculation if a vCPU is added/enabled
- Overhaul emergency reboot code to bring SVM up to par with VMX, tie
the "emergency disabling" behavior to KVM actually being loaded,
and move all of the logic within KVM
- Fix user triggerable WARNs in SVM where KVM incorrectly assumes the
TSC ratio MSR cannot diverge from the default when TSC scaling is
disabled up related code
- Add a framework to allow "caching" feature flags so that KVM can
check if the guest can use a feature without needing to search
guest CPUID
- Rip out the ancient MMU_DEBUG crud and replace the useful bits with
CONFIG_KVM_PROVE_MMU
- Fix KVM's handling of !visible guest roots to avoid premature
triple fault injection
- Overhaul KVM's page-track APIs, and KVMGT's usage, to reduce the
API surface that is needed by external users (currently only
KVMGT), and fix a variety of issues in the process
Generic:
- Wrap kvm_{gfn,hva}_range.pte in a union to allow mmu_notifier
events to pass action specific data without needing to constantly
update the main handlers.
- Drop unused function declarations
Selftests:
- Add testcases to x86's sync_regs_test for detecting KVM TOCTOU bugs
- Add support for printf() in guest code and covert all guest asserts
to use printf-based reporting
- Clean up the PMU event filter test and add new testcases
- Include x86 selftests in the KVM x86 MAINTAINERS entry"
* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (279 commits)
KVM: x86/mmu: Include mmu.h in spte.h
KVM: x86/mmu: Use dummy root, backed by zero page, for !visible guest roots
KVM: x86/mmu: Disallow guest from using !visible slots for page tables
KVM: x86/mmu: Harden TDP MMU iteration against root w/o shadow page
KVM: x86/mmu: Harden new PGD against roots without shadow pages
KVM: x86/mmu: Add helper to convert root hpa to shadow page
drm/i915/gvt: Drop final dependencies on KVM internal details
KVM: x86/mmu: Handle KVM bookkeeping in page-track APIs, not callers
KVM: x86/mmu: Drop @slot param from exported/external page-track APIs
KVM: x86/mmu: Bug the VM if write-tracking is used but not enabled
KVM: x86/mmu: Assert that correct locks are held for page write-tracking
KVM: x86/mmu: Rename page-track APIs to reflect the new reality
KVM: x86/mmu: Drop infrastructure for multiple page-track modes
KVM: x86/mmu: Use page-track notifiers iff there are external users
KVM: x86/mmu: Move KVM-only page-track declarations to internal header
KVM: x86: Remove the unused page-track hook track_flush_slot()
drm/i915/gvt: switch from ->track_flush_slot() to ->track_remove_region()
KVM: x86: Add a new page-track hook to handle memslot deletion
drm/i915/gvt: Don't bother removing write-protection on to-be-deleted slot
KVM: x86: Reject memslot MOVE operations if KVMGT is attached
...
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 shadow stack support from Dave Hansen:
"This is the long awaited x86 shadow stack support, part of Intel's
Control-flow Enforcement Technology (CET).
CET consists of two related security features: shadow stacks and
indirect branch tracking. This series implements just the shadow stack
part of this feature, and just for userspace.
The main use case for shadow stack is providing protection against
return oriented programming attacks. It works by maintaining a
secondary (shadow) stack using a special memory type that has
protections against modification. When executing a CALL instruction,
the processor pushes the return address to both the normal stack and
to the special permission shadow stack. Upon RET, the processor pops
the shadow stack copy and compares it to the normal stack copy.
For more information, refer to the links below for the earlier
versions of this patch set"
Link: https://lore.kernel.org/lkml/[email protected]/
Link: https://lore.kernel.org/lkml/[email protected]/
* tag 'x86_shstk_for_6.6-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (47 commits)
x86/shstk: Change order of __user in type
x86/ibt: Convert IBT selftest to asm
x86/shstk: Don't retry vm_munmap() on -EINTR
x86/kbuild: Fix Documentation/ reference
x86/shstk: Move arch detail comment out of core mm
x86/shstk: Add ARCH_SHSTK_STATUS
x86/shstk: Add ARCH_SHSTK_UNLOCK
x86: Add PTRACE interface for shadow stack
selftests/x86: Add shadow stack test
x86/cpufeatures: Enable CET CR4 bit for shadow stack
x86/shstk: Wire in shadow stack interface
x86: Expose thread features in /proc/$PID/status
x86/shstk: Support WRSS for userspace
x86/shstk: Introduce map_shadow_stack syscall
x86/shstk: Check that signal frame is shadow stack mem
x86/shstk: Check that SSP is aligned on sigreturn
x86/shstk: Handle signals for shadow stack
x86/shstk: Introduce routines modifying shstk
x86/shstk: Handle thread shadow stack
x86/shstk: Add user-mode shadow stack support
...
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KVM: x86: SVM changes for 6.6:
- Add support for SEV-ES DebugSwap, i.e. allow SEV-ES guests to use debug
registers and generate/handle #DBs
- Clean up LBR virtualization code
- Fix a bug where KVM fails to set the target pCPU during an IRTE update
- Fix fatal bugs in SEV-ES intrahost migration
- Fix a bug where the recent (architecturally correct) change to reinject
#BP and skip INT3 broke SEV guests (can't decode INT3 to skip it)
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 mm updates from Dave Hansen:
"A pair of small x86/mm updates. The INVPCID one is purely a cleanup.
The PAT one fixes a real issue, albeit a relatively obscure one
(graphics device passthrough under Xen). The fix also makes the code
much more readable.
Summary:
- Remove unnecessary "INVPCID single" feature tracking
- Include PAT in page protection modify mask"
* tag 'x86_mm_for_6.6-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/mm: Remove "INVPCID single" feature tracking
x86/mm: Fix PAT bit missing from page protection modify mask
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Under certain circumstances, an integer division by 0 which faults, can
leave stale quotient data from a previous division operation on Zen1
microarchitectures.
Do a dummy division 0/1 before returning from the #DE exception handler
in order to avoid any leaks of potentially sensitive data.
Signed-off-by: Borislav Petkov (AMD) <[email protected]>
Cc: <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86/gds fixes from Dave Hansen:
"Mitigate Gather Data Sampling issue:
- Add Base GDS mitigation
- Support GDS_NO under KVM
- Fix a documentation typo"
* tag 'gds-for-linus-2023-08-01' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
Documentation/x86: Fix backwards on/off logic about YMM support
KVM: Add GDS_NO support to KVM
x86/speculation: Add Kconfig option for GDS
x86/speculation: Add force option to GDS mitigation
x86/speculation: Add Gather Data Sampling mitigation
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From: Dave Hansen <[email protected]>
tl;dr: Replace a synthetic X86_FEATURE with a hardware X86_FEATURE
and check of existing per-cpu state.
== Background ==
There are three features in play here:
1. Good old Page Table Isolation (PTI)
2. Process Context IDentifiers (PCIDs) which allow entries from
multiple address spaces to be in the TLB at once.
3. Support for the "Invalidate PCID" (INVPCID) instruction,
specifically the "individual address" mode (aka. mode 0).
When all *three* of these are in place, INVPCID can and should be used
to flush out individual addresses in the PTI user address space.
But there's a wrinkle or two: First, this INVPCID mode is dependent on
CR4.PCIDE. Even if X86_FEATURE_INVPCID==1, the instruction may #GP
without setting up CR4. Second, TLB flushing is done very early, even
before CR4 is fully set up. That means even if PTI, PCID and INVPCID
are supported, there is *still* a window where INVPCID can #GP.
== Problem ==
The current code seems to work, but mostly by chance and there are a
bunch of ways it can go wrong. It's also somewhat hard to follow
since X86_FEATURE_INVPCID_SINGLE is set far away from its lone user.
== Solution ==
Make "INVPCID single" more robust and easier to follow by placing all
the logic in one place. Remove X86_FEATURE_INVPCID_SINGLE.
Make two explicit checks before using INVPCID:
1. Check that the system supports INVPCID itself (boot_cpu_has())
2. Then check the CR4.PCIDE shadow to ensures that the CPU
can safely use INVPCID for individual address invalidation.
The CR4 check *always* works and is not affected by any X86_FEATURE_*
twiddling or inconsistencies between the boot and secondary CPUs.
This has been tested on non-Meltdown hardware by using pti=on and
then flipping PCID and INVPCID support with qemu.
== Aside ==
How does this code even work today? By chance, I think. First, PTI
is initialized around the same time that the boot CPU sets
CR4.PCIDE=1. There are currently no TLB invalidations when PTI=1 but
CR4.PCIDE=0. That means that the X86_FEATURE_INVPCID_SINGLE check is
never even reached.
this_cpu_has() is also very nasty to use in this context because the
boot CPU reaches here before cpu_data(0) has been initialized. It
happens to work for X86_FEATURE_INVPCID_SINGLE since it's a
software-defined feature but it would fall over for a hardware-
derived X86_FEATURE.
Reported-by: Jann Horn <[email protected]>
Signed-off-by: Dave Hansen <[email protected]>
Link: https://lore.kernel.org/all/20230718170630.7922E235%40davehans-spike.ostc.intel.com
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Add support for "DebugSwap for SEV-ES guests", which provides support
for swapping DR[0-3] and DR[0-3]_ADDR_MASK on VMRUN and VMEXIT, i.e.
allows KVM to expose debug capabilities to SEV-ES guests. Without
DebugSwap support, the CPU doesn't save/load most _guest_ debug
registers (except DR6/7), and KVM cannot manually context switch guest
DRs due the VMSA being encrypted.
Enable DebugSwap if and only if the CPU also supports NoNestedDataBp,
which causes the CPU to ignore nested #DBs, i.e. #DBs that occur when
vectoring a #DB. Without NoNestedDataBp, a malicious guest can DoS
the host by putting the CPU into an infinite loop of vectoring #DBs
(see https://bugzilla.redhat.com/show_bug.cgi?id=1278496)
Set the features bit in sev_es_sync_vmsa() which is the last point
when VMSA is not encrypted yet as sev_(es_)init_vmcb() (where the most
init happens) is called not only when VCPU is initialised but also on
intrahost migration when VMSA is encrypted.
Eliminate DR7 intercepts as KVM can't modify guest DR7, and intercepting
DR7 would completely defeat the purpose of enabling DebugSwap.
Make X86_FEATURE_DEBUG_SWAP appear in /proc/cpuinfo (by not adding "") to
let the operator know if the VM can debug.
Signed-off-by: Alexey Kardashevskiy <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Sean Christopherson <[email protected]>
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Add the option to flush IBPB only on VMEXIT in order to protect from
malicious guests but one otherwise trusts the software that runs on the
hypervisor.
Signed-off-by: Borislav Petkov (AMD) <[email protected]>
|
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Add support for the CPUID flag which denotes that the CPU is not
affected by SRSO.
Signed-off-by: Borislav Petkov (AMD) <[email protected]>
|
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Add support for the synthetic CPUID flag which "if this bit is 1,
it indicates that MSR 49h (PRED_CMD) bit 0 (IBPB) flushes all branch
type predictions from the CPU branch predictor."
This flag is there so that this capability in guests can be detected
easily (otherwise one would have to track microcode revisions which is
impossible for guests).
It is also needed only for Zen3 and -4. The other two (Zen1 and -2)
always flush branch type predictions by default.
Signed-off-by: Borislav Petkov (AMD) <[email protected]>
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Add a mitigation for the speculative return address stack overflow
vulnerability found on AMD processors.
The mitigation works by ensuring all RET instructions speculate to
a controlled location, similar to how speculation is controlled in the
retpoline sequence. To accomplish this, the __x86_return_thunk forces
the CPU to mispredict every function return using a 'safe return'
sequence.
To ensure the safety of this mitigation, the kernel must ensure that the
safe return sequence is itself free from attacker interference. In Zen3
and Zen4, this is accomplished by creating a BTB alias between the
untraining function srso_untrain_ret_alias() and the safe return
function srso_safe_ret_alias() which results in evicting a potentially
poisoned BTB entry and using that safe one for all function returns.
In older Zen1 and Zen2, this is accomplished using a reinterpretation
technique similar to Retbleed one: srso_untrain_ret() and
srso_safe_ret().
Signed-off-by: Borislav Petkov (AMD) <[email protected]>
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Gather Data Sampling (GDS) is a hardware vulnerability which allows
unprivileged speculative access to data which was previously stored in
vector registers.
Intel processors that support AVX2 and AVX512 have gather instructions
that fetch non-contiguous data elements from memory. On vulnerable
hardware, when a gather instruction is transiently executed and
encounters a fault, stale data from architectural or internal vector
registers may get transiently stored to the destination vector
register allowing an attacker to infer the stale data using typical
side channel techniques like cache timing attacks.
This mitigation is different from many earlier ones for two reasons.
First, it is enabled by default and a bit must be set to *DISABLE* it.
This is the opposite of normal mitigation polarity. This means GDS can
be mitigated simply by updating microcode and leaving the new control
bit alone.
Second, GDS has a "lock" bit. This lock bit is there because the
mitigation affects the hardware security features KeyLocker and SGX.
It needs to be enabled and *STAY* enabled for these features to be
mitigated against GDS.
The mitigation is enabled in the microcode by default. Disable it by
setting gather_data_sampling=off or by disabling all mitigations with
mitigations=off. The mitigation status can be checked by reading:
/sys/devices/system/cpu/vulnerabilities/gather_data_sampling
Signed-off-by: Daniel Sneddon <[email protected]>
Signed-off-by: Dave Hansen <[email protected]>
Acked-by: Josh Poimboeuf <[email protected]>
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There was never a doubt in my mind that they would not fit into a single
u32 eventually.
Signed-off-by: Borislav Petkov (AMD) <[email protected]>
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The Control-Flow Enforcement Technology contains two related features,
one of which is Shadow Stacks. Future patches will utilize this feature
for shadow stack support in KVM, so add a CPU feature flags for Shadow
Stacks (CPUID.(EAX=7,ECX=0):ECX[bit 7]).
To protect shadow stack state from malicious modification, the registers
are only accessible in supervisor mode. This implementation
context-switches the registers with XSAVES. Make X86_FEATURE_SHSTK depend
on XSAVES.
The shadow stack feature, enumerated by the CPUID bit described above,
encompasses both supervisor and userspace support for shadow stack. In
near future patches, only userspace shadow stack will be enabled. In
expectation of future supervisor shadow stack support, create a software
CPU capability to enumerate kernel utilization of userspace shadow stack
support. This user shadow stack bit should depend on the HW "shstk"
capability and that logic will be implemented in future patches.
Co-developed-by: Yu-cheng Yu <[email protected]>
Signed-off-by: Yu-cheng Yu <[email protected]>
Signed-off-by: Rick Edgecombe <[email protected]>
Signed-off-by: Dave Hansen <[email protected]>
Reviewed-by: Borislav Petkov (AMD) <[email protected]>
Reviewed-by: Kees Cook <[email protected]>
Acked-by: Mike Rapoport (IBM) <[email protected]>
Tested-by: Pengfei Xu <[email protected]>
Tested-by: John Allen <[email protected]>
Tested-by: Kees Cook <[email protected]>
Link: https://lore.kernel.org/all/20230613001108.3040476-9-rick.p.edgecombe%40intel.com
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Pull kvm updates from Paolo Bonzini:
"s390:
- More phys_to_virt conversions
- Improvement of AP management for VSIE (nested virtualization)
ARM64:
- Numerous fixes for the pathological lock inversion issue that
plagued KVM/arm64 since... forever.
- New framework allowing SMCCC-compliant hypercalls to be forwarded
to userspace, hopefully paving the way for some more features being
moved to VMMs rather than be implemented in the kernel.
- Large rework of the timer code to allow a VM-wide offset to be
applied to both virtual and physical counters as well as a
per-timer, per-vcpu offset that complements the global one. This
last part allows the NV timer code to be implemented on top.
- A small set of fixes to make sure that we don't change anything
affecting the EL1&0 translation regime just after having having
taken an exception to EL2 until we have executed a DSB. This
ensures that speculative walks started in EL1&0 have completed.
- The usual selftest fixes and improvements.
x86:
- Optimize CR0.WP toggling by avoiding an MMU reload when TDP is
enabled, and by giving the guest control of CR0.WP when EPT is
enabled on VMX (VMX-only because SVM doesn't support per-bit
controls)
- Add CR0/CR4 helpers to query single bits, and clean up related code
where KVM was interpreting kvm_read_cr4_bits()'s "unsigned long"
return as a bool
- Move AMD_PSFD to cpufeatures.h and purge KVM's definition
- Avoid unnecessary writes+flushes when the guest is only adding new
PTEs
- Overhaul .sync_page() and .invlpg() to utilize .sync_page()'s
optimizations when emulating invalidations
- Clean up the range-based flushing APIs
- Revamp the TDP MMU's reaping of Accessed/Dirty bits to clear a
single A/D bit using a LOCK AND instead of XCHG, and skip all of
the "handle changed SPTE" overhead associated with writing the
entire entry
- Track the number of "tail" entries in a pte_list_desc to avoid
having to walk (potentially) all descriptors during insertion and
deletion, which gets quite expensive if the guest is spamming
fork()
- Disallow virtualizing legacy LBRs if architectural LBRs are
available, the two are mutually exclusive in hardware
- Disallow writes to immutable feature MSRs (notably
PERF_CAPABILITIES) after KVM_RUN, similar to CPUID features
- Overhaul the vmx_pmu_caps selftest to better validate
PERF_CAPABILITIES
- Apply PMU filters to emulated events and add test coverage to the
pmu_event_filter selftest
- AMD SVM:
- Add support for virtual NMIs
- Fixes for edge cases related to virtual interrupts
- Intel AMX:
- Don't advertise XTILE_CFG in KVM_GET_SUPPORTED_CPUID if
XTILE_DATA is not being reported due to userspace not opting in
via prctl()
- Fix a bug in emulation of ENCLS in compatibility mode
- Allow emulation of NOP and PAUSE for L2
- AMX selftests improvements
- Misc cleanups
MIPS:
- Constify MIPS's internal callbacks (a leftover from the hardware
enabling rework that landed in 6.3)
Generic:
- Drop unnecessary casts from "void *" throughout kvm_main.c
- Tweak the layout of "struct kvm_mmu_memory_cache" to shrink the
struct size by 8 bytes on 64-bit kernels by utilizing a padding
hole
Documentation:
- Fix goof introduced by the conversion to rST"
* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (211 commits)
KVM: s390: pci: fix virtual-physical confusion on module unload/load
KVM: s390: vsie: clarifications on setting the APCB
KVM: s390: interrupt: fix virtual-physical confusion for next alert GISA
KVM: arm64: Have kvm_psci_vcpu_on() use WRITE_ONCE() to update mp_state
KVM: arm64: Acquire mp_state_lock in kvm_arch_vcpu_ioctl_vcpu_init()
KVM: selftests: Test the PMU event "Instructions retired"
KVM: selftests: Copy full counter values from guest in PMU event filter test
KVM: selftests: Use error codes to signal errors in PMU event filter test
KVM: selftests: Print detailed info in PMU event filter asserts
KVM: selftests: Add helpers for PMC asserts in PMU event filter test
KVM: selftests: Add a common helper for the PMU event filter guest code
KVM: selftests: Fix spelling mistake "perrmited" -> "permitted"
KVM: arm64: vhe: Drop extra isb() on guest exit
KVM: arm64: vhe: Synchronise with page table walker on MMU update
KVM: arm64: pkvm: Document the side effects of kvm_flush_dcache_to_poc()
KVM: arm64: nvhe: Synchronise with page table walker on TLBI
KVM: arm64: Handle 32bit CNTPCTSS traps
KVM: arm64: nvhe: Synchronise with page table walker on vcpu run
KVM: arm64: vgic: Don't acquire its_lock before config_lock
KVM: selftests: Add test to verify KVM's supported XCR0
...
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KVM SVM changes for 6.4:
- Add support for virtual NMIs
- Fixes for edge cases related to virtual interrupts
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Use a common X86_FEATURE_* flag for AMD's PSFD, and suppress it from
/proc/cpuinfo via the standard method of an empty string instead of
hacking in a one-off "private" #define in KVM. The request that led to
KVM defining its own flag was really just that the feature not show up
in /proc/cpuinfo, and additional patches+discussions in the interim have
clarified that defining flags in cpufeatures.h purely so that KVM can
advertise features to userspace is ok so long as the kernel already uses
a word to track the associated CPUID leaf.
No functional change intended.
Link: https://lore.kernel.org/all/[email protected]
Link: https://lore.kernel.org/all/[email protected]
Link: https://lore.kernel.org/all/Y3O7UYWfOLfJkwM%[email protected]
Reviewed-by: Paolo Bonzini <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Sean Christopherson <[email protected]>
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The existing X86_FEATURE_VNMI is a synthetic feature flag that exists
purely to maintain /proc/cpuinfo's ABI, the "real" Intel vNMI feature flag
is tracked as VMX_FEATURE_VIRTUAL_NMIS, as the feature is enumerated
through VMX MSRs, not CPUID.
AMD is also gaining virtual NMI support, but in true VMX vs. SVM form,
enumerates support through CPUID, i.e. wants to add real feature flag for
vNMI.
Redefine the syntheic X86_FEATURE_VNMI to AMD's real CPUID bit to avoid
having both X86_FEATURE_VNMI and e.g. X86_FEATURE_AMD_VNMI.
Signed-off-by: Sean Christopherson <[email protected]>
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