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2024-10-26KVM: arm64: Don't retire aborted MMIO instructionOliver Upton1-2/+30
Returning an abort to the guest for an unsupported MMIO access is a documented feature of the KVM UAPI. Nevertheless, it's clear that this plumbing has seen limited testing, since userspace can trivially cause a WARN in the MMIO return: WARNING: CPU: 0 PID: 30558 at arch/arm64/include/asm/kvm_emulate.h:536 kvm_handle_mmio_return+0x46c/0x5c4 arch/arm64/include/asm/kvm_emulate.h:536 Call trace: kvm_handle_mmio_return+0x46c/0x5c4 arch/arm64/include/asm/kvm_emulate.h:536 kvm_arch_vcpu_ioctl_run+0x98/0x15b4 arch/arm64/kvm/arm.c:1133 kvm_vcpu_ioctl+0x75c/0xa78 virt/kvm/kvm_main.c:4487 __do_sys_ioctl fs/ioctl.c:51 [inline] __se_sys_ioctl fs/ioctl.c:893 [inline] __arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:893 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline] invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49 el0_svc_common+0x1e0/0x23c arch/arm64/kernel/syscall.c:132 do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151 el0_svc+0x38/0x68 arch/arm64/kernel/entry-common.c:712 el0t_64_sync_handler+0x90/0xfc arch/arm64/kernel/entry-common.c:730 el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:598 The splat is complaining that KVM is advancing PC while an exception is pending, i.e. that KVM is retiring the MMIO instruction despite a pending synchronous external abort. Womp womp. Fix the glaring UAPI bug by skipping over all the MMIO emulation in case there is a pending synchronous exception. Note that while userspace is capable of pending an asynchronous exception (SError, IRQ, or FIQ), it is still safe to retire the MMIO instruction in this case as (1) they are by definition asynchronous, and (2) KVM relies on hardware support for pending/delivering these exceptions instead of the software state machine for advancing PC. Cc: [email protected] Fixes: da345174ceca ("KVM: arm/arm64: Allow user injection of external data aborts") Reported-by: Alexander Potapenko <[email protected]> Reviewed-by: Marc Zyngier <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Oliver Upton <[email protected]>
2024-05-01KVM: arm64: Force injection of a data abort on NISV MMIO exitMarc Zyngier1-0/+8
If a vcpu exits for a data abort with an invalid syndrome, the expectations are that userspace has a chance to save the day if it has requested to see such exits. However, this is completely futile in the case of a protected VM, as none of the state is available. In this particular case, inject a data abort directly into the vcpu, consistent with what userspace could do. This also helps with pKVM, which discards all syndrome information when forwarding data aborts that are not known to be MMIO. Finally, document this tweak to the API. Signed-off-by: Fuad Tabba <[email protected]> Acked-by: Oliver Upton <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Marc Zyngier <[email protected]>
2024-05-01KVM: arm64: Change kvm_handle_mmio_return() return polarityFuad Tabba1-2/+2
Most exit handlers return <= 0 to indicate that the host needs to handle the exit. Make kvm_handle_mmio_return() consistent with the exit handlers in handle_exit(). This makes the code easier to reason about, and makes it easier to add other handlers in future patches. No functional change intended. Signed-off-by: Fuad Tabba <[email protected]> Acked-by: Oliver Upton <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Marc Zyngier <[email protected]>
2023-10-30KVM: arm64: Add tracepoint for MMIO accesses where ISV==0Oliver Upton1-1/+3
It is a pretty well known fact that KVM does not support MMIO emulation without valid instruction syndrome information (ESR_EL2.ISV == 0). The current kvm_pr_unimpl() is pretty useless, as it contains zero context to relate the event to a vCPU. Replace it with a precise tracepoint that dumps the relevant context so the user can make sense of what the guest is doing. Acked-by: Zenghui Yu <[email protected]> Acked-by: Marc Zyngier <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Oliver Upton <[email protected]>
2022-03-18KVM: arm64: Generalise VM features into a set of flagsMarc Zyngier1-1/+2
We currently deal with a set of booleans for VM features, while they could be better represented as set of flags contained in an unsigned long, similarily to what we are doing on the CPU side. Signed-off-by: Marc Zyngier <[email protected]> [Oliver: Flag-ify the 'ran_once' boolean] Signed-off-by: Oliver Upton <[email protected]> Signed-off-by: Marc Zyngier <[email protected]> Link: https://lore.kernel.org/r/[email protected]
2020-11-10KVM: arm64: Make kvm_skip_instr() and co private to HYPMarc Zyngier1-1/+1
In an effort to remove the vcpu PC manipulations from EL1 on nVHE systems, move kvm_skip_instr() to be HYP-specific. EL1's intent to increment PC post emulation is now signalled via a flag in the vcpu structure. Signed-off-by: Marc Zyngier <[email protected]>
2020-11-10KVM: arm64: Move kvm_vcpu_trap_il_is32bit into kvm_skip_instr32()Marc Zyngier1-1/+1
There is no need to feed the result of kvm_vcpu_trap_il_is32bit() to kvm_skip_instr(), as only AArch32 has a variable length ISA, and this helper can equally be called from kvm_skip_instr32(), reducing the complexity at all the call sites. Acked-by: Mark Rutland <[email protected]> Signed-off-by: Marc Zyngier <[email protected]>
2020-08-09Merge tag 'kvmarm-5.9' of ↵Paolo Bonzini1-6/+0
git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm into kvm-next-5.6 KVM/arm64 updates for Linux 5.9: - Split the VHE and nVHE hypervisor code bases, build the EL2 code separately, allowing for the VHE code to now be built with instrumentation - Level-based TLB invalidation support - Restructure of the vcpu register storage to accomodate the NV code - Pointer Authentication available for guests on nVHE hosts - Simplification of the system register table parsing - MMU cleanups and fixes - A number of post-32bit cleanups and other fixes
2020-07-30KVM: arm64: Move S1PTW S2 fault logic out of io_mem_abort()Will Deacon1-6/+0
To allow for re-injection of stage-2 faults on stage-1 page-table walks due to either a missing or read-only memslot, move the triage logic out of io_mem_abort() and into kvm_handle_guest_abort(), where these aborts can be handled before anything else. Signed-off-by: Will Deacon <[email protected]> Signed-off-by: Marc Zyngier <[email protected]> Cc: Marc Zyngier <[email protected]> Cc: Quentin Perret <[email protected]> Link: https://lore.kernel.org/r/[email protected]
2020-07-10KVM: arm64: clean up redundant 'kvm_run' parametersTianjia Zhang1-5/+6
In the current kvm version, 'kvm_run' has been included in the 'kvm_vcpu' structure. For historical reasons, many kvm-related function parameters retain the 'kvm_run' and 'kvm_vcpu' parameters at the same time. This patch does a unified cleanup of these remaining redundant parameters. Signed-off-by: Tianjia Zhang <[email protected]> Reviewed-by: Vitaly Kuznetsov <[email protected]> Message-Id: <[email protected]> Signed-off-by: Paolo Bonzini <[email protected]>
2020-05-16KVM: Fix spelling in code commentsFuad Tabba1-1/+1
Fix spelling and typos (e.g., repeated words) in comments. Signed-off-by: Fuad Tabba <[email protected]> Signed-off-by: Marc Zyngier <[email protected]> Link: https://lore.kernel.org/r/[email protected]
2020-05-16KVM: arm64: Move virt/kvm/arm to arch/arm64Marc Zyngier1-0/+200
Now that the 32bit KVM/arm host is a distant memory, let's move the whole of the KVM/arm64 code into the arm64 tree. As they said in the song: Welcome Home (Sanitarium). Signed-off-by: Marc Zyngier <[email protected]> Acked-by: Will Deacon <[email protected]> Link: https://lore.kernel.org/r/[email protected]
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