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If we're going to provide the encoding for 'pause' in cpu_relax()
anyway, then we can drop the toolchain checks and just always use
it. The advantage of doing this is that other code that need
pause don't need to also define it (yes, another use is coming).
Add the definition to insn-def.h since it's an instruction
definition and also because insn-def.h doesn't include much, so
it's safe to include from asm/vdso/processor.h without concern for
circular dependencies.
Signed-off-by: Andrew Jones <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Palmer Dabbelt <[email protected]>
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Actually it is a part of Conor's
commit aae538cd03bc ("riscv: fix detection of toolchain
Zihintpause support").
It is looks like a merge issue. Samuel's
commit 0b1d60d6dd9e ("riscv: Fix build with
CONFIG_CC_OPTIMIZE_FOR_SIZE=y") do not base on Conor's commit and
revert to __riscv_zihintpause. So this patch can fix it.
Signed-off-by: Minda Chen <[email protected]>
Fixes: 3c349eacc559 ("Merge patch "riscv: Fix build with CONFIG_CC_OPTIMIZE_FOR_SIZE=y"")
Reviewed-by: Conor Dooley <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Cc: [email protected]
Signed-off-by: Palmer Dabbelt <[email protected]>
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Add a vDSO function __vdso_riscv_hwprobe, which can sit in front of the
riscv_hwprobe syscall and answer common queries. We stash a copy of
static answers for the "all CPUs" case in the vDSO data page. This data
is private to the vDSO, so we can decide later to change what's stored
there or under what conditions we defer to the syscall. Currently all
data can be discovered at boot, so the vDSO function answers all queries
when the cpumask is set to the "all CPUs" hint.
There's also a boolean in the data that lets the vDSO function know that
all CPUs are the same. In that case, the vDSO will also answer queries
for arbitrary CPU masks in addition to the "all CPUs" hint.
Signed-off-by: Evan Green <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Palmer Dabbelt <[email protected]>
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This is a single fix, but it conflicts with some recent features. I'm
merging it on top of the commit it fixes to ease backporting.
* b4-shazam-merge:
riscv: Fix build with CONFIG_CC_OPTIMIZE_FOR_SIZE=y
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Palmer Dabbelt <[email protected]>
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commit 8eb060e10185 ("arch/riscv: add Zihintpause support") broke
building with CONFIG_CC_OPTIMIZE_FOR_SIZE enabled (gcc 11.1.0):
CC arch/riscv/kernel/vdso/vgettimeofday.o
In file included from <command-line>:
./arch/riscv/include/asm/jump_label.h: In function 'cpu_relax':
././include/linux/compiler_types.h:285:33: warning: 'asm' operand 0 probably does not match constraints
285 | #define asm_volatile_goto(x...) asm goto(x)
| ^~~
./arch/riscv/include/asm/jump_label.h:41:9: note: in expansion of macro 'asm_volatile_goto'
41 | asm_volatile_goto(
| ^~~~~~~~~~~~~~~~~
././include/linux/compiler_types.h:285:33: error: impossible constraint in 'asm'
285 | #define asm_volatile_goto(x...) asm goto(x)
| ^~~
./arch/riscv/include/asm/jump_label.h:41:9: note: in expansion of macro 'asm_volatile_goto'
41 | asm_volatile_goto(
| ^~~~~~~~~~~~~~~~~
make[1]: *** [scripts/Makefile.build:249: arch/riscv/kernel/vdso/vgettimeofday.o] Error 1
make: *** [arch/riscv/Makefile:128: vdso_prepare] Error 2
Having a static branch in cpu_relax() is problematic because that
function is widely inlined, including in some quite complex functions
like in the VDSO. A quick measurement shows this static branch is
responsible by itself for around 40% of the jump table.
Drop the static branch, which ends up being the same number of
instructions anyway. If Zihintpause is supported, we trade the nop from
the static branch for a div. If Zihintpause is unsupported, we trade the
jump from the static branch for (what gets interpreted as) a nop.
Fixes: 8eb060e10185 ("arch/riscv: add Zihintpause support")
Signed-off-by: Samuel Holland <[email protected]>
Reviewed-by: Conor Dooley <[email protected]>
Cc: [email protected]
Signed-off-by: Palmer Dabbelt <[email protected]>
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It is not sufficient to check if a toolchain supports a particular
extension without checking if the linker supports that extension
too. For example, Clang 15 supports Zihintpause but GNU bintutils
2.35.2 does not, leading build errors like so:
riscv64-linux-gnu-ld: -march=rv64i2p0_m2p0_a2p0_c2p0_zihintpause2p0: Invalid or unknown z ISA extension: 'zihintpause'
Add a TOOLCHAIN_HAS_ZIHINTPAUSE which checks if each of the compiler,
assembler and linker support the extension. Replace the ifdef in the
vdso with one depending on this new symbol.
Fixes: 8eb060e10185 ("arch/riscv: add Zihintpause support")
Signed-off-by: Conor Dooley <[email protected]>
Reviewed-by: Heiko Stuebner <[email protected]>
Reviewed-by: Nathan Chancellor <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Palmer Dabbelt <[email protected]>
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Implement support for the ZiHintPause extension.
The PAUSE instruction is a HINT that indicates the current hart’s rate
of instruction retirement should be temporarily reduced or paused.
Reviewed-by: Heiko Stuebner <[email protected]>
Tested-by: Heiko Stuebner <[email protected]>
Signed-off-by: Dao Lu <[email protected]>
[Palmer: Some minor merge conflicts.]
Link: https://lore.kernel.org/all/[email protected]/
Link: https://lore.kernel.org/all/[email protected]/
Signed-off-by: Palmer Dabbelt <[email protected]>
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Implement generic vdso time namespace support which also enables time
namespaces for riscv. This is quite similar to what arm64 does.
selftest/timens test result:
1..10
ok 1 Passed for CLOCK_BOOTTIME (syscall)
ok 2 Passed for CLOCK_BOOTTIME (vdso)
ok 3 # SKIP CLOCK_BOOTTIME_ALARM isn't supported
ok 4 # SKIP CLOCK_BOOTTIME_ALARM isn't supported
ok 5 Passed for CLOCK_MONOTONIC (syscall)
ok 6 Passed for CLOCK_MONOTONIC (vdso)
ok 7 Passed for CLOCK_MONOTONIC_COARSE (syscall)
ok 8 Passed for CLOCK_MONOTONIC_COARSE (vdso)
ok 9 Passed for CLOCK_MONOTONIC_RAW (syscall)
ok 10 Passed for CLOCK_MONOTONIC_RAW (vdso)
# Totals: pass:8 fail:0 xfail:0 xpass:0 skip:2 error:0
Signed-off-by: Tong Tiangen <[email protected]>
Signed-off-by: Palmer Dabbelt <[email protected]>
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riscv's <vdso/processor.h> uses barrier() so it should include
<asm/barrier.h>
Fixes this build error:
CC [M] drivers/net/ethernet/emulex/benet/be_main.o
In file included from ./include/vdso/processor.h:10,
from ./arch/riscv/include/asm/processor.h:11,
from ./include/linux/prefetch.h:15,
from drivers/net/ethernet/emulex/benet/be_main.c:14:
./arch/riscv/include/asm/vdso/processor.h: In function 'cpu_relax':
./arch/riscv/include/asm/vdso/processor.h:14:2: error: implicit declaration of function 'barrier' [-Werror=implicit-function-declaration]
14 | barrier();
This happens with a total of 5 networking drivers -- they all use
<linux/prefetch.h>.
rv64 allmodconfig now builds cleanly after this patch.
Fixes fallout from:
815f0ddb346c ("include/linux/compiler*.h: make compiler-*.h mutually exclusive")
Fixes: ad5d1122b82f ("riscv: use vDSO common flow to reduce the latency of the time-related functions")
Reported-by: Andreas Schwab <[email protected]>
Signed-off-by: Randy Dunlap <[email protected]>
Acked-by: Arvind Sankar <[email protected]>
Signed-off-by: Palmer Dabbelt <[email protected]>
Reviewed-by: Nick Desaulniers <[email protected]>
Signed-off-by: Palmer Dabbelt <[email protected]>
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MIPS already uses and S390 will need the vdso data pointer in
__arch_get_hw_counter().
This works nicely as long as the architecture does not support time
namespaces in the VDSO. With time namespaces enabled the regular
accessor to the vdso data pointer __arch_get_vdso_data() will return the
namespace specific VDSO data page for tasks which are part of a
non-root time namespace. This would cause the architectures which need
the vdso data pointer in __arch_get_hw_counter() to access the wrong
vdso data page.
Add a vdso_data pointer argument to __arch_get_hw_counter() and hand it in
from the call sites in the core code. For architectures which do not need
the data pointer in their counter accessor function the compiler will just
optimize it out.
Fix up all existing architecture implementations and make MIPS utilize the
pointer instead of invoking the accessor function.
No functional change and no change in the resulting object code (except
MIPS).
Signed-off-by: Thomas Gleixner <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]
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Now that 'smp_read_barrier_depends()' has gone the way of the Norwegian
Blue, drop the inclusion of <asm/barrier.h> in 'asm-generic/rwonce.h'.
This requires fixups to some architecture vdso headers which were
previously relying on 'asm/barrier.h' coming in via 'linux/compiler.h'.
Acked-by: Peter Zijlstra (Intel) <[email protected]>
Signed-off-by: Will Deacon <[email protected]>
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Even if RISC-V has supported the vDSO feature, the latency of the functions
for obtaining the system time is still expensive. It is because these
functions still trigger a corresponding system call in the process, which
slows down the response time. If we want to remove the system call to
reduce the latency, the kernel should have the ability to output the system
clock information to userspace. This patch introduces the vDSO common flow
to enable the kernel to achieve the above feature and uses "rdtime"
instruction to obtain the current time in the user space. Under this
condition, the latency cost by the ecall from U-mode to S-mode can be
eliminated. After applying this patch, the latency of gettimeofday()
measured on the HiFive unleashed board can be reduced by %61.
Signed-off-by: Vincent Chen <[email protected]>
Reviewed-by: Atish Patra <[email protected]>
Signed-off-by: Palmer Dabbelt <[email protected]>
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