tldr; Just FYI, I'm carrying this on the perf tools tree.
Full explanation:
There used to be no copies, with tools/ code using kernel headers
directly. From time to time tools/perf/ broke due to legitimate kernel
hacking. At some point Linus complained about such direct usage. Then we
adopted the current model.
The way these headers are used in perf are not restricted to just
including them to compile something.
There are sometimes used in scripts that convert defines into string
tables, etc, so some change may break one of these scripts, or new MSRs
may use some different #define pattern, etc.
E.g.:
$ ls -1 tools/perf/trace/beauty/*.sh | head -5
tools/perf/trace/beauty/arch_errno_names.sh
tools/perf/trace/beauty/drm_ioctl.sh
tools/perf/trace/beauty/fadvise.sh
tools/perf/trace/beauty/fsconfig.sh
tools/perf/trace/beauty/fsmount.sh
$
$ tools/perf/trace/beauty/fadvise.sh
static const char *fadvise_advices[] = {
[0] = "NORMAL",
[1] = "RANDOM",
[2] = "SEQUENTIAL",
[3] = "WILLNEED",
[4] = "DONTNEED",
[5] = "NOREUSE",
};
$
The tools/perf/check-headers.sh script, part of the tools/ build
process, points out changes in the original files.
So its important not to touch the copies in tools/ when doing changes in
the original kernel headers, that will be done later, when
check-headers.sh inform about the change to the perf tools hackers.
To pick the changes from:
95a6ccbdc7199a14 ("x86/bhi: Mitigate KVM by default")
ec9404e40e8f3642 ("x86/bhi: Add BHI mitigation knob")
be482ff9500999f5 ("x86/bhi: Enumerate Branch History Injection (BHI) bug")
0f4a837615ff925b ("x86/bhi: Define SPEC_CTRL_BHI_DIS_S")
7390db8aea0d64e9 ("x86/bhi: Add support for clearing branch history at syscall entry")
This causes these perf files to be rebuilt and brings some X86_FEATURE
that will be used when updating the copies of
tools/arch/x86/lib/mem{cpy,set}_64.S with the kernel sources:
CC /tmp/build/perf/bench/mem-memcpy-x86-64-asm.o
CC /tmp/build/perf/bench/mem-memset-x86-64-asm.o
And addresses this perf build warning:
Warning: Kernel ABI header differences:
diff -u tools/arch/x86/include/asm/cpufeatures.h arch/x86/include/asm/cpufeatures.h
Cc: Adrian Hunter <[email protected]>
Cc: Daniel Sneddon <[email protected]>
Cc: Ian Rogers <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Pawan Gupta <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>
---
tools/arch/x86/include/asm/cpufeatures.h | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/tools/arch/x86/include/asm/cpufeatures.h b/tools/arch/x86/include/asm/cpufeatures.h
index a38f8f9ba6572912..3c7434329661c66e 100644
--- a/tools/arch/x86/include/asm/cpufeatures.h
+++ b/tools/arch/x86/include/asm/cpufeatures.h
@@ -461,11 +461,15 @@
/*
* Extended auxiliary flags: Linux defined - for features scattered in various
- * CPUID levels like 0x80000022, etc.
+ * CPUID levels like 0x80000022, etc and Linux defined features.
*
* Reuse free bits when adding new feature flags!
*/
#define X86_FEATURE_AMD_LBR_PMC_FREEZE (21*32+ 0) /* AMD LBR and PMC Freeze */
+#define X86_FEATURE_CLEAR_BHB_LOOP (21*32+ 1) /* "" Clear branch history at syscall entry using SW loop */
+#define X86_FEATURE_BHI_CTRL (21*32+ 2) /* "" BHI_DIS_S HW control available */
+#define X86_FEATURE_CLEAR_BHB_HW (21*32+ 3) /* "" BHI_DIS_S HW control enabled */
+#define X86_FEATURE_CLEAR_BHB_LOOP_ON_VMEXIT (21*32+ 4) /* "" Clear branch history at vmexit using SW loop */
/*
* BUG word(s)
@@ -515,4 +519,5 @@
#define X86_BUG_SRSO X86_BUG(1*32 + 0) /* AMD SRSO bug */
#define X86_BUG_DIV0 X86_BUG(1*32 + 1) /* AMD DIV0 speculation bug */
#define X86_BUG_RFDS X86_BUG(1*32 + 2) /* CPU is vulnerable to Register File Data Sampling */
+#define X86_BUG_BHI X86_BUG(1*32 + 3) /* CPU is affected by Branch History Injection */
#endif /* _ASM_X86_CPUFEATURES_H */
--
2.44.0
On Thu, Apr 25, 2024 at 06:19:07PM -0300, Arnaldo Carvalho de Melo wrote:
> tldr; Just FYI, I'm carrying this on the perf tools tree.
Sorry about the subject line, reused from a previous sync, will fix it
up.
- Arnaldo
> Full explanation:
>
> There used to be no copies, with tools/ code using kernel headers
> directly. From time to time tools/perf/ broke due to legitimate kernel
> hacking. At some point Linus complained about such direct usage. Then we
> adopted the current model.
>
> The way these headers are used in perf are not restricted to just
> including them to compile something.
>
> There are sometimes used in scripts that convert defines into string
> tables, etc, so some change may break one of these scripts, or new MSRs
> may use some different #define pattern, etc.
>
> E.g.:
>
> $ ls -1 tools/perf/trace/beauty/*.sh | head -5
> tools/perf/trace/beauty/arch_errno_names.sh
> tools/perf/trace/beauty/drm_ioctl.sh
> tools/perf/trace/beauty/fadvise.sh
> tools/perf/trace/beauty/fsconfig.sh
> tools/perf/trace/beauty/fsmount.sh
> $
> $ tools/perf/trace/beauty/fadvise.sh
> static const char *fadvise_advices[] = {
> [0] = "NORMAL",
> [1] = "RANDOM",
> [2] = "SEQUENTIAL",
> [3] = "WILLNEED",
> [4] = "DONTNEED",
> [5] = "NOREUSE",
> };
> $
>
> The tools/perf/check-headers.sh script, part of the tools/ build
> process, points out changes in the original files.
>
> So its important not to touch the copies in tools/ when doing changes in
> the original kernel headers, that will be done later, when
> check-headers.sh inform about the change to the perf tools hackers.
>
> To pick the changes from:
>
> 95a6ccbdc7199a14 ("x86/bhi: Mitigate KVM by default")
> ec9404e40e8f3642 ("x86/bhi: Add BHI mitigation knob")
> be482ff9500999f5 ("x86/bhi: Enumerate Branch History Injection (BHI) bug")
> 0f4a837615ff925b ("x86/bhi: Define SPEC_CTRL_BHI_DIS_S")
> 7390db8aea0d64e9 ("x86/bhi: Add support for clearing branch history at syscall entry")
>
> This causes these perf files to be rebuilt and brings some X86_FEATURE
> that will be used when updating the copies of
> tools/arch/x86/lib/mem{cpy,set}_64.S with the kernel sources:
>
> CC /tmp/build/perf/bench/mem-memcpy-x86-64-asm.o
> CC /tmp/build/perf/bench/mem-memset-x86-64-asm.o
>
> And addresses this perf build warning:
>
> Warning: Kernel ABI header differences:
> diff -u tools/arch/x86/include/asm/cpufeatures.h arch/x86/include/asm/cpufeatures.h
>
> Cc: Adrian Hunter <[email protected]>
> Cc: Daniel Sneddon <[email protected]>
> Cc: Ian Rogers <[email protected]>
> Cc: Jiri Olsa <[email protected]>
> Cc: Namhyung Kim <[email protected]>
> Cc: Pawan Gupta <[email protected]>
> Cc: Thomas Gleixner <[email protected]>
> Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>
> ---
> tools/arch/x86/include/asm/cpufeatures.h | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/tools/arch/x86/include/asm/cpufeatures.h b/tools/arch/x86/include/asm/cpufeatures.h
> index a38f8f9ba6572912..3c7434329661c66e 100644
> --- a/tools/arch/x86/include/asm/cpufeatures.h
> +++ b/tools/arch/x86/include/asm/cpufeatures.h
> @@ -461,11 +461,15 @@
>
> /*
> * Extended auxiliary flags: Linux defined - for features scattered in various
> - * CPUID levels like 0x80000022, etc.
> + * CPUID levels like 0x80000022, etc and Linux defined features.
> *
> * Reuse free bits when adding new feature flags!
> */
> #define X86_FEATURE_AMD_LBR_PMC_FREEZE (21*32+ 0) /* AMD LBR and PMC Freeze */
> +#define X86_FEATURE_CLEAR_BHB_LOOP (21*32+ 1) /* "" Clear branch history at syscall entry using SW loop */
> +#define X86_FEATURE_BHI_CTRL (21*32+ 2) /* "" BHI_DIS_S HW control available */
> +#define X86_FEATURE_CLEAR_BHB_HW (21*32+ 3) /* "" BHI_DIS_S HW control enabled */
> +#define X86_FEATURE_CLEAR_BHB_LOOP_ON_VMEXIT (21*32+ 4) /* "" Clear branch history at vmexit using SW loop */
>
> /*
> * BUG word(s)
> @@ -515,4 +519,5 @@
> #define X86_BUG_SRSO X86_BUG(1*32 + 0) /* AMD SRSO bug */
> #define X86_BUG_DIV0 X86_BUG(1*32 + 1) /* AMD DIV0 speculation bug */
> #define X86_BUG_RFDS X86_BUG(1*32 + 2) /* CPU is vulnerable to Register File Data Sampling */
> +#define X86_BUG_BHI X86_BUG(1*32 + 3) /* CPU is affected by Branch History Injection */
> #endif /* _ASM_X86_CPUFEATURES_H */
> --
> 2.44.0
>