Re: [PATCH v4 1/7] x86/cpu: Define a scattered No Nested Data Breakpoints feature bit
From: Borislav Petkov
Date: Mon Dec 05 2022 - 05:24:42 EST
On Wed, Nov 30, 2022 at 07:49:57PM -0600, Kim Phillips wrote:
> It's a part of the CPUID 0x80000021 leaf, and this allows us to
^^
Please use passive voice in your commit message: no "we" or "I", etc,
and describe your changes in imperative mood.
Personal pronouns are ambiguous in text, especially with so many
parties/companies/etc developing the kernel so let's avoid them please.
> group this and other CPUID 0x80000021 EAX feature bits to being
> propagated via kvm_set_cpu_caps instead of open-coding them in
> __do_cpuid_func().
>
> Signed-off-by: Kim Phillips <kim.phillips@xxxxxxx>
> ---
> arch/x86/include/asm/cpufeatures.h | 1 +
> arch/x86/kernel/cpu/scattered.c | 1 +
> 2 files changed, 2 insertions(+)
>
> diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
> index 11a0e06362e4..b16fdcedc2b5 100644
> --- a/arch/x86/include/asm/cpufeatures.h
> +++ b/arch/x86/include/asm/cpufeatures.h
> @@ -307,6 +307,7 @@
> #define X86_FEATURE_SGX_EDECCSSA (11*32+18) /* "" SGX EDECCSSA user leaf function */
> #define X86_FEATURE_CALL_DEPTH (11*32+19) /* "" Call depth tracking for RSB stuffing */
> #define X86_FEATURE_MSR_TSX_CTRL (11*32+20) /* "" MSR IA32_TSX_CTRL (Intel) implemented */
> +#define X86_FEATURE_NO_NESTED_DATA_BP (11*32+21) /* "" AMD No Nested Data Breakpoints */
Right, what is the use of this bit in a KVM guest? Running perf tool in
a guest would use that bit how?
Thx.
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette