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SubjectRe: [PATCH 1/5] x86/cpufeatures: Define feature bits to support mitigation of PSF
On Tue, Apr 06, 2021 at 10:50:00AM -0500, Ramakrishna Saripalli wrote:
> diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
> index cc96e26d69f7..21e7f8d0d7d9 100644
> --- a/arch/x86/include/asm/cpufeatures.h
> +++ b/arch/x86/include/asm/cpufeatures.h
> @@ -201,7 +201,7 @@
> #define X86_FEATURE_INVPCID_SINGLE ( 7*32+ 7) /* Effectively INVPCID && CR4.PCIDE=1 */
> #define X86_FEATURE_HW_PSTATE ( 7*32+ 8) /* AMD HW-PState */
> #define X86_FEATURE_PROC_FEEDBACK ( 7*32+ 9) /* AMD ProcFeedbackInterface */
> -/* FREE! ( 7*32+10) */
> +#define X86_FEATURE_PSFD ( 7*32+10) /* Predictive Store Forward Disable */

You don't need this one...

> #define X86_FEATURE_PTI ( 7*32+11) /* Kernel Page Table Isolation enabled */
> #define X86_FEATURE_RETPOLINE ( 7*32+12) /* "" Generic Retpoline mitigation for Spectre variant 2 */
> #define X86_FEATURE_RETPOLINE_AMD ( 7*32+13) /* "" AMD Retpoline mitigation for Spectre variant 2 */
> @@ -309,6 +309,7 @@
> #define X86_FEATURE_AMD_SSBD (13*32+24) /* "" Speculative Store Bypass Disable */
> #define X86_FEATURE_VIRT_SSBD (13*32+25) /* Virtualized Speculative Store Bypass Disable */
> #define X86_FEATURE_AMD_SSB_NO (13*32+26) /* "" Speculative Store Bypass is fixed in hardware. */
> +#define X86_FEATURE_AMD_PSFD (13*32+28) /* "" Predictive Store Forward Disable */

... when you have this one. And this one is AMD-specific so you can just
as well call it X86_FEATURE_PSFD and remove the "".

>
> /* Thermal and Power Management Leaf, CPUID level 0x00000006 (EAX), word 14 */
> #define X86_FEATURE_DTHERM (14*32+ 0) /* Digital Thermal Sensor */
> @@ -428,5 +429,6 @@
> #define X86_BUG_TAA X86_BUG(22) /* CPU is affected by TSX Async Abort(TAA) */
> #define X86_BUG_ITLB_MULTIHIT X86_BUG(23) /* CPU may incur MCE during certain page attribute changes */
> #define X86_BUG_SRBDS X86_BUG(24) /* CPU may leak RNG bits if not mitigated */
> +#define X86_BUG_PSF X86_BUG(25) /* CPU is affected by Predictive Store Forwarding attack */

And I think you don't need this one either if we do a "light" controls
thing but lemme look at the rest first.

Thx.

--
Regards/Gruss,
Boris.

https://people.kernel.org/tglx/notes-about-netiquette

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