lkml.org 
[lkml]   [2022]   [Nov]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 2/3] x86/cpu/amd: Add feature bit for MSR_AMD64_LS_CFG enumeration
On Wed, Nov 09, 2022 at 09:37:20AM -0800, Pawan Gupta wrote:
> Looks like we need to restore this MSR too,

Why do we? Is that MSR read-only too or what is the reason for that one?

> and we can use existing X86_FEATURE_XMM2 to enumerate it.

Or 86_FEATURE_LFENCE_RDTSC.

> If SSBD is the only reason to restore MSR_AMD64_LS_CFG then we should
> be able to use X86_FEATURE_LS_CFG_SSBD for enumeration.

Yes, MSR_AMD64_LS_CFG is used in SSBD mitigations. For everything <= 0x12:

/* AMD Family 0xf - 0x12 */
VULNWL_AMD(0x0f, NO_MELTDOWN | NO_SSB | NO_L1TF | NO_MDS | NO_SWAPGS | NO_ITLB_MULTIHIT | NO_MMIO),
VULNWL_AMD(0x10, NO_MELTDOWN | NO_SSB | NO_L1TF | NO_MDS | NO_SWAPGS | NO_ITLB_MULTIHIT | NO_MMIO),
VULNWL_AMD(0x11, NO_MELTDOWN | NO_SSB | NO_L1TF | NO_MDS | NO_SWAPGS | NO_ITLB_MULTIHIT | NO_MMIO),
VULNWL_AMD(0x12, NO_MELTDOWN | NO_SSB | NO_L1TF | NO_MDS | NO_SWAPGS | NO_ITLB_MULTIHIT | NO_MMIO),

On F14h it says here:

[ 0.278930] Speculative Store Bypass: Vulnerable

simply because it is not present there.

--
Regards/Gruss,
Boris.

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

\
 
 \ /
  Last update: 2022-11-09 19:36    [W:0.092 / U:0.092 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site