When AMD introduced "Long Mode Segment Limit Enable" (a.k.a. "VMware
mode"), the feature was not enumerated by a CPUID bit. Now that VMware
has abandoned binary translation, AMD has deprecated EFER.LMSLE.

The absence of the feature *is* now enumerated by a CPUID bit (a la
Intel's X86_FEATURE_ZERO_FCS_DCS and X86_FEATURE_FDP_EXCPTN_ONLY).

This defeature bit is already present in feature word 13, but it was
previously anonymous. Name it X86_FEATURE_NO_LMSLE, so that KVM can
reference it when constructing a supported guest CPUID table.

Since this bit indicates the absence of a feature, don't enumerate it
in /proc/cpuinfo.

Signed-off-by: Jim Mattson <jmattson@google.com>
---
 arch/x86/include/asm/cpufeatures.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index ef4775c6db01..0f5a3285d8d8 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -319,6 +319,7 @@
 #define X86_FEATURE_AMD_IBRS		(13*32+14) /* "" Indirect Branch Restricted Speculation */
 #define X86_FEATURE_AMD_STIBP		(13*32+15) /* "" Single Thread Indirect Branch Predictors */
 #define X86_FEATURE_AMD_STIBP_ALWAYS_ON	(13*32+17) /* "" Single Thread Indirect Branch Predictors always-on preferred */
+#define X86_FEATURE_NO_LMSLE		(13*32+20) /* "" EFER_LMSLE is unsupported */
 #define X86_FEATURE_AMD_PPIN		(13*32+23) /* Protected Processor Inventory Number */
 #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 */
-- 
2.37.3.968.ga6b4b080e4-goog

On Tue, Sep 20, 2022 at 01:59:21PM -0700, Jim Mattson wrote:
> When AMD introduced "Long Mode Segment Limit Enable" (a.k.a. "VMware
> mode"), the feature was not enumerated by a CPUID bit. Now that VMware
> has abandoned binary translation, AMD has deprecated EFER.LMSLE.
> 
> The absence of the feature *is* now enumerated by a CPUID bit (a la
> Intel's X86_FEATURE_ZERO_FCS_DCS and X86_FEATURE_FDP_EXCPTN_ONLY).
> 
> This defeature bit is already present in feature word 13, but it was
> previously anonymous. Name it X86_FEATURE_NO_LMSLE, so that KVM can
> reference it when constructing a supported guest CPUID table.
> 
> Since this bit indicates the absence of a feature, don't enumerate it
> in /proc/cpuinfo.
> 
> Signed-off-by: Jim Mattson <jmattson@google.com>
> ---
>  arch/x86/include/asm/cpufeatures.h | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
> index ef4775c6db01..0f5a3285d8d8 100644
> --- a/arch/x86/include/asm/cpufeatures.h
> +++ b/arch/x86/include/asm/cpufeatures.h
> @@ -319,6 +319,7 @@
>  #define X86_FEATURE_AMD_IBRS		(13*32+14) /* "" Indirect Branch Restricted Speculation */
>  #define X86_FEATURE_AMD_STIBP		(13*32+15) /* "" Single Thread Indirect Branch Predictors */
>  #define X86_FEATURE_AMD_STIBP_ALWAYS_ON	(13*32+17) /* "" Single Thread Indirect Branch Predictors always-on preferred */
> +#define X86_FEATURE_NO_LMSLE		(13*32+20) /* "" EFER_LMSLE is unsupported */
>  #define X86_FEATURE_AMD_PPIN		(13*32+23) /* Protected Processor Inventory Number */
>  #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 */
> -- 

Acked-by: Borislav Petkov <bp@suse.de>

-- 
Regards/Gruss,
    Boris.

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