linux-kernel - Re: [PATCH 2/3] x86/cpu/amd: Add feature bit for MSR_AMD64_LS

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Date:   Tue, 8 Nov 2022 19:54:01 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Pavel Machek <pavel@....cz>,
        Andrew Cooper <Andrew.Cooper3@...rix.com>, degoede@...hat.com,
        linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        Daniel Sneddon <daniel.sneddon@...ux.intel.com>,
        antonio.gomez.iglesias@...ux.intel.com
Subject: Re: [PATCH 2/3] x86/cpu/amd: Add feature bit for MSR_AMD64_LS_CFG
 enumeration

On Mon, Sep 12, 2022 at 04:40:47PM -0700, Pawan Gupta wrote:
> Currently there is no easy way to enumerate MSR_AMD64_LS_CFG. As this
> MSR is supported on AMD CPU families 10h to 18h, set a new feature bit
> on these CPU families. The new bit can be used to detect the MSR
> support.
> 
> Suggested-by: Andrew Cooper <andrew.cooper3@...rix.com>
> Signed-off-by: Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>
> ---
>  arch/x86/include/asm/cpufeatures.h | 1 +
>  arch/x86/kernel/cpu/amd.c          | 3 +++
>  2 files changed, 4 insertions(+)
> 
> diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
> index dd173733e40d..90bdb1d98531 100644
> --- a/arch/x86/include/asm/cpufeatures.h
> +++ b/arch/x86/include/asm/cpufeatures.h
> @@ -305,6 +305,7 @@
>  #define X86_FEATURE_USE_IBPB_FW		(11*32+16) /* "" Use IBPB during runtime firmware calls */
>  #define X86_FEATURE_RSB_VMEXIT_LITE	(11*32+17) /* "" Fill RSB on VM exit when EIBRS is enabled */
>  #define X86_FEATURE_MSR_TSX_CTRL	(11*32+18) /* "" MSR IA32_TSX_CTRL */
> +#define X86_FEATURE_MSR_LS_CFG		(11*32+19) /* "" MSR AMD64_LS_CFG */

We already have that one:

#define X86_FEATURE_LS_CFG_SSBD         ( 7*32+24)  /* "" AMD SSBD implementation via LS_CFG MSR */

-- 
Regards/Gruss,
    Boris.

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