linux-kernel - Re: [PATCH v5 04/15] x86/mtrr: support setting MTRR state for software defined MTRRs

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Date:   Wed, 12 Apr 2023 10:30:42 +0200
From:   Juergen Gross <jgross@...e.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     "Michael Kelley (LINUX)" <mikelley@...rosoft.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH v5 04/15] x86/mtrr: support setting MTRR state for
 software defined MTRRs

On 11.04.23 19:15, Borislav Petkov wrote:
> On Tue, Apr 11, 2023 at 05:57:07PM +0200, Juergen Gross wrote:
>> Short answer: You asked me to add it in V2 of the series.
>>
>> Longer answer: SEV_SNP guests and TDX guests would cause #VE when writing
>>    MTRR MSRs.
> 
> Ah, sorry. Let's extend the comment then and use your original check:
> 
>         /*
>          * Only allowed for special virtualization cases:
>          * - when running as Hyper-V, SEV-SNP guest using vTOM
>          * - when running as Xen PV guest
>          * - when running as SEV-SNP or TSX guest to avoid unnecessary
> 	*   VMM communication/Virtualization exceptions (#VC, #VE)
>          */
> 	if (!hv_is_isolation_supported() &&
> 	    !cpu_feature_enabled(X86_FEATURE_XENPV) &&
> 	    !cc_platform_has(CC_ATTR_GUEST_SEV_SNP) &&
> 	    !cpu_feature_enabled(X86_FEATURE_TDX_GUEST))
> 		return;

Okay.


Juergen


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