linux-kernel - Re: [PATCH v2 2/8] x86/mtrr: support setting MTRR state for software defined MTRRs

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Date:   Thu, 16 Feb 2023 13:19:22 +0100
From:   Juergen Gross <jgross@...e.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        lists@...dbynature.de, mikelley@...rosoft.com,
        torvalds@...ux-foundation.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 v2 2/8] x86/mtrr: support setting MTRR state for software
 defined MTRRs

On 16.02.23 12:25, Borislav Petkov wrote:
> On Thu, Feb 16, 2023 at 10:32:28AM +0100, Juergen Gross wrote:
>> Is that flag _really_ meant to indicate we are running as a SEV-SNP guest?
> 
> Yes.
> 
>> Given that the referenced patch is part of the SEV-SNP host support series,
>> I'm inclined to suspect it won't be set for sure in HyperV SEV-SNP guests.
> 
> It better be. If it is a modified guest - no matter how modified - it
> should set that flag. The vTOM thing is still being discussed.
> 
>> And who is setting it for KVM SEV-SNP guests?
> 
> That same patch does.

Hmm, I must be blind. I can't spot it.

I'm seeing only the feature bit #define and a call of
setup_clear_cpu_cap(X86_FEATURE_SEV_SNP) in this patch.

Or is it done by hardware or the hypervisor?


Juergen

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