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

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Date:   Tue, 11 Apr 2023 16:25:28 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     "Michael Kelley (LINUX)" <mikelley@...rosoft.com>
Cc:     Juergen Gross <jgross@...e.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 Tue, Apr 11, 2023 at 01:59:36PM +0000, Michael Kelley (LINUX) wrote:
> That's doesn't work.  Hyper-V guests with vTOM don't have
> CC_ATTR_GUEST_SEV_SNP. As previously discussed, the SEV-SNP
> machinery is handled by the paravisor,

Do you see now why I want for all kinds of guest types to not deviate
from doing the proper/default checks for their type? This is a good
example, case-in-point.

All "special" guests would get broken in the future, otherwise.

> I really wanted to avoid calls to hv_is_isolation_supported() outside
> of Hyper-V specific code in the kernel.  The alternative is to create
> another CC_ATTR_ value that is set in the vTOM case, but that reopens
> the naming can-of-worms.

Now is the time for you to settle on what would be the official way to
query those guest types, before it propagates everywhere.

-- 
Regards/Gruss,
    Boris.

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