linux-kernel - Re: [PATCH 1/2] x86/pat: fix x86_has_pat

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Message-ID: <ddb0cc0d-cefc-4f33-23f8-3a94c7c51a49@suse.com>
Date:   Mon, 20 Jun 2022 17:34:42 +0200
From:   Juergen Gross <jgross@...e.com>
To:     Dave Hansen <dave.hansen@...el.com>, Borislav Petkov <bp@...en8.de>
Cc:     xen-devel@...ts.xenproject.org, x86@...nel.org,
        linux-kernel@...r.kernel.org, jbeulich@...e.com,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH 1/2] x86/pat: fix x86_has_pat_wp()

On 20.06.22 17:27, Dave Hansen wrote:
> On 6/20/22 03:41, Juergen Gross wrote:
>>> But I'm only guessing - this needs a *lot* more elaboration and
>>> explanation why exactly this is needed.
>>
>> I will correct the code and update the commit message.
> 
> It would also be great to cover the end-user-visible impact of the bug
> and the fix.  It _looks_ like it will probably only affect an SEV
> system's ability to read some EFI data.  That will presumably be pretty
> bad because it ends up reading from an encrypted mapping instead of a
> decrypted one.

Xen doesn't support SEV guests yet. So the only caveat here would be EFI
setting up PAT by itself.

Not sure this is really a real world issue.


Juergen

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