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

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Message-ID: <63ccccac-2aa7-8850-9cd3-a8b7b89e1872@intel.com>
Date:   Mon, 20 Jun 2022 08:27:33 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Juergen Gross <jgross@...e.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 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.

The

	pr_warn("failed to early memremap...

is (counterintuitively) what is wanted here.

Right?