linux-kernel - Re: [PATCH v3 RESEND] x86/mm: Fix PAT bit missing from page protection modify mask

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Message-ID: <21945539.EfDdHjke4D@jkrzyszt-mobl2.ger.corp.intel.com>
Date:   Mon, 17 Jul 2023 11:42:13 +0200
From:   Janusz Krzysztofik <janusz.krzysztofik@...ux.intel.com>
To:     Dave Hansen <dave.hansen@...ux.intel.com>,
        Borislav Petkov <bp@...en8.de>
Cc:     x86@...nel.org, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Juergen Gross <jgross@...e.com>,
        Andi Shyti <andi.shyti@...ux.intel.com>,
        Marek Marczykowski-Górecki 
        <marmarek@...isiblethingslab.com>,
        "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>,
        linux-kernel@...r.kernel.org, intel-gfx@...ts.freedesktop.org
Subject: Re: [PATCH v3 RESEND] x86/mm: Fix PAT bit missing from page protection modify
 mask

Hi Borislav,

On Monday, 10 July 2023 10:05:19 CEST Borislav Petkov wrote:
> On Mon, Jul 10, 2023 at 09:36:14AM +0200, Janusz Krzysztofik wrote:
> > Assume that adding _PAGE_PAT to _PAGE_CHG_MASK doesn't break pte_modify()
> > and its users, and go for it.  Also, add _PAGE_PAT_LARGE to
> 
> That's my only worry.

Let me remind you that v1 was free of concerns on potential breakage of 
pte_modify().  I can update its commit description as Dave requested and 
resubmit if you confirm that it will be reconsidered as a potential solution.

Thanks,
Janusz

> 
> I'd suggest we queue this but not send it to Linus now. Instead, let it
> cook in linux-next for the whole 6.5 release cycle so that it can get at
> least *some* testing.
> 
> Because if we send it now and something else obscure breaks in a weird
> way in his tree, then we'll have to scramble to fix that too and it'll
> be one helluva mess.
> 
> Dave?
> 
>