linux-kernel - Re: [PATCH 4.4 103/105] Revert "x86/mm/pat: Ensure cpa->pfn only contains page frame numbers"

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Message-ID: <1535129126.2902.36.camel@codethink.co.uk>
Date:   Fri, 24 Aug 2018 17:45:26 +0100
From:   Ben Hutchings <ben.hutchings@...ethink.co.uk>
To:     Roland Dreier <roland@...estorage.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     LKML <linux-kernel@...r.kernel.org>, stable@...r.kernel.org,
        matt@...eblueprint.co.uk, bp@...e.de,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andy Lutomirski <luto@...capital.net>, luto@...nel.org,
        ard.biesheuvel@...aro.org, bp@...en8.de, brgerst@...il.com,
        davej@...emonkey.org.uk, dvlasenk@...hat.com,
        "H. Peter Anvin" <hpa@...or.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        sai.praneeth.prakhya@...el.com, sds@...ho.nsa.gov,
        Thomas Gleixner <tglx@...utronix.de>, toshi.kani@...com,
        linux-efi@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
        Yazen.Ghannam@....com
Subject: Re: [PATCH 4.4 103/105] Revert "x86/mm/pat: Ensure cpa->pfn only
 contains page frame numbers"

On Wed, 2018-08-22 at 17:48 -0700, Roland Dreier wrote:
> On Fri, Dec 15, 2017 at 2:20 AM Greg Kroah-Hartman
> > <gregkh@...uxfoundation.org> wrote:
> > This reverts commit 87e2bd898d3a79a8c609f183180adac47879a2a4 which is
> > commit edc3b9129cecd0f0857112136f5b8b1bc1d45918 upstream.
> > 
> > Turns there was too many other issues with this patch to make it viable
> > for the stable tree.
> 
> This was sort of a long time ago, but does anyone remember why this
> needed to be reverted from 4.4?

See
<https://lore.kernel.org/lkml/1512686629.18523.217.camel@codethink.co.uk/T/#u>.

Ben.

> The reason I ask is that without this, commit 02ff2769edbc /
> "x86/mm/pat: Make set_memory_np() L1TF safe" in 4.4.148 is broken.
> That patch has
> 
> -               set_pud(pud, __pud(cpa->pfn | _PAGE_PSE |
> -                                  massage_pgprot(pud_pgprot)));
> +               set_pud(pud, pud_mkhuge(pfn_pud(cpa->pfn,
> +                                  canon_pgprot(pud_pgprot))));
> 
> (and similarly for pmds) but pfn_pud() is operating on page frame
> numbers and __pud(cpa->pfn... in the old code is operating on physical
> addresses.
> 
> This is bad enough that 4.4.148 and all newer 4.4.y crash early in
> boot on some EFI systems that I have.
> 
> For now I am re-applying the "ensure cpa->pfn only contains page frame
> numbers" patch, ported on top of 4.4.151.
> 
>  - R.
> 
-- 
Ben Hutchings, Software Developer                         Codethink Ltd
https://www.codethink.co.uk/                 Dale House, 35 Dale Street
                                     Manchester, M1 2HF, United Kingdom