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    SubjectRe: [PATCH 4.4 103/105] Revert "x86/mm/pat: Ensure cpa->pfn only contains page frame numbers"
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    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@linuxfoundation.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

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