Messages in this thread | | | Date | Tue, 3 Apr 2018 15:30:46 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH] mm/migrate: properly preserve write attribute in special migrate entry |
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On Sun, 1 Apr 2018 22:35:06 -0400 jglisse@redhat.com wrote:
> From: Ralph Campbell <rcampbell@nvidia.com> > > Use of pte_write(pte) is only valid for present pte, the common code > which set the migration entry can be reach for both valid present > pte and special swap entry (for device memory). Fix the code to use > the mpfn value which properly handle both cases. > > On x86 this did not have any bad side effect because pte write bit > is below PAGE_BIT_GLOBAL and thus special swap entry have it set to > 0 which in turn means we were always creating read only special > migration entry.
Does this mean that the patch only affects behaviour of non-x86 systems?
> So once migration did finish we always write protected the CPU page > table entry (moreover this is only an issue when migrating from device > memory to system memory). End effect is that CPU write access would > fault again and restore write permission.
That sounds a bit serious. Was a -stable backport considered?
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