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SubjectRe: [PATCH 1/3] x86/mm: Check for pfn instead of page in vmalloc_sync_one()
On Mon, 15 Jul 2019, Joerg Roedel wrote:
> On Mon, Jul 15, 2019 at 03:08:42PM +0200, Thomas Gleixner wrote:
> > On Mon, 15 Jul 2019, Joerg Roedel wrote:
> >
> > > From: Joerg Roedel <jroedel@suse.de>
> > >
> > > Do not require a struct page for the mapped memory location
> > > because it might not exist. This can happen when an
> > > ioremapped region is mapped with 2MB pages.
> > >
> > > Signed-off-by: Joerg Roedel <jroedel@suse.de>
> >
> > Lacks a Fixes tag, hmm?
>
> Yeah, right, the question is, which commit to put in there. The problem
> results from two changes:
>
> 1) Introduction of !SHARED_KERNEL_PMD path in x86-32. In itself
> this is not a problem, and the path was only enabled for
> Xen-PV.
>
> 2) Huge IORemapings which use the PMD level. Also not a problem
> by itself, but together with !SHARED_KERNEL_PMD problematic
> because it requires to sync the PMD entries between all
> page-tables, and that was not implemented.
>
> Before PTI-x32 was merged this problem did not show up, maybe because
> the 32-bit Xen-PV users did not trigger it. But with PTI-x32 all PAE
> users run with !SHARED_KERNEL_PMD and the problem popped up.
>
> For the last patch I put the PTI-x32 enablement commit in the fixes tag,
> because that was the one that showed up during bisection. But more
> correct would probably be
>
> 5d72b4fba40e ('x86, mm: support huge I/O mapping capability I/F')

Looks about right.

Thanks,

tglx

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