Re: [PATCH 2/3] x86,mm: drop TLB flush from ptep_set_access_flags

[Rik van Riel]

On 10/26/2012 05:12 PM, Alan Cox wrote:
> On Fri, 26 Oct 2012 14:45:02 -0400
> Rik van Riel <riel@xxxxxxxxxx> wrote:
>
> > Intel has an architectural guarantee that the TLB entry causing
> > a page fault gets invalidated automatically. This means
> > we should be able to drop the local TLB invalidation.
> >
> > Because of the way other areas of the page fault code work,
> > chances are good that all x86 CPUs do this.  However, if
> > someone somewhere has an x86 CPU that does not invalidate
> > the TLB entry causing a page fault, this one-liner should
> > be easy to revert.
>
> This does not strike me as a good standard of validation for such a change
>
> At the very least we should have an ACK from AMD and from VIA, and
> preferably ping RDC and some of the other embedded folks. Given an AMD
> and VIA ACK I'd be fine. I doubt anyone knows any more what Cyrix CPUs
> did or cared about and I imagine H Peter or Linus can answer for
> Transmeta ;-)

Fair enough.

If it turns out any of those CPUs need an explicit
flush, then we can also adjust flush_tlb_fix_spurious_fault
to actually do a local flush on x86 (or at least on those
CPUs).

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