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SubjectRe: [patch V3 02/11] x86/mm/cpa: Split, rename and clean up try_preserve_large_page()
On Tue, 18 Sep 2018, Peter Zijlstra wrote:
> On Tue, Sep 18, 2018 at 10:19:09AM +0200, Peter Zijlstra wrote:
> > On Mon, Sep 17, 2018 at 04:29:08PM +0200, Thomas Gleixner wrote:
> > > @@ -1288,23 +1287,23 @@ static int __change_page_attr(struct cpa
> > > err = split_large_page(cpa, kpte, address);
> > > if (!err) {
> > > /*
> > > + * Do a global flush tlb after splitting the large page
> > > + * and before we do the actual change page attribute in the PTE.
> > > + *
> > > + * With out this, we violate the TLB application note, that says
> > > + * "The TLBs may contain both ordinary and large-page
> > > * translations for a 4-KByte range of linear addresses. This
> > > * may occur if software modifies the paging structures so that
> > > * the page size used for the address range changes. If the two
> > > * translations differ with respect to page frame or attributes
> > > * (e.g., permissions), processor behavior is undefined and may
> > > * be implementation-specific."
> > > + *
> > > + * We do this global tlb flush inside the cpa_lock, so that we
> > > * don't allow any other cpu, with stale tlb entries change the
> > > * page attribute in parallel, that also falls into the
> > > * just split large page entry.
> > > + */
> > > flush_tlb_all();
> > > goto repeat;
> > > }
> >
> > this made me look at the tlb invalidation of that thing again; do we
> > want something like the below?
> >
>
> Further cleanups are possible...

Yes please. Can you write up a changelog for that please?

Thanks,

tglx

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