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SubjectRe: [patch 1/2] x86/mm/pti: Handle unaligned address gracefully in pti_clone_pagetable()
On Wed, 28 Aug 2019, Dave Hansen wrote:
> On 8/28/19 7:24 AM, Thomas Gleixner wrote:
> > From: Song Liu <songliubraving@fb.com>
> >
> > pti_clone_pmds() assumes that the supplied address is either:
> >
> > - properly PUD/PMD aligned
> > or
> > - the address is actually mapped which means that independent
> > of the mapping level (PUD/PMD/PTE) the next higher mapping
> > exist.
> >
> > If that's not the case the unaligned address can be incremented by PUD or
> > PMD size wrongly. All callers supply mapped and/or aligned addresses, but
> > for robustness sake, it's better to handle that case proper and to emit a
> > warning.
>
> Reviewed-by: Dave Hansen <dave.hansen@linux.intel.com>
>
> Song, did you ever root-cause the performance regression? I thought
> there were still some mysteries there.

See Peter's series to rework the ftrace code patching ...

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