Re: [patch 1/2] x86/mm/pti: Handle unaligned address gracefully in pti_clone_pagetable()

From: Dave Hansen
Date: Wed Aug 28 2019 - 11:46:36 EST

On 8/28/19 7:24 AM, Thomas Gleixner wrote:
> From: Song Liu <songliubraving@xxxxxx>
> 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@xxxxxxxxxxxxxxx>

Song, did you ever root-cause the performance regression? I thought
there were still some mysteries there.