Re: [PATCH 1/2] kvm: x86/mmu: Reduce the update to the spte in FNAME(sync_page)

[Lai Jiangshan]

On Wed, Dec 14, 2022 at 2:12 AM Sean Christopherson <seanjc@xxxxxxxxxx> wrote:
>
> On Mon, Dec 12, 2022, Lai Jiangshan wrote:
> > From: Lai Jiangshan <jiangshan.ljs@xxxxxxxxxxxx>
> >
> > Sometimes when the guest updates its pagetable, it adds only new gptes
> > to it without changing any existed one, so there is no point to update
> > the sptes for these existed gptes.
> >
> > Also when the sptes for these unchanged gptes are updated, the AD
> > bits are also removed since make_spte() is called with prefetch=true
> > which might result unneeded TLB flushing.
>
> If either of the proposed changes is kept, please move this to a separate patch.
> Skipping updates for PTEs with the same protections is separate logical change
> from skipping updates when making the SPTE writable.
>

Did as you suggested:
https://lore.kernel.org/lkml/20230105095848.6061-5-jiangshanlai@xxxxxxxxx/