Re: [PATCH v2 6/6] KVM: x86/mmu: Use 1 as the size of gfn range for tlb flushing in FNAME(invlpg)()

Hou Wenlong
2022-09-13T12:59:06Z

On Thu, Sep 08, 2022 at 01:40:16AM +0800, David Matlack wrote:
> On Wed, Aug 24, 2022 at 05:29:23PM +0800, Hou Wenlong wrote:
> > Only SP with PG_LEVLE_4K level could be unsync, so the size of gfn range
> > must be 1.
> >
> > Signed-off-by: Hou Wenlong <houwenlong.hwl@antgroup.com>
> > ---
> > arch/x86/kvm/mmu/paging_tmpl.h | 3 ++-
> > 1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/x86/kvm/mmu/paging_tmpl.h b/arch/x86/kvm/mmu/paging_tmpl.h
> > index 04149c704d5b..486a3163b1e4 100644
> > --- a/arch/x86/kvm/mmu/paging_tmpl.h
> > +++ b/arch/x86/kvm/mmu/paging_tmpl.h
> > @@ -937,7 +937,8 @@ static void FNAME(invlpg)(struct kvm_vcpu *vcpu, gva_t gva, hpa_t root_hpa)
> >
> > mmu_page_zap_pte(vcpu->kvm, sp, sptep, NULL);
> > if (is_shadow_present_pte(old_spte))
> > - kvm_flush_remote_tlbs_sptep(vcpu->kvm, sptep);
> > + kvm_flush_remote_tlbs_gfn(vcpu->kvm,
> > + kvm_mmu_page_get_gfn(sp, sptep - sp->spt), 1);
>
> The third argument to kvm_flush_remote_tlbs_gfn() is the level, not the
> number of pages. But that aside, I don't understand why this patch is
> necessary. kvm_flush_remote_tlbs_sptep() should already do the right
> thing.
>
Since only SP with PG_LEVEL_4K level could be unsync, so the level must
be PG_LEVEL_4K, then sp->role.level access could be dropped. However,
I'm not sure whether it is useful. I can drop it if it is useless.

> >
> > if (!rmap_can_add(vcpu))
> > break;
> > --
> > 2.31.1
> >