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. Just do nothing if the gpte's permissions are unchanged. Signed-off-by: Lai Jiangshan <jiangshan.ljs@xxxxxxxxxxxx> --- arch/x86/kvm/mmu/paging_tmpl.h | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/arch/x86/kvm/mmu/paging_tmpl.h b/arch/x86/kvm/mmu/paging_tmpl.h index 0ea938276ba8..7db167876cd7 100644 --- a/arch/x86/kvm/mmu/paging_tmpl.h +++ b/arch/x86/kvm/mmu/paging_tmpl.h @@ -1026,6 +1026,11 @@ static int FNAME(sync_spte)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp, int drop_spte(vcpu->kvm, &sp->spt[i]); return 1; } + /* + * Do nothing if the permissions are unchanged. + */ + if (kvm_mmu_page_get_access(sp, i) == pte_access) + return 0; /* Update the shadowed access bits in case they changed. */ kvm_mmu_page_set_access(sp, i, pte_access); -- 2.19.1.6.gb485710b
