On Wed, Jul 31, 2024 at 4:27 AM Sean Christopherson <seanjc@xxxxxxxxxx> wrote: > > On Tue, Jul 30, 2024, Paolo Bonzini wrote: > > On 7/30/24 07:32, flyingpenghao@xxxxxxxxx wrote: > > > > > > When tdp_mmu is enabled, invalid root calls kvm_tdp_mmu_zap_invalidated_roots > > > to implement it, and kvm_zap_obsolete_pages is not used. > > > > > > Signed-off-by: Peng Hao<flyingpeng@xxxxxxxxxxx> > > > --- > > > arch/x86/kvm/mmu/mmu.c | 3 ++- > > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > > > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c > > > index 901be9e420a4..e91586c2ef87 100644 > > > --- a/arch/x86/kvm/mmu/mmu.c > > > +++ b/arch/x86/kvm/mmu/mmu.c > > > @@ -6447,7 +6447,8 @@ static void kvm_mmu_zap_all_fast(struct kvm *kvm) > > > */ > > > kvm_make_all_cpus_request(kvm, KVM_REQ_MMU_FREE_OBSOLETE_ROOTS); > > > - kvm_zap_obsolete_pages(kvm); > > > + if (!tdp_mmu_enabled) > > > + kvm_zap_obsolete_pages(kvm); > > > > Can't you have obsolete pages from the shadow MMU that's used for nested > > (nGPA->HPA) virtualization? > > Yep. And kvm_zap_obsolete_pages() is a relatively cheap nop if there are no > pages on active_mmu_pages. E.g. we could check kvm_memslots_have_rmaps(), but I > don't see any point in doing so, as the existing code should be blazing fast > relative to the total cost of the zap. Here can be optimized by judging whether active_mmu_pages is empty, just like kvm_zap_obsolete_pages. Regardless of L0 kvm or L1 kvm, when tdp_mmu is enabled, the active_mmu_pages list will not be used. When ept=0 , the probability that active_mmu_pages is empty is also high, not every time kvm_zap_obsolete_pages is called. Thanks.
