On Mon, Nov 01, 2021, Junaid Shahid wrote: > The fast page fault path bails out on write faults to huge pages in > order to accommodate dirty logging. This change adds a check to do that > only when dirty logging is actually enabled, so that access tracking for > huge pages can still use the fast path for write faults in the common > case. > > Signed-off-by: Junaid Shahid <junaids@xxxxxxxxxx> One nit, otherwise Reviewed-by: Sean Christopherson <seanjc@xxxxxxxxxx> > --- > arch/x86/kvm/mmu/mmu.c | 8 +++++--- > 1 file changed, 5 insertions(+), 3 deletions(-) > > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c > index 354d2ca92df4..5df9181c5082 100644 > --- a/arch/x86/kvm/mmu/mmu.c > +++ b/arch/x86/kvm/mmu/mmu.c > @@ -3191,8 +3191,9 @@ static int fast_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault) > new_spte |= PT_WRITABLE_MASK; > > /* > - * Do not fix write-permission on the large spte. Since > - * we only dirty the first page into the dirty-bitmap in > + * Do not fix write-permission on the large spte when > + * dirty logging is enabled. Since we only dirty the > + * first page into the dirty-bitmap in > * fast_pf_fix_direct_spte(), other pages are missed > * if its slot has dirty logging enabled. > * > @@ -3201,7 +3202,8 @@ static int fast_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault) > * > * See the comments in kvm_arch_commit_memory_region(). This part is slightly stale as kvm_mmu_slot_apply_flags() now has the comments. Maybe just drop it entirely? The comments there don't do a whole lot to make this code more understandable. > */ > - if (sp->role.level > PG_LEVEL_4K) > + if (sp->role.level > PG_LEVEL_4K && > + kvm_slot_dirty_track_enabled(fault->slot)) > break; > } > > -- > 2.33.1.1089.g2158813163f-goog >
