On Fri, Nov 19, 2010 at 05:05:38PM +0800, Xiao Guangrong wrote: > Quote from Avi: > | I don't think we need to flush immediately; set a "tlb dirty" bit somewhere > | that is cleareded when we flush the tlb. kvm_mmu_notifier_invalidate_page() > | can consult the bit and force a flush if set. > > Signed-off-by: Xiao Guangrong <[email protected]> > --- > arch/x86/kvm/paging_tmpl.h | 4 ++-- > include/linux/kvm_host.h | 7 +++++++ > virt/kvm/kvm_main.c | 8 +++++++- > 3 files changed, 16 insertions(+), 3 deletions(-) > > diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h > index dfb906f..d5c302a 100644 > --- a/arch/x86/kvm/paging_tmpl.h > +++ b/arch/x86/kvm/paging_tmpl.h > @@ -781,14 +781,14 @@ static int FNAME(sync_page)(struct kvm_vcpu *vcpu, > struct kvm_mmu_page *sp) > gfn = gpte_to_gfn(gpte); > > if (FNAME(map_invalid_gpte)(vcpu, sp, &sp->spt[i], gpte)) { > - kvm_flush_remote_tlbs(vcpu->kvm); > + kvm_mark_tlbs_dirty(vcpu->kvm); > continue; > } > > if (gfn != sp->gfns[i]) { > drop_spte(vcpu->kvm, &sp->spt[i], > shadow_trap_nonpresent_pte); > - kvm_flush_remote_tlbs(vcpu->kvm); > + kvm_mark_tlbs_dirty(vcpu->kvm); > continue; > } > > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h > index 4bd663d..82d449b 100644 > --- a/include/linux/kvm_host.h > +++ b/include/linux/kvm_host.h > @@ -249,6 +249,7 @@ struct kvm { > struct mmu_notifier mmu_notifier; > unsigned long mmu_notifier_seq; > long mmu_notifier_count; > + atomic_t tlbs_dirty; > #endif > }; > > @@ -377,6 +378,12 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *vcpu); > void kvm_resched(struct kvm_vcpu *vcpu); > void kvm_load_guest_fpu(struct kvm_vcpu *vcpu); > void kvm_put_guest_fpu(struct kvm_vcpu *vcpu); > + > +static inline void kvm_mark_tlbs_dirty(struct kvm *kvm) > +{ > + atomic_inc(&kvm->tlbs_dirty); > +} > + > void kvm_flush_remote_tlbs(struct kvm *kvm); > void kvm_reload_remote_mmus(struct kvm *kvm); > > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > index fb93ff9..2962569 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -168,8 +168,12 @@ static bool make_all_cpus_request(struct kvm *kvm, > unsigned int req) > > void kvm_flush_remote_tlbs(struct kvm *kvm) > { > + int dirty_count = atomic_read(&kvm->tlbs_dirty); > + > + smp_mb(); > if (make_all_cpus_request(kvm, KVM_REQ_TLB_FLUSH)) > ++kvm->stat.remote_tlb_flush; > + atomic_sub(dirty_count, &kvm->tlbs_dirty); > }
This is racy because kvm_flush_remote_tlbs might be called without mmu_lock protection. You could decrease the counter on invalidate_page/invalidate_range_start only, these are not fast paths anyway. > > void kvm_reload_remote_mmus(struct kvm *kvm) > @@ -249,7 +253,8 @@ static void kvm_mmu_notifier_invalidate_page(struct > mmu_notifier *mn, > idx = srcu_read_lock(&kvm->srcu); > spin_lock(&kvm->mmu_lock); > kvm->mmu_notifier_seq++; > - need_tlb_flush = kvm_unmap_hva(kvm, address); > + need_tlb_flush = kvm_unmap_hva(kvm, address) | > + atomic_read(&kvm->tlbs_dirty); > spin_unlock(&kvm->mmu_lock); > srcu_read_unlock(&kvm->srcu, idx); > > @@ -293,6 +298,7 @@ static void > kvm_mmu_notifier_invalidate_range_start(struct mmu_notifier *mn, > kvm->mmu_notifier_count++; > for (; start < end; start += PAGE_SIZE) > need_tlb_flush |= kvm_unmap_hva(kvm, start); > + need_tlb_flush |= atomic_read(&kvm->tlbs_dirty); > spin_unlock(&kvm->mmu_lock); > srcu_read_unlock(&kvm->srcu, idx); > -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
