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authorXiao Guangrong <xiaoguangrong@cn.fujitsu.com>2010-11-23 11:13:00 +0800
committerAvi Kivity <avi@redhat.com>2011-01-12 11:29:51 +0200
commita4ee1ca4a36e7857d90ae8c2b85f1bde9a042c10 (patch)
tree29707dd004ef14df318ac35321b95ac62570fc99
parent407c61c6bd6a51b56d02f8bbad8aadf19db8c7b5 (diff)
KVM: MMU: delay flush all tlbs on sync_page path
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 <xiaoguangrong@cn.fujitsu.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
-rw-r--r--arch/x86/kvm/paging_tmpl.h12
-rw-r--r--include/linux/kvm_host.h2
-rw-r--r--virt/kvm/kvm_main.c7
3 files changed, 18 insertions, 3 deletions
diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
index a43f4ccd30b..2b3d66c7b68 100644
--- a/arch/x86/kvm/paging_tmpl.h
+++ b/arch/x86/kvm/paging_tmpl.h
@@ -746,6 +746,14 @@ static void FNAME(prefetch_page)(struct kvm_vcpu *vcpu,
* Using the cached information from sp->gfns is safe because:
* - The spte has a reference to the struct page, so the pfn for a given gfn
* can't change unless all sptes pointing to it are nuked first.
+ *
+ * Note:
+ * We should flush all tlbs if spte is dropped even though guest is
+ * responsible for it. Since if we don't, kvm_mmu_notifier_invalidate_page
+ * and kvm_mmu_notifier_invalidate_range_start detect the mapping page isn't
+ * used by guest then tlbs are not flushed, so guest is allowed to access the
+ * freed pages.
+ * And we increase kvm->tlbs_dirty to delay tlbs flush in this case.
*/
static int FNAME(sync_page)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp)
{
@@ -781,14 +789,14 @@ static int FNAME(sync_page)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp)
gfn = gpte_to_gfn(gpte);
if (FNAME(prefetch_invalid_gpte)(vcpu, sp, &sp->spt[i], gpte)) {
- kvm_flush_remote_tlbs(vcpu->kvm);
+ vcpu->kvm->tlbs_dirty++;
continue;
}
if (gfn != sp->gfns[i]) {
drop_spte(vcpu->kvm, &sp->spt[i],
shadow_trap_nonpresent_pte);
- kvm_flush_remote_tlbs(vcpu->kvm);
+ vcpu->kvm->tlbs_dirty++;
continue;
}
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index da0794f707f..ac4e83a1a10 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -254,6 +254,7 @@ struct kvm {
struct mmu_notifier mmu_notifier;
unsigned long mmu_notifier_seq;
long mmu_notifier_count;
+ long tlbs_dirty;
#endif
};
@@ -382,6 +383,7 @@ 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);
+
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 5156d458a84..ee99b77e445 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 = kvm->tlbs_dirty;
+
+ smp_mb();
if (make_all_cpus_request(kvm, KVM_REQ_TLB_FLUSH))
++kvm->stat.remote_tlb_flush;
+ cmpxchg(&kvm->tlbs_dirty, dirty_count, 0);
}
void kvm_reload_remote_mmus(struct kvm *kvm)
@@ -249,7 +253,7 @@ 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) | kvm->tlbs_dirty;
spin_unlock(&kvm->mmu_lock);
srcu_read_unlock(&kvm->srcu, idx);
@@ -293,6 +297,7 @@ 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 |= kvm->tlbs_dirty;
spin_unlock(&kvm->mmu_lock);
srcu_read_unlock(&kvm->srcu, idx);