KVM: Simplify kvm->tlbs_dirty handling
When this was introduced, kvm_flush_remote_tlbs() could be called
without holding mmu_lock. It is now acknowledged that the function
must be called before releasing mmu_lock, and all callers have already
been changed to do so.
There is no need to use smp_mb() and cmpxchg() any more.
Signed-off-by: Takuya Yoshikawa <yoshikawa_takuya_b1@lab.ntt.co.jp>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
index cba218a..b1e6c1b 100644
--- a/arch/x86/kvm/paging_tmpl.h
+++ b/arch/x86/kvm/paging_tmpl.h
@@ -913,7 +913,8 @@
* 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.
+ * We set tlbs_dirty to let the notifier know this change and delay the flush
+ * until such a case actually happens.
*/
static int FNAME(sync_page)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp)
{
@@ -942,7 +943,7 @@
return -EINVAL;
if (FNAME(prefetch_invalid_gpte)(vcpu, sp, &sp->spt[i], gpte)) {
- vcpu->kvm->tlbs_dirty++;
+ vcpu->kvm->tlbs_dirty = true;
continue;
}
@@ -957,7 +958,7 @@
if (gfn != sp->gfns[i]) {
drop_spte(vcpu->kvm, &sp->spt[i]);
- vcpu->kvm->tlbs_dirty++;
+ vcpu->kvm->tlbs_dirty = true;
continue;
}
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index f5937b8..9816b68 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -401,7 +401,9 @@
unsigned long mmu_notifier_seq;
long mmu_notifier_count;
#endif
- long tlbs_dirty;
+ /* Protected by mmu_lock */
+ bool tlbs_dirty;
+
struct list_head devices;
};
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index a9e999a..f5668a4 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -186,12 +186,9 @@
void kvm_flush_remote_tlbs(struct kvm *kvm)
{
- long 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);
+ kvm->tlbs_dirty = false;
}
EXPORT_SYMBOL_GPL(kvm_flush_remote_tlbs);