KVM: MMU: flush tlb out of mmu lock when write-protect the sptes
Now we can flush all the TLBs out of the mmu lock without TLB corruption when
write-proect the sptes, it is because:
- we have marked large sptes readonly instead of dropping them that means we
just change the spte from writable to readonly so that we only need to care
the case of changing spte from present to present (changing the spte from
present to nonpresent will flush all the TLBs immediately), in other words,
the only case we need to care is mmu_spte_update()
- in mmu_spte_update(), we haved checked
SPTE_HOST_WRITEABLE | PTE_MMU_WRITEABLE instead of PT_WRITABLE_MASK, that
means it does not depend on PT_WRITABLE_MASK anymore
Acked-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 63a828d..c5582c3 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3632,11 +3632,19 @@
offset = i * BITS_PER_LONG;
kvm_mmu_write_protect_pt_masked(kvm, memslot, offset, mask);
}
- if (is_dirty)
- kvm_flush_remote_tlbs(kvm);
spin_unlock(&kvm->mmu_lock);
+ /* See the comments in kvm_mmu_slot_remove_write_access(). */
+ lockdep_assert_held(&kvm->slots_lock);
+
+ /*
+ * All the TLBs can be flushed out of mmu lock, see the comments in
+ * kvm_mmu_slot_remove_write_access().
+ */
+ if (is_dirty)
+ kvm_flush_remote_tlbs(kvm);
+
r = -EFAULT;
if (copy_to_user(log->dirty_bitmap, dirty_bitmap_buffer, n))
goto out;