KVM: MMU: mark page dirty only when page is really written
Mark page dirty only when this page is really written, it's more exacter,
and also can fix dirty page marking in speculation path
Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index c07b9a2..ff95d41 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -307,24 +307,42 @@
if (!is_shadow_present_pte(spte))
return false;
- if (spte & shadow_accessed_mask)
+ if ((spte & shadow_accessed_mask) &&
+ (!is_writable_pte(spte) || (spte & shadow_dirty_mask)))
return false;
return true;
}
+static bool spte_is_bit_cleared(u64 old_spte, u64 new_spte, u64 bit_mask)
+{
+ return (old_spte & bit_mask) && !(new_spte & bit_mask);
+}
+
static void update_spte(u64 *sptep, u64 new_spte)
{
- u64 old_spte;
+ u64 mask, old_spte = *sptep;
- if (!shadow_accessed_mask || (new_spte & shadow_accessed_mask) ||
- !is_rmap_spte(*sptep))
+ WARN_ON(!is_rmap_spte(new_spte));
+
+ new_spte |= old_spte & shadow_dirty_mask;
+
+ mask = shadow_accessed_mask;
+ if (is_writable_pte(old_spte))
+ mask |= shadow_dirty_mask;
+
+ if (!spte_has_volatile_bits(old_spte) || (new_spte & mask) == mask)
__set_spte(sptep, new_spte);
- else {
+ else
old_spte = __xchg_spte(sptep, new_spte);
- if (old_spte & shadow_accessed_mask)
- kvm_set_pfn_accessed(spte_to_pfn(old_spte));
- }
+
+ if (!shadow_accessed_mask)
+ return;
+
+ if (spte_is_bit_cleared(old_spte, new_spte, shadow_accessed_mask))
+ kvm_set_pfn_accessed(spte_to_pfn(old_spte));
+ if (spte_is_bit_cleared(old_spte, new_spte, shadow_dirty_mask))
+ kvm_set_pfn_dirty(spte_to_pfn(old_spte));
}
static int mmu_topup_memory_cache(struct kvm_mmu_memory_cache *cache,
@@ -704,7 +722,7 @@
pfn = spte_to_pfn(old_spte);
if (!shadow_accessed_mask || old_spte & shadow_accessed_mask)
kvm_set_pfn_accessed(pfn);
- if (is_writable_pte(old_spte))
+ if (!shadow_dirty_mask || (old_spte & shadow_dirty_mask))
kvm_set_pfn_dirty(pfn);
}
@@ -759,13 +777,6 @@
}
spte = rmap_next(kvm, rmapp, spte);
}
- if (write_protected) {
- pfn_t pfn;
-
- spte = rmap_next(kvm, rmapp, NULL);
- pfn = spte_to_pfn(*spte);
- kvm_set_pfn_dirty(pfn);
- }
/* check for huge page mappings */
for (i = PT_DIRECTORY_LEVEL;
@@ -1938,7 +1949,7 @@
* whether the guest actually used the pte (in order to detect
* demand paging).
*/
- spte = shadow_base_present_pte | shadow_dirty_mask;
+ spte = shadow_base_present_pte;
if (!speculative)
spte |= shadow_accessed_mask;
if (!dirty)
@@ -1999,8 +2010,6 @@
mark_page_dirty(vcpu->kvm, gfn);
set_pte:
- if (is_writable_pte(*sptep) && !is_writable_pte(spte))
- kvm_set_pfn_dirty(pfn);
update_spte(sptep, spte);
done:
return ret;