Keep track of accessed/dirty bits; if they are all set, do not
enter the accessed/dirty update loop.
Signed-off-by: Avi Kivity <avi@xxxxxxxxxx>
---
arch/x86/kvm/paging_tmpl.h | 24 ++++++++++++++++++------
1 file changed, 18 insertions(+), 6 deletions(-)
diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
index 95a64d1..5bb3d4f 100644
--- a/arch/x86/kvm/paging_tmpl.h
+++ b/arch/x86/kvm/paging_tmpl.h
@@ -151,7 +151,7 @@ static int FNAME(walk_addr_generic)(struct guest_walker *walker,
pt_element_t pte;
pt_element_t __user *uninitialized_var(ptep_user);
gfn_t table_gfn;
- unsigned index, pt_access, pte_access;
+ unsigned index, pt_access, pte_access, accessed_dirty;
gpa_t pte_gpa;
int offset;
const int write_fault = access & PFERR_WRITE_MASK;
@@ -180,6 +180,7 @@ retry_walk:
ASSERT((!is_long_mode(vcpu) && is_pae(vcpu)) ||
(mmu->get_cr3(vcpu) & CR3_NONPAE_RESERVED_BITS) == 0);
+ accessed_dirty = PT_ACCESSED_MASK;
pt_access = pte_access = ACC_ALL;
++walker->level;
@@ -224,6 +225,7 @@ retry_walk:
goto error;
}
+ accessed_dirty &= pte;
pte_access = pt_access & gpte_access(vcpu, pte);
walker->ptes[walker->level - 1] = pte;
@@ -251,11 +253,21 @@ retry_walk:
if (!write_fault)
protect_clean_gpte(&pte_access, pte);
- ret = FNAME(update_accessed_dirty_bits)(vcpu, mmu, walker, write_fault);
- if (unlikely(ret < 0))
- goto error;
- else if (ret)
- goto retry_walk;
+ /*
+ * On a write fault, fold the dirty bit into accessed_dirty by shifting it one
+ * place right.
+ *
+ * On a read fault, do nothing.
+ */
+ accessed_dirty &= pte >> (write_fault >> ilog2(PFERR_WRITE_MASK));
+
+ if (unlikely(!accessed_dirty)) {
+ ret = FNAME(update_accessed_dirty_bits)(vcpu, mmu, walker, write_fault);
+ if (unlikely(ret < 0))
+ goto error;
+ else if (ret)
+ goto retry_walk;
+ }
walker->pt_access = pt_access;
walker->pte_access = pte_access;
--
1.7.12
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