KVM: MMU: Disable write access on clean large pages
By forcing clean huge pages to be read-only, we have separate roles
for the shadow of a clean large page and the shadow of a dirty large
page. This is necessary because different ptes will be instantiated
for the two cases, even for read faults.
Signed-off-by: Avi Kivity <avi@qumranet.com>
diff --git a/drivers/kvm/paging_tmpl.h b/drivers/kvm/paging_tmpl.h
index e07cb2e..4538b15 100644
--- a/drivers/kvm/paging_tmpl.h
+++ b/drivers/kvm/paging_tmpl.h
@@ -382,6 +382,8 @@
metaphysical = 1;
hugepage_access = walker->pte;
hugepage_access &= PT_USER_MASK | PT_WRITABLE_MASK;
+ if (!is_dirty_pte(walker->pte))
+ hugepage_access &= ~PT_WRITABLE_MASK;
hugepage_access >>= PT_WRITABLE_SHIFT;
if (walker->pte & PT64_NX_MASK)
hugepage_access |= (1 << 2);