KVM: MMU: fix dirty bit setting when removing write permissions

When mmu_set_spte() checks if a page related to spte should be release as
dirty or clean, it check if the shadow pte was writeble, but in case
rmap_write_protect() is called called it is possible for shadow ptes that were
writeble to become readonly and therefor mmu_set_spte will release the pages
as clean.

This patch fix this issue by marking the page as dirty inside
rmap_write_protect().

Signed-off-by: Izik Eidus <izike@qumranet.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>

1 files changed, 8 insertions, 0 deletions

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index a5872b3c466d..dd4b95b3896b 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -626,6 +626,14 @@ static void rmap_write_protect(struct kvm *kvm, u64 gfn)
                 }
                 spte = rmap_next(kvm, rmapp, spte);
         }
+        if (write_protected) {
+                struct page *page;
+
+                spte = rmap_next(kvm, rmapp, NULL);
+                page = pfn_to_page((*spte & PT64_BASE_ADDR_MASK) >> PAGE_SHIFT);
+                SetPageDirty(page);
+        }
+
         /* check for huge page mappings */
         rmapp = gfn_to_rmap(kvm, gfn, 1);
         spte = rmap_next(kvm, rmapp, NULL);