1 files changed, 34 insertions, 2 deletions

diff --git a/drivers/kvm/paging_tmpl.h b/drivers/kvm/paging_tmpl.h
index 3c40a598ceb8..8086f827120f 100644
--- a/drivers/kvm/paging_tmpl.h
+++ b/drivers/kvm/paging_tmpl.h
@@ -34,7 +34,9 @@
         #define PT_LEVEL_BITS PT64_LEVEL_BITS
         #ifdef CONFIG_X86_64
         #define PT_MAX_FULL_LEVELS 4
+        #define CMPXCHG cmpxchg
         #else
+        #define CMPXCHG cmpxchg64
         #define PT_MAX_FULL_LEVELS 2
         #endif
 #elif PTTYPE == 32
@@ -48,6 +50,7 @@
         #define PT_LEVEL_MASK(level) PT32_LEVEL_MASK(level)
         #define PT_LEVEL_BITS PT32_LEVEL_BITS
         #define PT_MAX_FULL_LEVELS 2
+        #define CMPXCHG cmpxchg
 #else
         #error Invalid PTTYPE value
 #endif
@@ -78,6 +81,26 @@ static gfn_t gpte_to_gfn_pde(pt_element_t gpte)
         return (gpte & PT_DIR_BASE_ADDR_MASK) >> PAGE_SHIFT;
 }
 
+static bool FNAME(cmpxchg_gpte)(struct kvm *kvm,
+                         gfn_t table_gfn, unsigned index,
+                         pt_element_t orig_pte, pt_element_t new_pte)
+{
+        pt_element_t ret;
+        pt_element_t *table;
+        struct page *page;
+
+        page = gfn_to_page(kvm, table_gfn);
+        table = kmap_atomic(page, KM_USER0);
+
+        ret = CMPXCHG(&table[index], orig_pte, new_pte);
+
+        kunmap_atomic(table, KM_USER0);
+
+        kvm_release_page_dirty(page);
+
+        return (ret != orig_pte);
+}
+
 /*
  * Fetch a guest pte for a guest virtual address
  */
@@ -91,6 +114,7 @@ static int FNAME(walk_addr)(struct guest_walker *walker,
         gpa_t pte_gpa;
 
         pgprintk("%s: addr %lx\n", __FUNCTION__, addr);
+walk:
         walker->level = vcpu->mmu.root_level;
         pte = vcpu->cr3;
 #if PTTYPE == 64
@@ -135,8 +159,10 @@ static int FNAME(walk_addr)(struct guest_walker *walker,
 
                 if (!(pte & PT_ACCESSED_MASK)) {
                         mark_page_dirty(vcpu->kvm, table_gfn);
+                        if (FNAME(cmpxchg_gpte)(vcpu->kvm, table_gfn,
+                            index, pte, pte|PT_ACCESSED_MASK))
+                                goto walk;
                         pte |= PT_ACCESSED_MASK;
-                        kvm_write_guest(vcpu->kvm, pte_gpa, &pte, sizeof(pte));
                 }
 
                 if (walker->level == PT_PAGE_TABLE_LEVEL) {
@@ -159,9 +185,14 @@ static int FNAME(walk_addr)(struct guest_walker *walker,
         }
 
         if (write_fault && !is_dirty_pte(pte)) {
+                bool ret;
+
                 mark_page_dirty(vcpu->kvm, table_gfn);
+                ret = FNAME(cmpxchg_gpte)(vcpu->kvm, table_gfn, index, pte,
+                            pte|PT_DIRTY_MASK);
+                if (ret)
+                        goto walk;
                 pte |= PT_DIRTY_MASK;
-                kvm_write_guest(vcpu->kvm, pte_gpa, &pte, sizeof(pte));
                 kvm_mmu_pte_write(vcpu, pte_gpa, (u8 *)&pte, sizeof(pte));
         }
 
@@ -484,3 +515,4 @@ static void FNAME(prefetch_page)(struct kvm_vcpu *vcpu,
 #undef PT_MAX_FULL_LEVELS
 #undef gpte_to_gfn
 #undef gpte_to_gfn_pde
+#undef CMPXCHG