[PATCH] KVM: MMU: Let the walker extract the target page gfn from the pte

This fixes a problem where set_pte_common() looked for shadowed pages based on
the page directory gfn (a huge page) instead of the actual gfn being mapped.

Signed-off-by: Avi Kivity <avi@qumranet.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 31 insertions, 17 deletions

diff --git a/drivers/kvm/mmu.c b/drivers/kvm/mmu.c
index ba813f49f8aa..ceae25bfd4b5 100644
--- a/drivers/kvm/mmu.c
+++ b/drivers/kvm/mmu.c
@@ -752,7 +752,8 @@ static inline void set_pte_common(struct kvm_vcpu *vcpu,
                              u64 *shadow_pte,
                              gpa_t gaddr,
                              int dirty,
-                             u64 access_bits)
+                             u64 access_bits,
+                             gfn_t gfn)
 {
         hpa_t paddr;
 
@@ -779,10 +780,10 @@ static inline void set_pte_common(struct kvm_vcpu *vcpu,
         if (access_bits & PT_WRITABLE_MASK) {
                 struct kvm_mmu_page *shadow;
 
-                shadow = kvm_mmu_lookup_page(vcpu, gaddr >> PAGE_SHIFT);
+                shadow = kvm_mmu_lookup_page(vcpu, gfn);
                 if (shadow) {
                         pgprintk("%s: found shadow page for %lx, marking ro\n",
-                                 __FUNCTION__, (gfn_t)(gaddr >> PAGE_SHIFT));
+                                 __FUNCTION__, gfn);
                         access_bits &= ~PT_WRITABLE_MASK;
                         *shadow_pte &= ~PT_WRITABLE_MASK;
                 }
diff --git a/drivers/kvm/paging_tmpl.h b/drivers/kvm/paging_tmpl.h
index cd71973c780c..cf4b74cc75b5 100644
--- a/drivers/kvm/paging_tmpl.h
+++ b/drivers/kvm/paging_tmpl.h
@@ -62,6 +62,7 @@ struct guest_walker {
         pt_element_t *table;
         pt_element_t *ptep;
         pt_element_t inherited_ar;
+        gfn_t gfn;
 };
 
 /*
@@ -113,12 +114,23 @@ static void FNAME(walk_addr)(struct guest_walker *walker,
                 if (is_present_pte(*ptep) && !(*ptep &  PT_ACCESSED_MASK))
                         *ptep |= PT_ACCESSED_MASK;
 
-                if (!is_present_pte(*ptep) ||
-                    walker->level == PT_PAGE_TABLE_LEVEL ||
-                    (walker->level == PT_DIRECTORY_LEVEL &&
-                     (*ptep & PT_PAGE_SIZE_MASK) &&
-                     (PTTYPE == 64 || is_pse(vcpu))))
+                if (!is_present_pte(*ptep))
+                        break;
+
+                if (walker->level == PT_PAGE_TABLE_LEVEL) {
+                        walker->gfn = (*ptep & PT_BASE_ADDR_MASK)
+                                >> PAGE_SHIFT;
+                        break;
+                }
+
+                if (walker->level == PT_DIRECTORY_LEVEL
+                    && (*ptep & PT_PAGE_SIZE_MASK)
+                    && (PTTYPE == 64 || is_pse(vcpu))) {
+                        walker->gfn = (*ptep & PT_DIR_BASE_ADDR_MASK)
+                                >> PAGE_SHIFT;
+                        walker->gfn += PT_INDEX(addr, PT_PAGE_TABLE_LEVEL);
                         break;
+                }
 
                 if (walker->level != 3 || is_long_mode(vcpu))
                         walker->inherited_ar &= walker->table[index];
@@ -143,30 +155,29 @@ static void FNAME(release_walker)(struct guest_walker *walker)
 }
 
 static void FNAME(set_pte)(struct kvm_vcpu *vcpu, u64 guest_pte,
-                           u64 *shadow_pte, u64 access_bits)
+                           u64 *shadow_pte, u64 access_bits, gfn_t gfn)
 {
         ASSERT(*shadow_pte == 0);
         access_bits &= guest_pte;
         *shadow_pte = (guest_pte & PT_PTE_COPY_MASK);
         set_pte_common(vcpu, shadow_pte, guest_pte & PT_BASE_ADDR_MASK,
-                       guest_pte & PT_DIRTY_MASK, access_bits);
+                       guest_pte & PT_DIRTY_MASK, access_bits, gfn);
 }
 
 static void FNAME(set_pde)(struct kvm_vcpu *vcpu, u64 guest_pde,
-                           u64 *shadow_pte, u64 access_bits,
-                           int index)
+                           u64 *shadow_pte, u64 access_bits, gfn_t gfn)
 {
         gpa_t gaddr;
 
         ASSERT(*shadow_pte == 0);
         access_bits &= guest_pde;
-        gaddr = (guest_pde & PT_DIR_BASE_ADDR_MASK) + PAGE_SIZE * index;
+        gaddr = (gpa_t)gfn << PAGE_SHIFT;
         if (PTTYPE == 32 && is_cpuid_PSE36())
                 gaddr |= (guest_pde & PT32_DIR_PSE36_MASK) <<
                         (32 - PT32_DIR_PSE36_SHIFT);
         *shadow_pte = guest_pde & PT_PTE_COPY_MASK;
         set_pte_common(vcpu, shadow_pte, gaddr,
-                       guest_pde & PT_DIRTY_MASK, access_bits);
+                       guest_pde & PT_DIRTY_MASK, access_bits, gfn);
 }
 
 /*
@@ -214,10 +225,12 @@ static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
                                         *prev_shadow_ent |= PT_SHADOW_PS_MARK;
                                 FNAME(set_pde)(vcpu, *guest_ent, shadow_ent,
                                                walker->inherited_ar,
-                                          PT_INDEX(addr, PT_PAGE_TABLE_LEVEL));
+                                               walker->gfn);
                         } else {
                                 ASSERT(walker->level == PT_PAGE_TABLE_LEVEL);
-                                FNAME(set_pte)(vcpu, *guest_ent, shadow_ent, walker->inherited_ar);
+                                FNAME(set_pte)(vcpu, *guest_ent, shadow_ent,
+                                               walker->inherited_ar,
+                                               walker->gfn);
                         }
                         return shadow_ent;
                 }
@@ -291,7 +304,7 @@ static int FNAME(fix_write_pf)(struct kvm_vcpu *vcpu,
                 return 0;
         }
 
-        gfn = (*guest_ent & PT64_BASE_ADDR_MASK) >> PAGE_SHIFT;
+        gfn = walker->gfn;
         if (kvm_mmu_lookup_page(vcpu, gfn)) {
                 pgprintk("%s: found shadow page for %lx, marking ro\n",
                          __FUNCTION__, gfn);