[PATCH 4/5] KVM: MMU: Ignore pcd, pwt, and pat bits on ptes

[Avi Kivity <avi@qumranet.com>]

The pcd, pwt, and pat bits on page table entries affect the cpu cache.  Since
the cache is a host resource, the guest should not be able to control it.
Moreover, the meaning of these bits changes depending on whether pat is
enabled or not.

So, force these bits to zero on shadow page table entries at all times.

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

Index: linux-2.6/drivers/kvm/mmu.c
===================================================================
--- linux-2.6.orig/drivers/kvm/mmu.c
+++ linux-2.6/drivers/kvm/mmu.c
@@ -61,22 +61,9 @@
 
 
 #define PT32_PTE_COPY_MASK \
-	(PT_PRESENT_MASK | PT_PWT_MASK | PT_PCD_MASK | \
-	PT_ACCESSED_MASK | PT_DIRTY_MASK | PT_PAT_MASK | \
-	PT_GLOBAL_MASK )
-
-#define PT32_NON_PTE_COPY_MASK \
-	(PT_PRESENT_MASK | PT_PWT_MASK | PT_PCD_MASK | \
-	PT_ACCESSED_MASK | PT_DIRTY_MASK)
-
-
-#define PT64_PTE_COPY_MASK \
-	(PT64_NX_MASK | PT32_PTE_COPY_MASK)
-
-#define PT64_NON_PTE_COPY_MASK \
-	(PT64_NX_MASK | PT32_NON_PTE_COPY_MASK)
-
+	(PT_PRESENT_MASK | PT_ACCESSED_MASK | PT_DIRTY_MASK | PT_GLOBAL_MASK)
 
+#define PT64_PTE_COPY_MASK (PT64_NX_MASK | PT32_PTE_COPY_MASK)
 
 #define PT_FIRST_AVAIL_BITS_SHIFT 9
 #define PT64_SECOND_AVAIL_BITS_SHIFT 52
Index: linux-2.6/drivers/kvm/paging_tmpl.h
===================================================================
--- linux-2.6.orig/drivers/kvm/paging_tmpl.h
+++ linux-2.6/drivers/kvm/paging_tmpl.h
@@ -32,7 +32,6 @@
 	#define SHADOW_PT_INDEX(addr, level) PT64_INDEX(addr, level)
 	#define PT_LEVEL_MASK(level) PT64_LEVEL_MASK(level)
 	#define PT_PTE_COPY_MASK PT64_PTE_COPY_MASK
-	#define PT_NON_PTE_COPY_MASK PT64_NON_PTE_COPY_MASK
 #elif PTTYPE == 32
 	#define pt_element_t u32
 	#define guest_walker guest_walker32
@@ -43,7 +42,6 @@
 	#define SHADOW_PT_INDEX(addr, level) PT64_INDEX(addr, level)
 	#define PT_LEVEL_MASK(level) PT32_LEVEL_MASK(level)
 	#define PT_PTE_COPY_MASK PT32_PTE_COPY_MASK
-	#define PT_NON_PTE_COPY_MASK PT32_NON_PTE_COPY_MASK
 #else
 	#error Invalid PTTYPE value
 #endif
@@ -105,9 +103,7 @@ static void FNAME(set_pde)(struct kvm_vc
 	if (PTTYPE == 32 && is_cpuid_PSE36())
 		gaddr |= (guest_pde & PT32_DIR_PSE36_MASK) <<
 			(32 - PT32_DIR_PSE36_SHIFT);
-	*shadow_pte = (guest_pde & (PT_NON_PTE_COPY_MASK | PT_GLOBAL_MASK)) |
-		          ((guest_pde & PT_DIR_PAT_MASK) >>
-			            (PT_DIR_PAT_SHIFT - PT_PAT_SHIFT));
+	*shadow_pte = guest_pde & PT_PTE_COPY_MASK;
 	set_pte_common(vcpu, shadow_pte, gaddr,
 		       guest_pde & PT_DIRTY_MASK, access_bits);
 }
@@ -162,6 +158,7 @@ static u64 *FNAME(fetch)(struct kvm_vcpu
 		u32 index = SHADOW_PT_INDEX(addr, level);
 		u64 *shadow_ent = ((u64 *)__va(shadow_addr)) + index;
 		pt_element_t *guest_ent;
+		u64 shadow_pte;
 
 		if (is_present_pte(*shadow_ent) || is_io_pte(*shadow_ent)) {
 			if (level == PT_PAGE_TABLE_LEVEL)
@@ -204,14 +201,11 @@ static u64 *FNAME(fetch)(struct kvm_vcpu
 		shadow_addr = kvm_mmu_alloc_page(vcpu, shadow_ent);
 		if (!VALID_PAGE(shadow_addr))
 			return ERR_PTR(-ENOMEM);
-		if (!kvm_arch_ops->is_long_mode(vcpu) && level == 3)
-			*shadow_ent = shadow_addr |
-				(*guest_ent & (PT_PRESENT_MASK | PT_PWT_MASK | PT_PCD_MASK));
-		else {
-			*shadow_ent = shadow_addr |
-				(*guest_ent & PT_NON_PTE_COPY_MASK);
-			*shadow_ent |= (PT_WRITABLE_MASK | PT_USER_MASK);
-		}
+		shadow_pte = shadow_addr | PT_PRESENT_MASK;
+		if (vcpu->mmu.root_level > 3 || level != 3)
+			shadow_pte |= PT_ACCESSED_MASK
+				| PT_WRITABLE_MASK | PT_USER_MASK;
+		*shadow_ent = shadow_pte;
 		prev_shadow_ent = shadow_ent;
 	}
 }