KVM: MTRR: fix memory type handling if MTRR is completely disabled

Currently code uses default memory type if MTRR is fully disabled,
fix it by using UC instead.

Signed-off-by: Xiao Guangrong <guangrong.xiao@intel.com>
Tested-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 20 insertions, 1 deletions

diff --git a/arch/x86/kvm/mtrr.c b/arch/x86/kvm/mtrr.c
index de1d2d8062e2..e2750134a22b 100644
--- a/arch/x86/kvm/mtrr.c
+++ b/arch/x86/kvm/mtrr.c
@@ -120,6 +120,16 @@ static u8 mtrr_default_type(struct kvm_mtrr *mtrr_state)
         return mtrr_state->deftype & IA32_MTRR_DEF_TYPE_TYPE_MASK;
 }
 
+static u8 mtrr_disabled_type(void)
+{
+        /*
+         * Intel SDM 11.11.2.2: all MTRRs are disabled when
+         * IA32_MTRR_DEF_TYPE.E bit is cleared, and the UC
+         * memory type is applied to all of physical memory.
+         */
+        return MTRR_TYPE_UNCACHABLE;
+}
+
 /*
 * Three terms are used in the following code:
 * - segment, it indicates the address segments covered by fixed MTRRs.
@@ -434,6 +444,8 @@ struct mtrr_iter {
 
         /* output fields. */
         int mem_type;
+        /* mtrr is completely disabled? */
+        bool mtrr_disabled;
         /* [start, end) is not fully covered in MTRRs? */
         bool partial_map;
 
@@ -549,7 +561,7 @@ static void mtrr_lookup_var_next(struct mtrr_iter *iter)
 static void mtrr_lookup_start(struct mtrr_iter *iter)
 {
         if (!mtrr_is_enabled(iter->mtrr_state)) {
-                iter->partial_map = true;
+                iter->mtrr_disabled = true;
                 return;
         }
 
@@ -563,6 +575,7 @@ static void mtrr_lookup_init(struct mtrr_iter *iter,
         iter->mtrr_state = mtrr_state;
         iter->start = start;
         iter->end = end;
+        iter->mtrr_disabled = false;
         iter->partial_map = false;
         iter->fixed = false;
         iter->range = NULL;
@@ -656,6 +669,9 @@ u8 kvm_mtrr_get_guest_memory_type(struct kvm_vcpu *vcpu, gfn_t gfn)
                 return MTRR_TYPE_WRBACK;
         }
 
+        if (iter.mtrr_disabled)
+                return mtrr_disabled_type();
+
         /* It is not covered by MTRRs. */
         if (iter.partial_map) {
                 /*
@@ -689,6 +705,9 @@ bool kvm_mtrr_check_gfn_range_consistency(struct kvm_vcpu *vcpu, gfn_t gfn,
                         return false;
         }
 
+        if (iter.mtrr_disabled)
+                return true;
+
         if (!iter.partial_map)
                 return true;