x86/HVM: correct mtrr_pat_not_equal()

The two vCPU-s differing in MTRR-enabled state means MTRR settings are
not equal. Both vCPU-s having MTRRs disabled means only PAT needs to be
compared. Along those lines for fixed range MTRRs. Differing variable
range counts likewise mean settings are different overall (even if
that's not a very reasonable setup to have).

Constify types and convert bool_t to bool.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>
Release-acked-by: Juergen Gross <jgross@suse.com>

xen/arch/x86/hvm/mtrr.c

@@ -473,35 +473,40 @@ bool_t mtrr_var_range_msr_set(
     return 1;
 }
 
-bool_t mtrr_pat_not_equal(struct vcpu *vd, struct vcpu *vs)
+bool mtrr_pat_not_equal(const struct vcpu *vd, const struct vcpu *vs)
 {
-    struct mtrr_state *md = &vd->arch.hvm_vcpu.mtrr;
-    struct mtrr_state *ms = &vs->arch.hvm_vcpu.mtrr;
-    int32_t res;
-    uint8_t num_var_ranges = (uint8_t)md->mtrr_cap;
+    const struct mtrr_state *md = &vd->arch.hvm_vcpu.mtrr;
+    const struct mtrr_state *ms = &vs->arch.hvm_vcpu.mtrr;
 
-    /* Test fixed ranges. */
-    res = memcmp(md->fixed_ranges, ms->fixed_ranges,
-            NUM_FIXED_RANGES*sizeof(mtrr_type));
-    if ( res )
-        return 1;
+    if ( (md->enabled ^ ms->enabled) & 2 )
+        return true;
 
-    /* Test var ranges. */
-    res = memcmp(md->var_ranges, ms->var_ranges,
-            num_var_ranges*sizeof(struct mtrr_var_range));
-    if ( res )
-        return 1;
+    if ( md->enabled & 2 )
+    {
+        unsigned int num_var_ranges = (uint8_t)md->mtrr_cap;
 
-    /* Test default type MSR. */
-    if ( (md->def_type != ms->def_type)
-            && (md->enabled != ms->enabled) )
-        return 1;
+        /* Test default type MSR. */
+        if ( md->def_type != ms->def_type )
+            return true;
+
+        /* Test fixed ranges. */
+        if ( (md->enabled ^ ms->enabled) & 1 )
+            return true;
+
+        if ( (md->enabled & 1) &&
+             memcmp(md->fixed_ranges, ms->fixed_ranges,
+                    sizeof(md->fixed_ranges)) )
+            return true;
+
+        /* Test variable ranges. */
+        if ( num_var_ranges != (uint8_t)ms->mtrr_cap ||
+             memcmp(md->var_ranges, ms->var_ranges,
+                    num_var_ranges * sizeof(*md->var_ranges)) )
+            return true;
+    }
 
     /* Test PAT. */
-    if ( vd->arch.hvm_vcpu.pat_cr != vs->arch.hvm_vcpu.pat_cr )
-        return 1;
-
-    return 0;
+    return vd->arch.hvm_vcpu.pat_cr != vs->arch.hvm_vcpu.pat_cr;
 }
 
 struct hvm_mem_pinned_cacheattr_range {

xen/include/asm-x86/mtrr.h

@@ -92,6 +92,6 @@ extern void memory_type_changed(struct domain *);
 extern bool_t pat_msr_set(uint64_t *pat, uint64_t msr);
 
 bool_t is_var_mtrr_overlapped(const struct mtrr_state *m);
-bool_t mtrr_pat_not_equal(struct vcpu *vd, struct vcpu *vs);
+bool mtrr_pat_not_equal(const struct vcpu *vd, const struct vcpu *vs);
 
 #endif /* __ASM_X86_MTRR_H__ */