[PATCH v2 2/2] x86/hvm: simplify 'mmio_direct' check in epte_get_entry_emt()

[Paul Durrant <paul@xxxxxxx>]

From: Paul Durrant <pdurrant@xxxxxxxxxx>

Re-factor the code to take advantage of the fact that the APIC access page is
a 'special' page.

Suggested-by: Jan Beulich <jbeulich@xxxxxxxx>
Signed-off-by: Paul Durrant <pdurrant@xxxxxxxxxx>
---
Cc: Jan Beulich <jbeulich@xxxxxxxx>
Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Cc: Wei Liu <wl@xxxxxxx>
Cc: "Roger Pau Monné" <roger.pau@xxxxxxxxxx>
---
 xen/arch/x86/hvm/mtrr.c | 15 ++++-----------
 1 file changed, 4 insertions(+), 11 deletions(-)

diff --git a/xen/arch/x86/hvm/mtrr.c b/xen/arch/x86/hvm/mtrr.c
index 3ad813ed15..0992f05e8f 100644
--- a/xen/arch/x86/hvm/mtrr.c
+++ b/xen/arch/x86/hvm/mtrr.c
@@ -814,29 +814,22 @@ int epte_get_entry_emt(struct domain *d, unsigned long 
gfn, mfn_t mfn,
         return -1;
     }
 
-    if ( direct_mmio )
-    {
-        if ( (mfn_x(mfn) ^ mfn_x(d->arch.hvm.vmx.apic_access_mfn)) >> order )
-            return MTRR_TYPE_UNCACHABLE;
-        if ( order )
-            return -1;
-        *ipat = 1;
-        return MTRR_TYPE_WRBACK;
-    }
-
     if ( !mfn_valid(mfn) )
     {
         *ipat = 1;
         return MTRR_TYPE_UNCACHABLE;
     }
 
-    if ( (!is_iommu_enabled(d) && !cache_flush_permitted(d)) ||
+    if ( (!direct_mmio && !is_iommu_enabled(d) && !cache_flush_permitted(d)) ||
          is_special_page(mfn_to_page(mfn)) )
     {
         *ipat = 1;
         return MTRR_TYPE_WRBACK;
     }
 
+    if ( direct_mmio )
+        return MTRR_TYPE_UNCACHABLE;
+
     gmtrr_mtype = hvm_get_mem_pinned_cacheattr(d, _gfn(gfn), order);
     if ( gmtrr_mtype >= 0 )
     {
-- 
2.20.1