[xen staging] x86/hvm: simplify 'mmio_direct' check in epte_get_entry_emt()

[patchbot@xxxxxxx]

commit 81fd0d3ca4b2cd309403c6e8da662c325dd35750
Author:     Paul Durrant <pdurrant@xxxxxxxxxx>
AuthorDate: Fri Jul 31 17:43:31 2020 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Fri Jul 31 17:43:31 2020 +0200

    x86/hvm: simplify 'mmio_direct' check in epte_get_entry_emt()
    
    Re-factor the code to take advantage of the fact that the APIC access page 
is
    a 'special' page. The VMX code is left alone and hence the APIC access page 
is
    still inserted into the P2M with type p2m_mmio_direct. This is left alone 
as it
    is not obvious there is another suitable type to use, and the necessary
    re-ordering in epte_get_entry_emt() is straightforward.
    
    Suggested-by: Jan Beulich <jbeulich@xxxxxxxx>
    Signed-off-by: Paul Durrant <pdurrant@xxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 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 2bd64e8025..fb051d59c3 100644
--- a/xen/arch/x86/hvm/mtrr.c
+++ b/xen/arch/x86/hvm/mtrr.c
@@ -815,23 +815,13 @@ 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) )
     {
         *ipat = 1;
         return MTRR_TYPE_WRBACK;
@@ -848,6 +838,9 @@ int epte_get_entry_emt(struct domain *d, unsigned long gfn, 
mfn_t mfn,
         }
     }
 
+    if ( direct_mmio )
+        return MTRR_TYPE_UNCACHABLE;
+
     gmtrr_mtype = hvm_get_mem_pinned_cacheattr(d, _gfn(gfn), order);
     if ( gmtrr_mtype >= 0 )
     {
--
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