xen/mmu: Set _PAGE_IOMAP if PFN is an identity PFN.

If we find that the PFN is within the P2M as an identity
PFN make sure to tack on the _PAGE_IOMAP flag.

Reviewed-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index 0180ae8..9c9e076 100644 (file)
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -416,8 +416,12 @@ static pteval_t pte_pfn_to_mfn(pteval_t val)
        if (val & _PAGE_PRESENT) {
                unsigned long pfn = (val & PTE_PFN_MASK) >> PAGE_SHIFT;
                pteval_t flags = val & PTE_FLAGS_MASK;
-               unsigned long mfn = pfn_to_mfn(pfn);
+               unsigned long mfn;
 
+               if (!xen_feature(XENFEAT_auto_translated_physmap))
+                       mfn = get_phys_to_machine(pfn);
+               else
+                       mfn = pfn;
                /*
                 * If there's no mfn for the pfn, then just create an
                 * empty non-present pte.  Unfortunately this loses
@@ -427,8 +431,18 @@ static pteval_t pte_pfn_to_mfn(pteval_t val)
                if (unlikely(mfn == INVALID_P2M_ENTRY)) {
                        mfn = 0;
                        flags = 0;
+               } else {
+                       /*
+                        * Paramount to do this test _after_ the
+                        * INVALID_P2M_ENTRY as INVALID_P2M_ENTRY &
+                        * IDENTITY_FRAME_BIT resolves to true.
+                        */
+                       mfn &= ~FOREIGN_FRAME_BIT;
+                       if (mfn & IDENTITY_FRAME_BIT) {
+                               mfn &= ~IDENTITY_FRAME_BIT;
+                               flags |= _PAGE_IOMAP;
+                       }
                }
-
                val = ((pteval_t)mfn << PAGE_SHIFT) | flags;
        }