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>

1 files changed, 16 insertions, 2 deletions

diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index 0180ae88307b..9c9e07615139 100644
--- 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;
         }