xen: don't map missing memory

When setting up a pte for a missing pfn (no matching mfn), just create
an empty pte rather than a junk mapping.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>

1 files changed, 8 insertions, 1 deletions

diff --git a/arch/x86/include/asm/xen/page.h b/arch/x86/include/asm/xen/page.h
index e40ca6e67bb5..875f5a08a6c7 100644
--- a/arch/x86/include/asm/xen/page.h
+++ b/arch/x86/include/asm/xen/page.h
@@ -41,10 +41,17 @@ extern bool set_phys_to_machine(unsigned long pfn, unsigned long mfn);
 
 static inline unsigned long pfn_to_mfn(unsigned long pfn)
 {
+        unsigned long mfn;
+
         if (xen_feature(XENFEAT_auto_translated_physmap))
                 return pfn;
 
-        return get_phys_to_machine(pfn) & ~FOREIGN_FRAME_BIT;
+        mfn = get_phys_to_machine(pfn);
+
+        if (mfn != INVALID_P2M_ENTRY)
+                mfn &= ~FOREIGN_FRAME_BIT;
+
+        return mfn;
 }
 
 static inline int phys_to_machine_mapping_valid(unsigned long pfn)