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>

diff --git a/arch/x86/include/asm/xen/page.h b/arch/x86/include/asm/xen/page.h
index e40ca6e67bb5b7653e18ec6eba1ed629e280770c..875f5a08a6c788e1471ad188dd2cf9e34a2f76af 100644 (file)
--- 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)

diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index 9b43bb398d377b2fef4b432f1d63be30fb9f0957..4c63b7f452dd08d33dec3db12d7d851dcbb1321d 100644 (file)
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -745,7 +745,20 @@ 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;
-               val = ((pteval_t)pfn_to_mfn(pfn) << PAGE_SHIFT) | flags;
+               unsigned long mfn = pfn_to_mfn(pfn);
+
+               /*
+                * If there's no mfn for the pfn, then just create an
+                * empty non-present pte.  Unfortunately this loses
+                * information about the original pfn, so
+                * pte_mfn_to_pfn is asymmetric.
+                */
+               if (unlikely(mfn == INVALID_P2M_ENTRY)) {
+                       mfn = 0;
+                       flags = 0;
+               }
+
+               val = ((pteval_t)mfn << PAGE_SHIFT) | flags;
        }
 
        return val;