1 files changed, 14 insertions, 4 deletions

diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index d4d52f5a1cf7..aba77b2b7d18 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -246,11 +246,21 @@ xmaddr_t arbitrary_virt_to_machine(void *vaddr)
 {
         unsigned long address = (unsigned long)vaddr;
         unsigned int level;
-        pte_t *pte = lookup_address(address, &level);
-        unsigned offset = address & ~PAGE_MASK;
+        pte_t *pte;
+        unsigned offset;
 
-        BUG_ON(pte == NULL);
+        /*
+         * if the PFN is in the linear mapped vaddr range, we can just use
+         * the (quick) virt_to_machine() p2m lookup
+         */
+        if (virt_addr_valid(vaddr))
+                return virt_to_machine(vaddr);
 
+        /* otherwise we have to do a (slower) full page-table walk */
+
+        pte = lookup_address(address, &level);
+        BUG_ON(pte == NULL);
+        offset = address & ~PAGE_MASK;
         return XMADDR(((phys_addr_t)pte_mfn(*pte) << PAGE_SHIFT) + offset);
 }
 
@@ -410,7 +420,7 @@ void xen_ptep_modify_prot_commit(struct mm_struct *mm, unsigned long addr,
 
         xen_mc_batch();
 
-        u.ptr = virt_to_machine(ptep).maddr | MMU_PT_UPDATE_PRESERVE_AD;
+        u.ptr = arbitrary_virt_to_machine(ptep).maddr | MMU_PT_UPDATE_PRESERVE_AD;
         u.val = pte_val_ma(pte);
         xen_extend_mmu_update(&u);