1 files changed, 9 insertions, 0 deletions

diff --git a/arch/x86/pci/i386.c b/arch/x86/pci/i386.c
index a70a85de5e84..52e656f17781 100644
--- a/arch/x86/pci/i386.c
+++ b/arch/x86/pci/i386.c
@@ -280,6 +280,15 @@ int pci_mmap_page_range(struct pci_dev *dev, struct vm_area_struct *vma,
                 return -EINVAL;
 
         prot = pgprot_val(vma->vm_page_prot);
+
+        /*
+         * Return error if pat is not enabled and write_combine is requested.
+         * Caller can followup with UC MINUS request and add a WC mtrr if there
+         * is a free mtrr slot.
+         */
+        if (!pat_enabled && write_combine)
+                return -EINVAL;
+
         if (pat_enabled && write_combine)
                 prot |= _PAGE_CACHE_WC;
         else if (pat_enabled || boot_cpu_data.x86 > 3)