x86: fix /dev/mem compatibility under PAT

Add ioremap_default(), which gives a sane mapping without worrying about
type conflicts.

Use it in /dev/mem read in place of ioremap(), as with ioremap(),
any mapping of the region (other than UC_MINUS) will cause a conflict
and failure of /dev/mem read.

Should address the vbetest failure reported at:

  http://bugzilla.kernel.org/show_bug.cgi?id=11057

Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 24 insertions, 1 deletions

diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
index 2b2bb3f9b683..d1b867101e5f 100644
--- a/arch/x86/mm/ioremap.c
+++ b/arch/x86/mm/ioremap.c
@@ -300,6 +300,29 @@ void __iomem *ioremap_cache(resource_size_t phys_addr, unsigned long size)
 }
 EXPORT_SYMBOL(ioremap_cache);
 
+static void __iomem *ioremap_default(resource_size_t phys_addr,
+                                        unsigned long size)
+{
+        unsigned long flags;
+        void *ret;
+        int err;
+
+        /*
+         * - WB for WB-able memory and no other conflicting mappings
+         * - UC_MINUS for non-WB-able memory with no other conflicting mappings
+         * - Inherit from confliting mappings otherwise
+         */
+        err = reserve_memtype(phys_addr, phys_addr + size, -1, &flags);
+        if (err < 0)
+                return NULL;
+
+        ret = (void *) __ioremap_caller(phys_addr, size, flags,
+                                        __builtin_return_address(0));
+
+        free_memtype(phys_addr, phys_addr + size);
+        return (void __iomem *)ret;
+}
+
 /**
  * iounmap - Free a IO remapping
  * @addr: virtual address from ioremap_*
@@ -365,7 +388,7 @@ void *xlate_dev_mem_ptr(unsigned long phys)
         if (page_is_ram(start >> PAGE_SHIFT))
                 return __va(phys);
 
-        addr = (void *)ioremap(start, PAGE_SIZE);
+        addr = (void *)ioremap_default(start, PAGE_SIZE);
         if (addr)
                 addr = (void *)((unsigned long)addr | (phys & ~PAGE_MASK));