[IA64] rework memory attribute aliasing

This closes a couple holes in our attribute aliasing avoidance scheme:

  - The current kernel fails mmaps of some /dev/mem MMIO regions because
    they don't appear in the EFI memory map.  This keeps X from working
    on the Intel Tiger box.

  - The current kernel allows UC mmap of the 0-1MB region of
    /sys/.../legacy_mem even when the chipset doesn't support UC
    access.  This causes an MCA when starting X on HP rx7620 and rx8620
    boxes in the default configuration.

There's more detail in the Documentation/ia64/aliasing.txt file this
adds, but the general idea is that if a region might be covered by
a granule-sized kernel identity mapping, any access via /dev/mem or
mmap must use the same attribute as the identity mapping.

Otherwise, we fall back to using an attribute that is supported
according to the EFI memory map, or to using UC if the EFI memory
map doesn't mention the region.

Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

1 files changed, 22 insertions, 5 deletions

diff --git a/arch/ia64/mm/ioremap.c b/arch/ia64/mm/ioremap.c
index 643ccc6960ce..07bd02b6c372 100644
--- a/arch/ia64/mm/ioremap.c
+++ b/arch/ia64/mm/ioremap.c
@@ -11,6 +11,7 @@
 #include <linux/module.h>
 #include <linux/efi.h>
 #include <asm/io.h>
+#include <asm/meminit.h>
 
 static inline void __iomem *
 __ioremap (unsigned long offset, unsigned long size)
@@ -21,16 +22,29 @@ __ioremap (unsigned long offset, unsigned long size)
 void __iomem *
 ioremap (unsigned long offset, unsigned long size)
 {
-        if (efi_mem_attribute_range(offset, size, EFI_MEMORY_WB))
-                return phys_to_virt(offset);
+        u64 attr;
+        unsigned long gran_base, gran_size;
 
-        if (efi_mem_attribute_range(offset, size, EFI_MEMORY_UC))
+        /*
+         * For things in kern_memmap, we must use the same attribute
+         * as the rest of the kernel.  For more details, see
+         * Documentation/ia64/aliasing.txt.
+         */
+        attr = kern_mem_attribute(offset, size);
+        if (attr & EFI_MEMORY_WB)
+                return phys_to_virt(offset);
+        else if (attr & EFI_MEMORY_UC)
                 return __ioremap(offset, size);
 
         /*
-         * Someday this should check ACPI resources so we
-         * can do the right thing for hot-plugged regions.
+         * Some chipsets don't support UC access to memory.  If
+         * WB is supported for the whole granule, we prefer that.
          */
+        gran_base = GRANULEROUNDDOWN(offset);
+        gran_size = GRANULEROUNDUP(offset + size) - gran_base;
+        if (efi_mem_attribute(gran_base, gran_size) & EFI_MEMORY_WB)
+                return phys_to_virt(offset);
+
         return __ioremap(offset, size);
 }
 EXPORT_SYMBOL(ioremap);
@@ -38,6 +52,9 @@ EXPORT_SYMBOL(ioremap);
 void __iomem *
 ioremap_nocache (unsigned long offset, unsigned long size)
 {
+        if (kern_mem_attribute(offset, size) & EFI_MEMORY_WB)
+                return 0;
+
         return __ioremap(offset, size);
 }
 EXPORT_SYMBOL(ioremap_nocache);