x86, pat: Sanity check remap_pfn_range for RAM region

Add sanity check for remap_pfn_range of RAM regions using
lookup_memtype(). Previously, we did not have anyway to get the type of
RAM memory regions as they were tracked using a single bit in
page_struct (WB, nonWB). Now we can get the actual type from page struct
(WB, WC, UC_MINUS) and make sure the requester gets that type.

Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index b629f75f73deef2376be6233d55ef820b9e9e238..a6cace0694a2a47ff60020c14c813383adf2ea4a 100644 (file)
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -783,11 +783,29 @@ static int reserve_pfn_range(u64 paddr, unsigned long size, pgprot_t *vma_prot,
        is_ram = pat_pagerange_is_ram(paddr, paddr + size);
 
        /*
-        * reserve_pfn_range() doesn't support RAM pages. Maintain the current
-        * behavior with RAM pages by returning success.
+        * reserve_pfn_range() for RAM pages. We do not refcount to keep
+        * track of number of mappings of RAM pages. We can assert that
+        * the type requested matches the type of first page in the range.
         */
-       if (is_ram != 0)
+       if (is_ram) {
+               if (!pat_enabled)
+                       return 0;
+
+               flags = lookup_memtype(paddr);
+               if (want_flags != flags) {
+                       printk(KERN_WARNING
+                       "%s:%d map pfn RAM range req %s for %Lx-%Lx, got %s\n",
+                               current->comm, current->pid,
+                               cattr_name(want_flags),
+                               (unsigned long long)paddr,
+                               (unsigned long long)(paddr + size),
+                               cattr_name(flags));
+                       *vma_prot = __pgprot((pgprot_val(*vma_prot) &
+                                             (~_PAGE_CACHE_MASK)) |
+                                            flags);
+               }
                return 0;
+       }
 
        ret = reserve_memtype(paddr, paddr + size, want_flags, &flags);
        if (ret)