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>

1 files changed, 21 insertions, 3 deletions

diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index b629f75f73de..a6cace0694a2 100644
--- 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)