x86, pat: fix warn_on_once() while mapping 0-1MB range with /dev/mem

Jeff Mahoney reported:

> With Suse's hwinfo tool, on -tip:
> WARNING: at arch/x86/mm/pat.c:637 reserve_pfn_range+0x5b/0x26d()

reserve_pfn_range() is not tracking the memory range below 1MB
as non-RAM and as such is inconsistent with similar checks in
reserve_memtype() and free_memtype()

Rename the pagerange_is_ram() to pat_pagerange_is_ram() and add the
"track legacy 1MB region as non RAM" condition.

And also, fix reserve_pfn_range() to return -EINVAL, when the pfn
range is RAM. This is to be consistent with this API design.

Reported-and-tested-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 45 insertions, 38 deletions

diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index 7b61036427df..aebbf67a79d0 100644
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -211,6 +211,33 @@ chk_conflict(struct memtype *new, struct memtype *entry, unsigned long *type)
 static struct memtype *cached_entry;
 static u64 cached_start;
 
+static int pat_pagerange_is_ram(unsigned long start, unsigned long end)
+{
+        int ram_page = 0, not_rampage = 0;
+        unsigned long page_nr;
+
+        for (page_nr = (start >> PAGE_SHIFT); page_nr < (end >> PAGE_SHIFT);
+             ++page_nr) {
+                /*
+                 * For legacy reasons, physical address range in the legacy ISA
+                 * region is tracked as non-RAM. This will allow users of
+                 * /dev/mem to map portions of legacy ISA region, even when
+                 * some of those portions are listed(or not even listed) with
+                 * different e820 types(RAM/reserved/..)
+                 */
+                if (page_nr >= (ISA_END_ADDRESS >> PAGE_SHIFT) &&
+                    page_is_ram(page_nr))
+                        ram_page = 1;
+                else
+                        not_rampage = 1;
+
+                if (ram_page == not_rampage)
+                        return -1;
+        }
+
+        return ram_page;
+}
+
 /*
  * For RAM pages, mark the pages as non WB memory type using
  * PageNonWB (PG_arch_1). We allow only one set_memory_uc() or
@@ -336,20 +363,12 @@ int reserve_memtype(u64 start, u64 end, unsigned long req_type,
         if (new_type)
                 *new_type = actual_type;
 
-        /*
-         * For legacy reasons, some parts of the physical address range in the
-         * legacy 1MB region is treated as non-RAM (even when listed as RAM in
-         * the e820 tables).  So we will track the memory attributes of this
-         * legacy 1MB region using the linear memtype_list always.
-         */
-        if (end >= ISA_END_ADDRESS) {
-                is_range_ram = pagerange_is_ram(start, end);
-                if (is_range_ram == 1)
-                        return reserve_ram_pages_type(start, end, req_type,
-                                                      new_type);
-                else if (is_range_ram < 0)
-                        return -EINVAL;
-        }
+        is_range_ram = pat_pagerange_is_ram(start, end);
+        if (is_range_ram == 1)
+                return reserve_ram_pages_type(start, end, req_type,
+                                              new_type);
+        else if (is_range_ram < 0)
+                return -EINVAL;
 
         new  = kmalloc(sizeof(struct memtype), GFP_KERNEL);
         if (!new)
@@ -446,19 +465,11 @@ int free_memtype(u64 start, u64 end)
         if (is_ISA_range(start, end - 1))
                 return 0;
 
-        /*
-         * For legacy reasons, some parts of the physical address range in the
-         * legacy 1MB region is treated as non-RAM (even when listed as RAM in
-         * the e820 tables).  So we will track the memory attributes of this
-         * legacy 1MB region using the linear memtype_list always.
-         */
-        if (end >= ISA_END_ADDRESS) {
-                is_range_ram = pagerange_is_ram(start, end);
-                if (is_range_ram == 1)
-                        return free_ram_pages_type(start, end);
-                else if (is_range_ram < 0)
-                        return -EINVAL;
-        }
+        is_range_ram = pat_pagerange_is_ram(start, end);
+        if (is_range_ram == 1)
+                return free_ram_pages_type(start, end);
+        else if (is_range_ram < 0)
+                return -EINVAL;
 
         spin_lock(&memtype_lock);
         list_for_each_entry(entry, &memtype_list, nd) {
@@ -626,17 +637,13 @@ static int reserve_pfn_range(u64 paddr, unsigned long size, pgprot_t *vma_prot,
         unsigned long flags;
         unsigned long want_flags = (pgprot_val(*vma_prot) & _PAGE_CACHE_MASK);
 
-        is_ram = pagerange_is_ram(paddr, paddr + size);
+        is_ram = pat_pagerange_is_ram(paddr, paddr + size);
 
-        if (is_ram != 0) {
-                /*
-                 * For mapping RAM pages, drivers need to call
-                 * set_memory_[uc|wc|wb] directly, for reserve and free, before
-                 * setting up the PTE.
-                 */
-                WARN_ON_ONCE(1);
-                return 0;
-        }
+        /*
+         * reserve_pfn_range() doesn't support RAM pages.
+         */
+        if (is_ram != 0)
+                return -EINVAL;
 
         ret = reserve_memtype(paddr, paddr + size, want_flags, &flags);
         if (ret)
@@ -693,7 +700,7 @@ static void free_pfn_range(u64 paddr, unsigned long size)
 {
         int is_ram;
 
-        is_ram = pagerange_is_ram(paddr, paddr + size);
+        is_ram = pat_pagerange_is_ram(paddr, paddr + size);
         if (is_ram == 0)
                 free_memtype(paddr, paddr + size);
 }