mtrr, mm, x86: enhance MTRR checks for KVA huge page mapping

This patch adds an additional argument, 'uniform', to mtrr_type_lookup(),
which returns 1 when a given range is covered uniformly by MTRRs, i.e.
the range is fully covered by a single MTRR entry or the default type.

pud_set_huge() and pmd_set_huge() are changed to check the new 'uniform'
flag to see if it is safe to create a huge page mapping to the range.
This allows them to create a huge page mapping to a range covered by a
single MTRR entry of any memory type.  It also detects a non-optimal
request properly.  They continue to check with the WB type since the WB
type has no effect even if a request spans multiple MTRR entries.

pmd_set_huge() logs a warning message to a non-optimal request so that
driver writers will be aware of such a case.  Drivers should make a
mapping request aligned to a single MTRR entry when the range is covered
by MTRRs.

Signed-off-by: Toshi Kani <toshi.kani@hp.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Robert Elliott <Elliott@hp.com>
Cc: Paul Bolle <pebolle@tiscali.nl>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/arch/x86/include/asm/mtrr.h b/arch/x86/include/asm/mtrr.h
index a174af6125782f439f45a90172dfc412f2cd3791..da8dff10f63273a64768a819e6319c2422e6275f 100644 (file)
--- a/arch/x86/include/asm/mtrr.h
+++ b/arch/x86/include/asm/mtrr.h
@@ -31,7 +31,7 @@
  * arch_phys_wc_add and arch_phys_wc_del.
  */
 # ifdef CONFIG_MTRR
-extern u8 mtrr_type_lookup(u64 addr, u64 end);
+extern u8 mtrr_type_lookup(u64 addr, u64 end, u8 *uniform);
 extern void mtrr_save_fixed_ranges(void *);
 extern void mtrr_save_state(void);
 extern int mtrr_add(unsigned long base, unsigned long size,
@@ -50,11 +50,12 @@ extern int mtrr_trim_uncached_memory(unsigned long end_pfn);
 extern int amd_special_default_mtrr(void);
 extern int phys_wc_to_mtrr_index(int handle);
 #  else
-static inline u8 mtrr_type_lookup(u64 addr, u64 end)
+static inline u8 mtrr_type_lookup(u64 addr, u64 end, u8 *uniform)
 {
        /*
         * Return no-MTRRs:
         */
+       *uniform = 1;
        return MTRR_TYPE_INVALID;
 }
 #define mtrr_save_fixed_ranges(arg) do {} while (0)

diff --git a/arch/x86/kernel/cpu/mtrr/generic.c b/arch/x86/kernel/cpu/mtrr/generic.c
index 3652e2b63b145f8a032630f9233567f90930d8ed..a83f27a89cd30ad22f75b6d911d33eede663b12c 100644 (file)
--- a/arch/x86/kernel/cpu/mtrr/generic.c
+++ b/arch/x86/kernel/cpu/mtrr/generic.c
@@ -148,19 +148,22 @@ static u8 mtrr_type_lookup_fixed(u64 start, u64 end)
  * Return Value:
  * MTRR_TYPE_(type) - Matched memory type or default memory type (unmatched)
  *
- * Output Argument:
+ * Output Arguments:
  * repeat - Set to 1 when [start:end] spanned across MTRR range and type
  *         returned corresponds only to [start:*partial_end].  Caller has
  *         to lookup again for [*partial_end:end].
+ * uniform - Set to 1 when MTRR covers the region uniformly, i.e. the region
+ *          is fully covered by a single MTRR entry or the default type.
  */
 static u8 mtrr_type_lookup_variable(u64 start, u64 end, u64 *partial_end,
-                                   int *repeat)
+                                   int *repeat, u8 *uniform)
 {
        int i;
        u64 base, mask;
        u8 prev_match, curr_match;
 
        *repeat = 0;
+       *uniform = 1;
 
        /* Make end inclusive end, instead of exclusive */
        end--;
@@ -208,6 +211,7 @@ static u8 mtrr_type_lookup_variable(u64 start, u64 end, u64 *partial_end,
 
                        end = *partial_end - 1; /* end is inclusive */
                        *repeat = 1;
+                       *uniform = 0;
                }
 
                if (!start_state)
@@ -219,6 +223,7 @@ static u8 mtrr_type_lookup_variable(u64 start, u64 end, u64 *partial_end,
                        continue;
                }
 
+               *uniform = 0;
                if (check_type_overlap(&prev_match, &curr_match))
                        return curr_match;
        }
@@ -235,13 +240,19 @@ static u8 mtrr_type_lookup_variable(u64 start, u64 end, u64 *partial_end,
  * Return Values:
  * MTRR_TYPE_(type)  - The effective MTRR type for the region
  * MTRR_TYPE_INVALID - MTRR is disabled
+ *
+ * Output Argument:
+ * uniform - Set to 1 when MTRR covers the region uniformly, i.e. the region
+ *          is fully covered by a single MTRR entry or the default type.
  */
-u8 mtrr_type_lookup(u64 start, u64 end)
+u8 mtrr_type_lookup(u64 start, u64 end, u8 *uniform)
 {
-       u8 type, prev_type;
+       u8 type, prev_type, is_uniform, dummy;
        int repeat;
        u64 partial_end;
 
+       *uniform = 1;
+
        if (!mtrr_state_set)
                return MTRR_TYPE_INVALID;
 
@@ -253,14 +264,17 @@ u8 mtrr_type_lookup(u64 start, u64 end)
         * the variable ranges.
         */
        type = mtrr_type_lookup_fixed(start, end);
-       if (type != MTRR_TYPE_INVALID)
+       if (type != MTRR_TYPE_INVALID) {
+               *uniform = 0;
                return type;
+       }
 
        /*
         * Look up the variable ranges.  Look of multiple ranges matching
         * this address and pick type as per MTRR precedence.
         */
-       type = mtrr_type_lookup_variable(start, end, &partial_end, &repeat);
+       type = mtrr_type_lookup_variable(start, end, &partial_end,
+                                        &repeat, &is_uniform);
 
        /*
         * Common path is with repeat = 0.
@@ -271,16 +285,21 @@ u8 mtrr_type_lookup(u64 start, u64 end)
        while (repeat) {
                prev_type = type;
                start = partial_end;
+               is_uniform = 0;
+
                type = mtrr_type_lookup_variable(start, end, &partial_end,
-                                                &repeat);
+                                                &repeat, &dummy);
 
-               if (check_type_overlap(&prev_type, &type))
+               if (check_type_overlap(&prev_type, &type)) {
+                       *uniform = 0;
                        return type;
+               }
        }
 
        if (mtrr_tom2 && (start >= (1ULL<<32)) && (end < mtrr_tom2))
                return MTRR_TYPE_WRBACK;
 
+       *uniform = is_uniform;
        return type;
 }
 

diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index 35af6771a95ad6c126cca1f352b896998116876e..372ad422c2c3b1596f0bc35bca2eb55cf85b4a72 100644 (file)
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -267,9 +267,9 @@ static unsigned long pat_x_mtrr_type(u64 start, u64 end,
         * request is for WB.
         */
        if (req_type == _PAGE_CACHE_MODE_WB) {
-               u8 mtrr_type;
+               u8 mtrr_type, uniform;
 
-               mtrr_type = mtrr_type_lookup(start, end);
+               mtrr_type = mtrr_type_lookup(start, end, &uniform);
                if (mtrr_type != MTRR_TYPE_WRBACK)
                        return _PAGE_CACHE_MODE_UC_MINUS;
 

diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c
index cfca4cff7eba8117258c699b7fd599da3c4a9c9f..3d6edea8087e9cc964bff15f5329aee47fc93a98 100644 (file)
--- a/arch/x86/mm/pgtable.c
+++ b/arch/x86/mm/pgtable.c
@@ -567,17 +567,18 @@ void native_set_fixmap(enum fixed_addresses idx, phys_addr_t phys,
  * pud_set_huge - setup kernel PUD mapping
  *
  * MTRR can override PAT memory types with 4KB granularity.  Therefore,
- * it does not set up a huge page when the range is covered by a non-WB
- * type of MTRR.  MTRR_TYPE_INVALID indicates that MTRR are disabled.
+ * it only sets up a huge page when the range is mapped uniformly by MTRR
+ * (i.e. the range is fully covered by a single MTRR entry or the default
+ * type) or the MTRR memory type is WB.
  *
  * Return 1 on success, and 0 when no PUD was set.
  */
 int pud_set_huge(pud_t *pud, phys_addr_t addr, pgprot_t prot)
 {
-       u8 mtrr;
+       u8 mtrr, uniform;
 
-       mtrr = mtrr_type_lookup(addr, addr + PUD_SIZE);
-       if ((mtrr != MTRR_TYPE_WRBACK) && (mtrr != MTRR_TYPE_INVALID))
+       mtrr = mtrr_type_lookup(addr, addr + PUD_SIZE, &uniform);
+       if ((!uniform) && (mtrr != MTRR_TYPE_WRBACK))
                return 0;
 
        prot = pgprot_4k_2_large(prot);
@@ -593,18 +594,22 @@ int pud_set_huge(pud_t *pud, phys_addr_t addr, pgprot_t prot)
  * pmd_set_huge - setup kernel PMD mapping
  *
  * MTRR can override PAT memory types with 4KB granularity.  Therefore,
- * it does not set up a huge page when the range is covered by a non-WB
- * type of MTRR.  MTRR_TYPE_INVALID indicates that MTRR are disabled.
+ * it only sets up a huge page when the range is mapped uniformly by MTRR
+ * (i.e. the range is fully covered by a single MTRR entry or the default
+ * type) or the MTRR memory type is WB.
  *
  * Return 1 on success, and 0 when no PMD was set.
  */
 int pmd_set_huge(pmd_t *pmd, phys_addr_t addr, pgprot_t prot)
 {
-       u8 mtrr;
+       u8 mtrr, uniform;
 
-       mtrr = mtrr_type_lookup(addr, addr + PMD_SIZE);
-       if ((mtrr != MTRR_TYPE_WRBACK) && (mtrr != MTRR_TYPE_INVALID))
+       mtrr = mtrr_type_lookup(addr, addr + PMD_SIZE, &uniform);
+       if ((!uniform) && (mtrr != MTRR_TYPE_WRBACK)) {
+               pr_warn("pmd_set_huge: requesting [mem %#010llx-%#010llx], which spans more than a single MTRR entry\n",
+                               addr, addr + PMD_SIZE);
                return 0;
+       }
 
        prot = pgprot_4k_2_large(prot);