x86/mm/mtrr: Fix MTRR state checks in mtrr_type_lookup()

'mtrr_state.enabled' contains the FE (fixed MTRRs enabled)
and E (MTRRs enabled) flags in MSR_MTRRdefType.  Intel SDM,
section 11.11.2.1, defines these flags as follows:

 - All MTRRs are disabled when the E flag is clear.
   The FE flag has no affect when the E flag is clear.
 - The default type is enabled when the E flag is set.
 - MTRR variable ranges are enabled when the E flag is set.
 - MTRR fixed ranges are enabled when both E and FE flags
   are set.

MTRR state checks in __mtrr_type_lookup() do not match with SDM.

Hence, this patch makes the following changes:
 - The current code detects MTRRs disabled when both E and
   FE flags are clear in mtrr_state.enabled.  Fix to detect
   MTRRs disabled when the E flag is clear.
 - The current code does not check if the FE bit is set in
   mtrr_state.enabled when looking at the fixed entries.
   Fix to check the FE flag.
 - The current code returns the default type when the E flag
   is clear in mtrr_state.enabled. However, the default type
   is UC when the E flag is clear.  Remove the code as this
   case is handled as MTRR disabled with the 1st change.

In addition, this patch defines the E and FE flags in
mtrr_state.enabled as follows.
 - FE flag: MTRR_STATE_MTRR_FIXED_ENABLED
 - E  flag: MTRR_STATE_MTRR_ENABLED

print_mtrr_state() and x86_get_mtrr_mem_range() are also updated
accordingly.

Signed-off-by: Toshi Kani <toshi.kani@hp.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Elliott@hp.com
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luis R. Rodriguez <mcgrof@suse.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dave.hansen@intel.com
Cc: linux-mm <linux-mm@kvack.org>
Cc: pebolle@tiscali.nl
Link: http://lkml.kernel.org/r/1431714237-880-4-git-send-email-toshi.kani@hp.com
Link: http://lkml.kernel.org/r/1432628901-18044-4-git-send-email-bp@alien8.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

3 files changed, 14 insertions, 8 deletions

diff --git a/arch/x86/include/asm/mtrr.h b/arch/x86/include/asm/mtrr.h
index f768f6298419..ef927948657c 100644
--- a/arch/x86/include/asm/mtrr.h
+++ b/arch/x86/include/asm/mtrr.h
@@ -127,4 +127,8 @@ struct mtrr_gentry32 {
                                  _IOW(MTRR_IOCTL_BASE,  9, struct mtrr_sentry32)
 #endif /* CONFIG_COMPAT */
 
+/* Bit fields for enabled in struct mtrr_state_type */
+#define MTRR_STATE_MTRR_FIXED_ENABLED   0x01
+#define MTRR_STATE_MTRR_ENABLED         0x02
+
 #endif /* _ASM_X86_MTRR_H */
diff --git a/arch/x86/kernel/cpu/mtrr/cleanup.c b/arch/x86/kernel/cpu/mtrr/cleanup.c
index 5f90b85ff22e..70d7c93f4550 100644
--- a/arch/x86/kernel/cpu/mtrr/cleanup.c
+++ b/arch/x86/kernel/cpu/mtrr/cleanup.c
@@ -98,7 +98,8 @@ x86_get_mtrr_mem_range(struct range *range, int nr_range,
                         continue;
                 base = range_state[i].base_pfn;
                 if (base < (1<<(20-PAGE_SHIFT)) && mtrr_state.have_fixed &&
-                    (mtrr_state.enabled & 1)) {
+                    (mtrr_state.enabled & MTRR_STATE_MTRR_ENABLED) &&
+                    (mtrr_state.enabled & MTRR_STATE_MTRR_FIXED_ENABLED)) {
                         /* Var MTRR contains UC entry below 1M? Skip it: */
                         printk(BIOS_BUG_MSG, i);
                         if (base + size <= (1<<(20-PAGE_SHIFT)))
diff --git a/arch/x86/kernel/cpu/mtrr/generic.c b/arch/x86/kernel/cpu/mtrr/generic.c
index e202d26f64a2..b0599dbb899a 100644
--- a/arch/x86/kernel/cpu/mtrr/generic.c
+++ b/arch/x86/kernel/cpu/mtrr/generic.c
@@ -119,14 +119,16 @@ static u8 __mtrr_type_lookup(u64 start, u64 end, u64 *partial_end, int *repeat)
         if (!mtrr_state_set)
                 return 0xFF;
 
-        if (!mtrr_state.enabled)
+        if (!(mtrr_state.enabled & MTRR_STATE_MTRR_ENABLED))
                 return 0xFF;
 
         /* Make end inclusive end, instead of exclusive */
         end--;
 
         /* Look in fixed ranges. Just return the type as per start */
-        if (mtrr_state.have_fixed && (start < 0x100000)) {
+        if ((start < 0x100000) &&
+            (mtrr_state.have_fixed) &&
+            (mtrr_state.enabled & MTRR_STATE_MTRR_FIXED_ENABLED)) {
                 int idx;
 
                 if (start < 0x80000) {
@@ -149,9 +151,6 @@ static u8 __mtrr_type_lookup(u64 start, u64 end, u64 *partial_end, int *repeat)
          * Look of multiple ranges matching this address and pick type
          * as per MTRR precedence
          */
-        if (!(mtrr_state.enabled & 2))
-                return mtrr_state.def_type;
-
         prev_match = 0xFF;
         for (i = 0; i < num_var_ranges; ++i) {
                 unsigned short start_state, end_state, inclusive;
@@ -355,7 +354,9 @@ static void __init print_mtrr_state(void)
                  mtrr_attrib_to_str(mtrr_state.def_type));
         if (mtrr_state.have_fixed) {
                 pr_debug("MTRR fixed ranges %sabled:\n",
-                         mtrr_state.enabled & 1 ? "en" : "dis");
+                        ((mtrr_state.enabled & MTRR_STATE_MTRR_ENABLED) &&
+                         (mtrr_state.enabled & MTRR_STATE_MTRR_FIXED_ENABLED)) ?
+                         "en" : "dis");
                 print_fixed(0x00000, 0x10000, mtrr_state.fixed_ranges + 0);
                 for (i = 0; i < 2; ++i)
                         print_fixed(0x80000 + i * 0x20000, 0x04000,
@@ -368,7 +369,7 @@ static void __init print_mtrr_state(void)
                 print_fixed_last();
         }
         pr_debug("MTRR variable ranges %sabled:\n",
-                 mtrr_state.enabled & 2 ? "en" : "dis");
+                 mtrr_state.enabled & MTRR_STATE_MTRR_ENABLED ? "en" : "dis");
         high_width = (__ffs64(size_or_mask) - (32 - PAGE_SHIFT) + 3) / 4;
 
         for (i = 0; i < num_var_ranges; ++i) {