[PATCH][x86_64] Disable TSX on some Haswell processors

[Andrew Senkevich]

Hi,

this is a workaround which disables TSX on some Haswell processors to
avoid TSX on kernel's that weren't updated with the latest microcode
package (which is needed to disable TSX by default due to errata).
Is this patch Ok?

2016-12-13  Andrew Senkevich  <andrew.senkevich@intel.com>

        * sysdeps/x86/cpu-features.c (get_common_indeces): Add
stepping identification.
        (init_cpu_features): Add handle of Haswell.

diff --git a/sysdeps/x86/cpu-features.c b/sysdeps/x86/cpu-features.c
index e228a76..a903390 100644
--- a/sysdeps/x86/cpu-features.c
+++ b/sysdeps/x86/cpu-features.c
@@ -22,7 +22,7 @@
 static void
 get_common_indeces (struct cpu_features *cpu_features,
     unsigned int *family, unsigned int *model,
-    unsigned int *extended_model)
+    unsigned int *extended_model, unsigned int *stepping)
 {
   if (family)
     {
@@ -34,6 +34,7 @@ get_common_indeces (struct cpu_features *cpu_features,
       *family = (eax >> 8) & 0x0f;
       *model = (eax >> 4) & 0x0f;
       *extended_model = (eax >> 12) & 0xf0;
+      *stepping = eax & 0x0f;
       if (*family == 0x0f)
  {
   *family += (eax >> 20) & 0xff;
@@ -116,11 +117,12 @@ init_cpu_features (struct cpu_features *cpu_features)
   /* This spells out "GenuineIntel".  */
   if (ebx == 0x756e6547 && ecx == 0x6c65746e && edx == 0x49656e69)
     {
-      unsigned int extended_model;
+      unsigned int extended_model, stepping;

       kind = arch_kind_intel;

-      get_common_indeces (cpu_features, &family, &model, &extended_model);
+      get_common_indeces (cpu_features, &family, &model, &extended_model,
+  &stepping);

       if (family == 0x06)
  {
@@ -201,6 +203,19 @@ init_cpu_features (struct cpu_features *cpu_features)
     | bit_arch_Fast_Unaligned_Copy
     | bit_arch_Prefer_PMINUB_for_stringop);
       break;
+
+    case 0x3f:
+      if (stepping >= 4)
+ break;
+    case 0x3c:
+    case 0x45:
+    case 0x46:
+      /* Disable Intel TSX on Haswell processors (except Xeon E7 v3)
+ to avoid TSX on kernel's that weren't updated with the latest
+ microcode package (which disables broken feature
+ by default).  */
+      cpu_features->cpuid[COMMON_CPUID_INDEX_7].ebx &= ~(bit_cpu_RTM);
+      break;
     }
  }

@@ -227,11 +242,12 @@ init_cpu_features (struct cpu_features *cpu_features)
   /* This spells out "AuthenticAMD".  */
   else if (ebx == 0x68747541 && ecx == 0x444d4163 && edx == 0x69746e65)
     {
-      unsigned int extended_model;
+      unsigned int extended_model, stepping;

       kind = arch_kind_amd;

-      get_common_indeces (cpu_features, &family, &model, &extended_model);
+      get_common_indeces (cpu_features, &family, &model, &extended_model,
+  &stepping);

       ecx = cpu_features->cpuid[COMMON_CPUID_INDEX_1].ecx;

@@ -268,7 +284,7 @@ init_cpu_features (struct cpu_features *cpu_features)
   else
     {
       kind = arch_kind_other;
-      get_common_indeces (cpu_features, NULL, NULL, NULL);
+      get_common_indeces (cpu_features, NULL, NULL, NULL, NULL);
     }

   /* Support i586 if CX8 is available.  */



--
WBR,
Andrew
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