x86: Check RTM_ALWAYS_ABORT for RTM [BZ #28033]

From

https://www.intel.com/content/www/us/en/support/articles/000059422/processors.html

* Intel TSX will be disabled by default.
* The processor will force abort all Restricted Transactional Memory (RTM)
  transactions by default.
* A new CPUID bit CPUID.07H.0H.EDX[11](RTM_ALWAYS_ABORT) will be enumerated,
  which is set to indicate to updated software that the loaded microcode is
  forcing RTM abort.
* On processors that enumerate support for RTM, the CPUID enumeration bits
  for Intel TSX (CPUID.07H.0H.EBX[11] and CPUID.07H.0H.EBX[4]) continue to
  be set by default after microcode update.
* Workloads that were benefited from Intel TSX might experience a change
  in performance.
* System software may use a new bit in Model-Specific Register (MSR) 0x10F
  TSX_FORCE_ABORT[TSX_CPUID_CLEAR] functionality to clear the Hardware Lock
  Elision (HLE) and RTM bits to indicate to software that Intel TSX is
  disabled.

1. Add RTM_ALWAYS_ABORT to CPUID features.
2. Set RTM usable only if RTM_ALWAYS_ABORT isn't set.  This skips the
string/tst-memchr-rtm etc. testcases on the affected processors, which
always fail after a microcde update.
3. Check RTM feature, instead of usability, against /proc/cpuinfo.

This fixes BZ #28033.

(cherry picked from commit ea8e465a6b8d0f26c72bcbe453a854de3abf68ec)

3 files changed, 8 insertions, 4 deletions

diff --git a/sysdeps/x86/cpu-features.c b/sysdeps/x86/cpu-features.c
index eb554b6d14..ad135a122b 100644
--- a/sysdeps/x86/cpu-features.c
+++ b/sysdeps/x86/cpu-features.c
@@ -71,7 +71,6 @@ update_usable (struct cpu_features *cpu_features)
   CPU_FEATURE_UNSET (cpu_features, INDEX_7_EDX_6);
   CPU_FEATURE_UNSET (cpu_features, INDEX_7_EDX_7);
   CPU_FEATURE_UNSET (cpu_features, INDEX_7_EDX_9);
-  CPU_FEATURE_UNSET (cpu_features, INDEX_7_EDX_11);
   CPU_FEATURE_UNSET (cpu_features, INDEX_7_EDX_12);
   CPU_FEATURE_UNSET (cpu_features, INDEX_7_EDX_13);
   CPU_FEATURE_UNSET (cpu_features, INDEX_7_EDX_17);
@@ -318,6 +317,9 @@ update_usable (struct cpu_features *cpu_features)
   /* Determine if PKU is usable.  */
   if (CPU_FEATURES_CPU_P (cpu_features, OSPKE))
     CPU_FEATURE_SET (cpu_features, PKU);
+
+  if (CPU_FEATURES_CPU_P (cpu_features, RTM_ALWAYS_ABORT))
+    CPU_FEATURE_UNSET (cpu_features, RTM);
 }
 
 static void
diff --git a/sysdeps/x86/cpu-features.h b/sysdeps/x86/cpu-features.h
index 72ea74d083..8995a15f09 100644
--- a/sysdeps/x86/cpu-features.h
+++ b/sysdeps/x86/cpu-features.h
@@ -295,7 +295,7 @@ extern const struct cpu_features *__get_cpu_features (void)
 #define bit_cpu_AVX512_VP2INTERSECT (1u << 8)
 #define bit_cpu_INDEX_7_EDX_9	(1u << 9)
 #define bit_cpu_MD_CLEAR	(1u << 10)
-#define bit_cpu_INDEX_7_EDX_11	(1u << 11)
+#define bit_cpu_RTM_ALWAYS_ABORT (1u << 11)
 #define bit_cpu_INDEX_7_EDX_12	(1u << 12)
 #define bit_cpu_INDEX_7_EDX_13	(1u << 13)
 #define bit_cpu_SERIALIZE	(1u << 14)
@@ -508,7 +508,7 @@ extern const struct cpu_features *__get_cpu_features (void)
 #define index_cpu_AVX512_VP2INTERSECT COMMON_CPUID_INDEX_7
 #define index_cpu_INDEX_7_EDX_9	COMMON_CPUID_INDEX_7
 #define index_cpu_MD_CLEAR	COMMON_CPUID_INDEX_7
-#define index_cpu_INDEX_7_EDX_11 COMMON_CPUID_INDEX_7
+#define index_cpu_RTM_ALWAYS_ABORT COMMON_CPUID_INDEX_7
 #define index_cpu_INDEX_7_EDX_12 COMMON_CPUID_INDEX_7
 #define index_cpu_INDEX_7_EDX_13 COMMON_CPUID_INDEX_7
 #define index_cpu_SERIALIZE	COMMON_CPUID_INDEX_7
@@ -721,7 +721,7 @@ extern const struct cpu_features *__get_cpu_features (void)
 #define reg_AVX512_VP2INTERSECT	edx
 #define reg_INDEX_7_EDX_9	edx
 #define reg_MD_CLEAR		edx
-#define reg_INDEX_7_EDX_11	edx
+#define reg_RTM_ALWAYS_ABORT	edx
 #define reg_INDEX_7_EDX_12	edx
 #define reg_INDEX_7_EDX_13	edx
 #define reg_SERIALIZE		edx
diff --git a/sysdeps/x86/tst-get-cpu-features.c b/sysdeps/x86/tst-get-cpu-features.c
index 080c58e70b..527de3b5d9 100644
--- a/sysdeps/x86/tst-get-cpu-features.c
+++ b/sysdeps/x86/tst-get-cpu-features.c
@@ -183,6 +183,7 @@ do_test (void)
   CHECK_CPU_FEATURE (FSRM);
   CHECK_CPU_FEATURE (AVX512_VP2INTERSECT);
   CHECK_CPU_FEATURE (MD_CLEAR);
+  CHECK_CPU_FEATURE (RTM_ALWAYS_ABORT);
   CHECK_CPU_FEATURE (SERIALIZE);
   CHECK_CPU_FEATURE (HYBRID);
   CHECK_CPU_FEATURE (TSXLDTRK);
@@ -336,6 +337,7 @@ do_test (void)
   CHECK_CPU_FEATURE_USABLE (FSRM);
   CHECK_CPU_FEATURE_USABLE (AVX512_VP2INTERSECT);
   CHECK_CPU_FEATURE_USABLE (MD_CLEAR);
+  CHECK_CPU_FEATURE_USABLE (RTM_ALWAYS_ABORT);
   CHECK_CPU_FEATURE_USABLE (SERIALIZE);
   CHECK_CPU_FEATURE_USABLE (HYBRID);
   CHECK_CPU_FEATURE_USABLE (TSXLDTRK);