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)

diff --git a/sysdeps/x86/cpu-features.c b/sysdeps/x86/cpu-features.c
index 4be4be7051b401415ced06c81a8c45b376ca18c7..90be104842ed46eeac325e3421c1092255413935 100644 (file)
--- a/sysdeps/x86/cpu-features.c
+++ b/sysdeps/x86/cpu-features.c
@@ -248,6 +248,9 @@ init_cpu_features (struct cpu_features *cpu_features)
 
       get_extended_indices (cpu_features);
 
+      if (CPU_FEATURES_CPU_P (cpu_features, RTM_ALWAYS_ABORT))
+       cpu_features->cpuid[index_cpu_RTM].reg_RTM &= ~bit_cpu_RTM;
+
       if (family == 0x06)
        {
          model += extended_model;

diff --git a/sysdeps/x86/cpu-features.h b/sysdeps/x86/cpu-features.h
index 177aa0ebc80ea8e1d45274494e77f070660a2a77..aad6c5198d81098b9b6157da59b207dce78ea09e 100644 (file)
--- a/sysdeps/x86/cpu-features.h
+++ b/sysdeps/x86/cpu-features.h
@@ -81,6 +81,7 @@
 #define bit_cpu_IBT            (1u << 20)
 #define bit_cpu_SHSTK          (1u << 7)
 #define bit_cpu_FSRM           (1 << 4)
+#define bit_cpu_RTM_ALWAYS_ABORT (1 << 11)
 
 /* XCR0 Feature flags.  */
 #define bit_XMM_state          (1 << 1)
@@ -213,6 +214,7 @@ extern const struct cpu_features *__get_cpu_features (void)
 # define index_cpu_IBT         COMMON_CPUID_INDEX_7
 # define index_cpu_SHSTK       COMMON_CPUID_INDEX_7
 # define index_cpu_FSRM                COMMON_CPUID_INDEX_7
+# define index_cpu_RTM_ALWAYS_ABORT COMMON_CPUID_INDEX_7
 
 # define reg_CX8               edx
 # define reg_CMOV              edx
@@ -245,6 +247,7 @@ extern const struct cpu_features *__get_cpu_features (void)
 # define reg_IBT               edx
 # define reg_SHSTK             ecx
 # define reg_FSRM              edx
+# define reg_RTM_ALWAYS_ABORT  edx
 
 # define index_arch_Fast_Rep_String    FEATURE_INDEX_1
 # define index_arch_Fast_Copy_Backward FEATURE_INDEX_1