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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 ea8e465a6b)
This commit is contained in:
H.J. Lu 2021-06-30 10:47:06 -07:00
parent b0fcf88672
commit 277331ee21
2 changed files with 6 additions and 0 deletions
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3
sysdeps/x86/cpu-features.c
View File

@ -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;

3
sysdeps/x86/cpu-features.h
View File

@ -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