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.

manual/platform.texi

@@ -525,6 +525,9 @@ capability.
 @item
 @code{RTM} -- RTM instruction extensions.
 
+@item
+@code{RTM_ALWAYS_ABORT} -- Transactions always abort, making RTM unusable.
+
 @item
 @code{SDBG} -- IA32_DEBUG_INTERFACE MSR for silicon debug.
 

sysdeps/x86/bits/platform/x86.h

@@ -211,7 +211,7 @@ enum
   x86_cpu_AVX512_VP2INTERSECT	= x86_cpu_index_7_edx + 8,
   x86_cpu_INDEX_7_EDX_9		= x86_cpu_index_7_edx + 9,
   x86_cpu_MD_CLEAR		= x86_cpu_index_7_edx + 10,
-  x86_cpu_INDEX_7_EDX_11	= x86_cpu_index_7_edx + 11,
+  x86_cpu_RTM_ALWAYS_ABORT	= x86_cpu_index_7_edx + 11,
   x86_cpu_INDEX_7_EDX_12	= x86_cpu_index_7_edx + 12,
   x86_cpu_INDEX_7_EDX_13	= x86_cpu_index_7_edx + 13,
   x86_cpu_SERIALIZE		= x86_cpu_index_7_edx + 14,

sysdeps/x86/cpu-features.c

@@ -67,7 +67,6 @@ update_usable (struct cpu_features *cpu_features)
   CPU_FEATURE_SET_USABLE (cpu_features, HLE);
   CPU_FEATURE_SET_USABLE (cpu_features, BMI2);
   CPU_FEATURE_SET_USABLE (cpu_features, ERMS);
-  CPU_FEATURE_SET_USABLE (cpu_features, RTM);
   CPU_FEATURE_SET_USABLE (cpu_features, RDSEED);
   CPU_FEATURE_SET_USABLE (cpu_features, ADX);
   CPU_FEATURE_SET_USABLE (cpu_features, CLFLUSHOPT);
@@ -83,6 +82,7 @@ update_usable (struct cpu_features *cpu_features)
   CPU_FEATURE_SET_USABLE (cpu_features, MOVDIRI);
   CPU_FEATURE_SET_USABLE (cpu_features, MOVDIR64B);
   CPU_FEATURE_SET_USABLE (cpu_features, FSRM);
+  CPU_FEATURE_SET_USABLE (cpu_features, RTM_ALWAYS_ABORT);
   CPU_FEATURE_SET_USABLE (cpu_features, SERIALIZE);
   CPU_FEATURE_SET_USABLE (cpu_features, TSXLDTRK);
   CPU_FEATURE_SET_USABLE (cpu_features, LAHF64_SAHF64);
@@ -97,6 +97,9 @@ update_usable (struct cpu_features *cpu_features)
   CPU_FEATURE_SET_USABLE (cpu_features, FSRCS);
   CPU_FEATURE_SET_USABLE (cpu_features, PTWRITE);
 
+  if (!CPU_FEATURES_CPU_P (cpu_features, RTM_ALWAYS_ABORT))
+    CPU_FEATURE_SET_USABLE (cpu_features, RTM);
+
 #if CET_ENABLED
   CPU_FEATURE_SET_USABLE (cpu_features, IBT);
   CPU_FEATURE_SET_USABLE (cpu_features, SHSTK);

sysdeps/x86/include/cpu-features.h

@@ -229,7 +229,7 @@ enum
 #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)
@@ -463,7 +463,7 @@ enum
 #define index_cpu_AVX512_VP2INTERSECT CPUID_INDEX_7
 #define index_cpu_INDEX_7_EDX_9	CPUID_INDEX_7
 #define index_cpu_MD_CLEAR	CPUID_INDEX_7
-#define index_cpu_INDEX_7_EDX_11 CPUID_INDEX_7
+#define index_cpu_RTM_ALWAYS_ABORT CPUID_INDEX_7
 #define index_cpu_INDEX_7_EDX_12 CPUID_INDEX_7
 #define index_cpu_INDEX_7_EDX_13 CPUID_INDEX_7
 #define index_cpu_SERIALIZE	CPUID_INDEX_7
@@ -697,7 +697,7 @@ enum
 #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

sysdeps/x86/tst-cpu-features-supports.c

@@ -153,7 +153,7 @@ do_test (int argc, char **argv)
   fails += CHECK_SUPPORTS (rdpid, RDPID);
   fails += CHECK_SUPPORTS (rdrnd, RDRAND);
   fails += CHECK_SUPPORTS (rdseed, RDSEED);
-  fails += CHECK_SUPPORTS (rtm, RTM);
+  fails += CHECK_CPU_SUPPORTS (rtm, RTM);
   fails += CHECK_SUPPORTS (serialize, SERIALIZE);
   fails += CHECK_SUPPORTS (sha, SHA);
   fails += CHECK_CPU_SUPPORTS (shstk, SHSTK);

sysdeps/x86/tst-get-cpu-features.c

@@ -158,6 +158,7 @@ do_test (void)
   CHECK_CPU_FEATURE (UINTR);
   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);
@@ -322,6 +323,7 @@ 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);