From ea8e465a6b8d0f26c72bcbe453a854de3abf68ec Mon Sep 17 00:00:00 2001
From: "H.J. Lu" <hjl.tools@gmail.com>
Date: Wed, 30 Jun 2021 10:47:06 -0700
Subject: [PATCH] x86: Check RTM_ALWAYS_ABORT for RTM [BZ #28033]
Content-type: text/plain; charset=UTF-8

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                    | 3 +++
 sysdeps/x86/cpu-features.c              | 5 ++++-
 sysdeps/x86/sys/platform/x86.h          | 6 +++---
 sysdeps/x86/tst-cpu-features-supports.c | 2 +-
 sysdeps/x86/tst-get-cpu-features.c      | 2 ++
 5 files changed, 13 insertions(+), 5 deletions(-)

Conflicts:
	sysdeps/x86/bits/platform/x86.h
	(doesn't exist)
	sysdeps/x86/bits/platform/x86.h
	(account for lack of upstream renames)

diff --git a/manual/platform.texi b/manual/platform.texi
index 8fec2933..b7e8aef7 100644
--- a/manual/platform.texi
+++ b/manual/platform.texi
@@ -510,6 +510,9 @@ 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.
 
diff --git a/sysdeps/x86/cpu-features.c b/sysdeps/x86/cpu-features.c
index 3610ee5c..4889f062 100644
--- a/sysdeps/x86/cpu-features.c
+++ b/sysdeps/x86/cpu-features.c
@@ -74,7 +74,6 @@ 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);
@@ -90,6 +89,7 @@ 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);
@@ -779,6 +779,9 @@ no_cpuid:
     GLRO(dl_platform) = "i586";
 #endif
 
+  if (!CPU_FEATURES_CPU_P (cpu_features, RTM_ALWAYS_ABORT))
+    CPU_FEATURE_SET_USABLE (cpu_features, RTM);
+
 #if CET_ENABLED
 # if HAVE_TUNABLES
   TUNABLE_GET (x86_ibt, tunable_val_t *,
diff --git a/sysdeps/x86/sys/platform/x86.h b/sysdeps/x86/sys/platform/x86.h
index e5cc7c68..7a434926 100644
--- a/sysdeps/x86/sys/platform/x86.h
+++ b/sysdeps/x86/sys/platform/x86.h
@@ -247,7 +247,7 @@ extern const struct cpu_features *__x86_get_cpu_features (unsigned int)
 #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)
@@ -471,7 +471,7 @@ extern const struct cpu_features *__x86_get_cpu_features (unsigned int)
 #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
@@ -695,7 +695,7 @@ extern const struct cpu_features *__x86_get_cpu_features (unsigned int)
 #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-cpu-features-supports.c b/sysdeps/x86/tst-cpu-features-supports.c
index 287cf01f..8100a319 100644
--- a/sysdeps/x86/tst-cpu-features-supports.c
+++ b/sysdeps/x86/tst-cpu-features-supports.c
@@ -152,7 +152,7 @@ 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);
diff --git a/sysdeps/x86/tst-get-cpu-features.c b/sysdeps/x86/tst-get-cpu-features.c
index 2763deb6..0717e5d8 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 (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);
@@ -344,6 +345,7 @@ 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);
-- 
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