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Date:   Wed, 9 Jun 2021 13:58:02 -0700
From:   Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
To:     Thomas Gleixner <tglx@linutronix.de>,
        Borislav Petkov <bp@alien8.de>
Cc:     Jonathan Corbet <corbet@lwn.net>,
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        Jiri Olsa <jolsa@redhat.com>,
        Namhyung Kim <namhyung@kernel.org>, x86@kernel.org,
        "H. Peter Anvin" <hpa@zytor.com>,
        "Paul E. McKenney" <paulmck@kernel.org>,
        Randy Dunlap <rdunlap@infradead.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        "Maciej W. Rozycki" <macro@orcam.me.uk>,
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        linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org
Subject: [PATCH 1/4] x86/msr: Define new bits in TSX_FORCE_ABORT MSR
Message-ID: <4a258368e1797d592d4b16f124bd88cf9c21ac35.1623272033.git-series.pawan.kumar.gupta@linux.intel.com>
References: <cover.2d906c322f72ec1420955136ebaa7a4c5073917c.1623272033.git-series.pawan.kumar.gupta@linux.intel.com>
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Precedence: bulk

Intel client processors that support IA32_TSX_FORCE_ABORT MSR related to
perf counter interaction [1] received a microcode update that deprecates
Transactional Synchronization Extension (TSX) feature. MSR
IA32_TSX_FORCE_ABORT bit FORCE_ABORT_RTM now defaults to 1, writes to
this bit are ignored. A new bit TSX_CPUID_CLEAR clears the TSX related
CPUID bits.

Below is the summary of changes to IA32_TSX_FORCE_ABORT MSR:

  Bit 0: FORCE_ABORT_RTM (legacy bit, new default=1) Status bit that
  indicates if RTM transactions are always aborted. This bit is
  essentially !SDV_ENABLE_RTM(Bit 2). Writes to this bit are ignored.

  Bit 1: TSX_CPUID_CLEAR (new bit, default=0) When set, CPUID.HLE = 0
  and CPUID.RTM = 0.

  Bit 2: SDV_ENABLE_RTM (new bit, default=0) When clear, XBEGIN will
  always abort with EAX code 0. When set, XBEGIN will not be forced to
  abort (but will always abort in SGX enclaves). This bit is intended to
  be SDV-only. If this bit is set transactional atomicity correctness is
  not certain.

Performance monitoring counter 3 is usable in all cases, regardless of
the value of above bits.

A new CPUID bit CPUID.RTM_ALWAYS_ABORT (CPUID 7.EDX[11]) is added to
indicate the status of always abort behavior.

Define these new CPUID and MSR bits.

[1] Performance Monitoring Impact of Intel® Transactional Synchronization Extension Memory
    http://cdrdv2.intel.com/v1/dl/getContent/604224

Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Reviewed-by: Andi Kleen <ak@linux.intel.com>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Tested-by: Neelima Krishnan <neelima.krishnan@intel.com>
---
 arch/x86/include/asm/cpufeatures.h | 1 +
 arch/x86/include/asm/msr-index.h   | 4 ++++
 2 files changed, 5 insertions(+)

diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index ac37830ae941..21c1855b5c14 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -378,6 +378,7 @@
 #define X86_FEATURE_AVX512_VP2INTERSECT (18*32+ 8) /* AVX-512 Intersect for D/Q */
 #define X86_FEATURE_SRBDS_CTRL		(18*32+ 9) /* "" SRBDS mitigation MSR available */
 #define X86_FEATURE_MD_CLEAR		(18*32+10) /* VERW clears CPU buffers */
+#define X86_FEATURE_RTM_ALWAYS_ABORT	(18*32+11) /* "" RTM transaction always aborts */
 #define X86_FEATURE_TSX_FORCE_ABORT	(18*32+13) /* "" TSX_FORCE_ABORT */
 #define X86_FEATURE_SERIALIZE		(18*32+14) /* SERIALIZE instruction */
 #define X86_FEATURE_HYBRID_CPU		(18*32+15) /* "" This part has CPUs of more than one type */
diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
index 211ba3375ee9..a7c413432b33 100644
--- a/arch/x86/include/asm/msr-index.h
+++ b/arch/x86/include/asm/msr-index.h
@@ -772,6 +772,10 @@
 
 #define MSR_TFA_RTM_FORCE_ABORT_BIT	0
 #define MSR_TFA_RTM_FORCE_ABORT		BIT_ULL(MSR_TFA_RTM_FORCE_ABORT_BIT)
+#define MSR_TFA_TSX_CPUID_CLEAR_BIT	1
+#define MSR_TFA_TSX_CPUID_CLEAR		BIT_ULL(MSR_TFA_TSX_CPUID_CLEAR_BIT)
+#define MSR_TFA_SDV_ENABLE_RTM_BIT	2
+#define MSR_TFA_SDV_ENABLE_RTM		BIT_ULL(MSR_TFA_SDV_ENABLE_RTM_BIT)
 
 /* P4/Xeon+ specific */
 #define MSR_IA32_MCG_EAX		0x00000180
-- 
git-series 0.9.1