[PATCH v3] x86/cpu/amd: Enable the fixed Instructions Retired counter IRPERF

* [PATCH v3] x86/cpu/amd: Enable the fixed Instructions Retired counter IRPERF
@ 2020-02-14 20:18 Kim Phillips
  2020-02-18 11:20 ` Borislav Petkov
  2020-02-19 19:07 ` [tip: x86/urgent] " tip-bot2 for Kim Phillips
  0 siblings, 2 replies; 5+ messages in thread
From: Kim Phillips @ 2020-02-14 20:18 UTC (permalink / raw)
  To: Peter Zijlstra, Ingo Molnar, Ingo Molnar, Borislav Petkov, kim.phillips
  Cc: Alexander Shishkin, Andi Kleen, Arnaldo Carvalho de Melo,
	Babu Moger, Fenghua Yu, Frank van der Linden, H . Peter Anvin,
	Huang Rui, Janakarajan Natarajan, Jan Beulich, Jiaxun Yang,
	Jiri Olsa, Josh Poimboeuf, Linus Torvalds, Luwei Kang,
	Martin Liška, Matt Fleming, Michael Petlan, Namhyung Kim,
	Paolo Bonzini, Pawan Gupta, Suravee Suthikulpanit,
	Thomas Gleixner, Tom Lendacky, x86, linux-kernel, stable

Commit aaf248848db50 ("perf/x86/msr: Add AMD IRPERF (Instructions
Retired) performance counter") added support for access to the
free-running counter via 'perf -e msr/irperf/', but when exercised,
we always get a 0 count:

BEFORE:

$ sudo perf stat -e instructions,msr/irperf/ true

 Performance counter stats for 'true':

           624,833      instructions
                 0      msr/irperf/

Simply set its enable bit - HWCR bit 30 - to make it start counting.

Enablement is restricted to all machines advertising IRPERF capability,
except those susceptible to an erratum that makes the IRPERF return
bad values.

That erratum occurs in Family 17h models 00-1fh [1], but not in F17h
models 20h and above [2].

AFTER (on a family 17h model 31h machine):

$ sudo perf stat -e instructions,msr/irperf/ true

 Performance counter stats for 'true':

           621,690      instructions
           622,490      msr/irperf/

[1] Revision Guide for AMD Family 17h Models 00h-0Fh Processors
[2] Revision Guide for AMD Family 17h Models 30h-3Fh Processors

The revision guides are available from the bugzilla Link below.

Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Babu Moger <babu.moger@amd.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Frank van der Linden <fllinden@amazon.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Huang Rui <ray.huang@amd.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Janakarajan Natarajan <Janakarajan.Natarajan@amd.com>
Cc: Jan Beulich <jbeulich@suse.com>
Cc: Jiaxun Yang <jiaxun.yang@flygoat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luwei Kang <luwei.kang@intel.com>
Cc: Martin Liška <mliska@suse.cz>
Cc: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Michael Petlan <mpetlan@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Suravee Suthikulpanit <Suravee.Suthikulpanit@amd.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: x86@kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: stable@vger.kernel.org
Link: https://bugzilla.kernel.org/show_bug.cgi?id=206537
Fixes: aaf248848db50 ("perf/x86/msr: Add AMD IRPERF (Instructions Retired) performance counter")
Signed-off-by: Kim Phillips <kim.phillips@amd.com>
---
v3: Removed null stalled cycles per insn from perf example output,
    since it got fixed, also address comments from Borislav Petkov:

    https://lkml.org/lkml/2020/2/11/395

    - rephrase commit text to not say "this patch".
    - uploaded both rev. guides (and all public F17h PPRs)
      to a new "Add AMD x86 documents for future reference"
      bug, and reference that in a Link: tag.
    - rename X86_BUG_AMD_E1054 -> X86_BUG_IRPERF
    - add a full stop to a sentence in a comment

v2 got resent, adding Michael Petlan to cc. Original v2:

    https://lore.kernel.org/lkml/20200121171232.28839-2-kim.phillips@amd.com/

v2: Based on Andi Kleen's review:

    https://lore.kernel.org/lkml/20200116040324.GI302770@tassilo.jf.intel.com/

    Add an amd_erratum_1054 and use cpu_has_bug infrastructure
    instead of open-coding the {family,model} check.

 arch/x86/include/asm/cpufeatures.h |  1 +
 arch/x86/include/asm/msr-index.h   |  2 ++
 arch/x86/kernel/cpu/amd.c          | 17 +++++++++++++++++
 3 files changed, 20 insertions(+)

diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index f3327cb56edf..8979d6fcc79c 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -404,5 +404,6 @@
 #define X86_BUG_SWAPGS			X86_BUG(21) /* CPU is affected by speculation through SWAPGS */
 #define X86_BUG_TAA			X86_BUG(22) /* CPU is affected by TSX Async Abort(TAA) */
 #define X86_BUG_ITLB_MULTIHIT		X86_BUG(23) /* CPU may incur MCE during certain page attribute changes */
+#define X86_BUG_IRPERF			X86_BUG(24) /* CPU is affected by Instructions Retired counter Erratum 1054 */
 
 #endif /* _ASM_X86_CPUFEATURES_H */
diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
index ebe1685e92dd..d5e517d1c3dd 100644
--- a/arch/x86/include/asm/msr-index.h
+++ b/arch/x86/include/asm/msr-index.h
@@ -512,6 +512,8 @@
 #define MSR_K7_HWCR			0xc0010015
 #define MSR_K7_HWCR_SMMLOCK_BIT		0
 #define MSR_K7_HWCR_SMMLOCK		BIT_ULL(MSR_K7_HWCR_SMMLOCK_BIT)
+#define MSR_K7_HWCR_IRPERF_EN_BIT	30
+#define MSR_K7_HWCR_IRPERF_EN		BIT_ULL(MSR_K7_HWCR_IRPERF_EN_BIT)
 #define MSR_K7_FID_VID_CTL		0xc0010041
 #define MSR_K7_FID_VID_STATUS		0xc0010042
 
diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index ac83a0fef628..deebc728e2aa 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -28,6 +28,7 @@
 
 static const int amd_erratum_383[];
 static const int amd_erratum_400[];
+static const int amd_erratum_1054[];
 static bool cpu_has_amd_erratum(struct cpuinfo_x86 *cpu, const int *erratum);
 
 /*
@@ -694,6 +695,9 @@ static void early_init_amd(struct cpuinfo_x86 *c)
 	if (cpu_has_amd_erratum(c, amd_erratum_400))
 		set_cpu_bug(c, X86_BUG_AMD_E400);
 
+	if (cpu_has_amd_erratum(c, amd_erratum_1054))
+		set_cpu_bug(c, X86_BUG_IRPERF);
+
 	early_detect_mem_encrypt(c);
 
 	/* Re-enable TopologyExtensions if switched off by BIOS */
@@ -972,6 +976,15 @@ static void init_amd(struct cpuinfo_x86 *c)
 	/* AMD CPUs don't reset SS attributes on SYSRET, Xen does. */
 	if (!cpu_has(c, X86_FEATURE_XENPV))
 		set_cpu_bug(c, X86_BUG_SYSRET_SS_ATTRS);
+
+	/*
+	 * Turn on the Instructions Retired free counter on machines not
+	 * susceptible to erratum #1054 "Instructions Retired Performance
+	 * Counter May Be Inaccurate".
+	 */
+	if (cpu_has(c, X86_FEATURE_IRPERF) &&
+	    !cpu_has_bug(c, X86_BUG_IRPERF))
+		msr_set_bit(MSR_K7_HWCR, MSR_K7_HWCR_IRPERF_EN_BIT);
 }
 
 #ifdef CONFIG_X86_32
@@ -1099,6 +1112,10 @@ static const int amd_erratum_400[] =
 static const int amd_erratum_383[] =
 	AMD_OSVW_ERRATUM(3, AMD_MODEL_RANGE(0x10, 0, 0, 0xff, 0xf));
 
+/* #1054: Instructions Retired Performance Counter May Be Inaccurate */
+static const int amd_erratum_1054[] =
+	AMD_OSVW_ERRATUM(0, AMD_MODEL_RANGE(0x17, 0, 0, 0x2f, 0xf));
+
 
 static bool cpu_has_amd_erratum(struct cpuinfo_x86 *cpu, const int *erratum)
 {
-- 
2.25.0


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