[PATCH 4.19 39/97] x86/cpu/amd: Enable the fixed Instructions Retired counter IRPERF

Greg Kroah-Hartman
2020-02-27T14:31:20Z

From: Kim Phillips <kim.phillips@amd.com>

commit 21b5ee59ef18e27d85810584caf1f7ddc705ea83 upstream.

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, it always returns a 0 count:

BEFORE:

$ 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):

$ 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.

[ bp: Massage commit message. ]

Fixes: aaf248848db50 ("perf/x86/msr: Add AMD IRPERF (Instructions Retired) performance counter")
Signed-off-by: Kim Phillips <kim.phillips@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: stable@vger.kernel.org
Link: https://bugzilla.kernel.org/show_bug.cgi?id=206537
Link: http://lkml.kernel.org/r/20200214201805.13830-1-kim.phillips@amd.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/x86/include/asm/msr-index.h | 2 ++
arch/x86/kernel/cpu/amd.c | 14 ++++++++++++++
2 files changed, 16 insertions(+)

--- a/arch/x86/include/asm/msr-index.h
+++ b/arch/x86/include/asm/msr-index.h
@@ -455,6 +455,8 @@
#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

--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -25,6 +25,7 @@

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);

/*
@@ -983,6 +984,15 @@ static void init_amd(struct cpuinfo_x86
/* 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_amd_erratum(c, amd_erratum_1054))
+ msr_set_bit(MSR_K7_HWCR, MSR_K7_HWCR_IRPERF_EN_BIT);
}

#ifdef CONFIG_X86_32
@@ -1110,6 +1120,10 @@ 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)
{