perf/x86/amd/ibs: Handle erratum #420 only on the affected CPU family (10h)

This saves us writing the IBS control MSR twice when disabling the
event.

I searched revision guides for all families since 10h, and did not
find occurrence of erratum #420, nor anything remotely similar:
so we isolate the secondary MSR write to family 10h only.

Also unconditionally update the count mask for IBS Op implementations
that have read & writeable current count (CurCnt) fields in addition
to the MaxCnt field.  These bits were reserved on prior
implementations, and therefore shouldn't have negative impact.

Signed-off-by: Kim Phillips <kim.phillips@amd.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Fixes: c9574fe0bdb9 ("perf/x86-ibs: Implement workaround for IBS erratum #420")
Link: https://lkml.kernel.org/r/20191023150955.30292-2-kim.phillips@amd.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/events/amd/ibs.c b/arch/x86/events/amd/ibs.c
index 98ba21a..26c3635 100644 (file)
--- a/arch/x86/events/amd/ibs.c
+++ b/arch/x86/events/amd/ibs.c
@@ -377,7 +377,8 @@ static inline void perf_ibs_disable_event(struct perf_ibs *perf_ibs,
                                          struct hw_perf_event *hwc, u64 config)
 {
        config &= ~perf_ibs->cnt_mask;
-       wrmsrl(hwc->config_base, config);
+       if (boot_cpu_data.x86 == 0x10)
+               wrmsrl(hwc->config_base, config);
        config &= ~perf_ibs->enable_mask;
        wrmsrl(hwc->config_base, config);
 }
@@ -553,7 +554,8 @@ static struct perf_ibs perf_ibs_op = {
        },
        .msr                    = MSR_AMD64_IBSOPCTL,
        .config_mask            = IBS_OP_CONFIG_MASK,
-       .cnt_mask               = IBS_OP_MAX_CNT,
+       .cnt_mask               = IBS_OP_MAX_CNT | IBS_OP_CUR_CNT |
+                                 IBS_OP_CUR_CNT_RAND,
        .enable_mask            = IBS_OP_ENABLE,
        .valid_mask             = IBS_OP_VAL,
        .max_period             = IBS_OP_MAX_CNT << 4,