diff options
| author | Like Xu <like.xu@linux.intel.com> | 2020-06-13 11:09:49 +0300 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2020-07-02 16:51:46 +0300 |
| commit | 097e4311cda952dfb047f2a49d35aa5de500d474 (patch) | |
| tree | 9dc6dff0a1c21956573c584478be689113e72e0c /arch/x86/include/asm/perf_event.h | |
| parent | b2d6504761a50b9493eb4b20f6e188b673f20c32 (diff) | |
| download | linux-097e4311cda952dfb047f2a49d35aa5de500d474.tar.xz | |
perf/x86: Add constraint to create guest LBR event without hw counter
The hypervisor may request the perf subsystem to schedule a time window
to directly access the LBR records msrs for its own use. Normally, it would
create a guest LBR event with callstack mode enabled, which is scheduled
along with other ordinary LBR events on the host but in an exclusive way.
To avoid wasting a counter for the guest LBR event, the perf tracks its
hw->idx via INTEL_PMC_IDX_FIXED_VLBR and assigns it with a fake VLBR
counter with the help of new vlbr_constraint. As with the BTS event,
there is actually no hardware counter assigned for the guest LBR event.
Signed-off-by: Like Xu <like.xu@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200514083054.62538-5-like.xu@linux.intel.com
Diffstat (limited to 'arch/x86/include/asm/perf_event.h')
| -rw-r--r-- | arch/x86/include/asm/perf_event.h | 22 |
1 files changed, 21 insertions, 1 deletions
diff --git a/arch/x86/include/asm/perf_event.h b/arch/x86/include/asm/perf_event.h index 5d2c30f0df02..2df707311d17 100644 --- a/arch/x86/include/asm/perf_event.h +++ b/arch/x86/include/asm/perf_event.h @@ -192,10 +192,30 @@ struct x86_pmu_capability { #define GLOBAL_STATUS_UNC_OVF BIT_ULL(61) #define GLOBAL_STATUS_ASIF BIT_ULL(60) #define GLOBAL_STATUS_COUNTERS_FROZEN BIT_ULL(59) -#define GLOBAL_STATUS_LBRS_FROZEN BIT_ULL(58) +#define GLOBAL_STATUS_LBRS_FROZEN_BIT 58 +#define GLOBAL_STATUS_LBRS_FROZEN BIT_ULL(GLOBAL_STATUS_LBRS_FROZEN_BIT) #define GLOBAL_STATUS_TRACE_TOPAPMI BIT_ULL(55) /* + * We model guest LBR event tracing as another fixed-mode PMC like BTS. + * + * We choose bit 58 because it's used to indicate LBR stack frozen state + * for architectural perfmon v4, also we unconditionally mask that bit in + * the handle_pmi_common(), so it'll never be set in the overflow handling. + * + * With this fake counter assigned, the guest LBR event user (such as KVM), + * can program the LBR registers on its own, and we don't actually do anything + * with then in the host context. + */ +#define INTEL_PMC_IDX_FIXED_VLBR (GLOBAL_STATUS_LBRS_FROZEN_BIT) + +/* + * Pseudo-encoding the guest LBR event as event=0x00,umask=0x1b, + * since it would claim bit 58 which is effectively Fixed26. + */ +#define INTEL_FIXED_VLBR_EVENT 0x1b00 + +/* * Adaptive PEBS v4 */ |