On Wed, Jan 03, 2024, Dapeng Mi wrote:
> If HW supports GLOBAL_CTRL MSR, enabling and disabling PMCs are moved in
> __precise_count_loop(). Thus, instructions and branches events can be
> verified against a precise count instead of a rough range.
>
> Signed-off-by: Dapeng Mi <dapeng1.mi@xxxxxxxxxxxxxxx>
> ---
> x86/pmu.c | 26 ++++++++++++++++++++++++++
> 1 file changed, 26 insertions(+)
>
> diff --git a/x86/pmu.c b/x86/pmu.c
> index 88b89ad889b9..b764827c1c3d 100644
> --- a/x86/pmu.c
> +++ b/x86/pmu.c
> @@ -25,6 +25,10 @@
> "nop; nop; nop; nop; nop; nop; nop;\n\t" \
> "loop 1b;\n\t"
>
> +/*Enable GLOBAL_CTRL + disable GLOBAL_CTRL instructions */
> +#define PRECISE_EXTRA_INSTRNS (2 + 4)
> +#define PRECISE_LOOP_INSTRNS (N * LOOP_INSTRNS + PRECISE_EXTRA_INSTRNS)
> +#define PRECISE_LOOP_BRANCHES (N)
> #define PRECISE_LOOP_ASM \
> "wrmsr;\n\t" \
> "mov %%ecx, %%edi; mov %%ebx, %%ecx;\n\t" \
> @@ -107,6 +111,24 @@ static inline void loop(u64 cntrs)
> __precise_count_loop(cntrs);
> }
>
> +static void adjust_events_range(struct pmu_event *gp_events, int branch_idx)
> +{
> + /*
> + * If HW supports GLOBAL_CTRL MSR, enabling and disabling PMCs are
> + * moved in __precise_count_loop(). Thus, instructions and branches
> + * events can be verified against a precise count instead of a rough
> + * range.
> + */
> + if (this_cpu_has_perf_global_ctrl()) {
> + /* instructions event */
> + gp_events[0].min = PRECISE_LOOP_INSTRNS;
> + gp_events[0].max = PRECISE_LOOP_INSTRNS;
> + /* branches event */
> + gp_events[branch_idx].min = PRECISE_LOOP_BRANCHES;
> + gp_events[branch_idx].max = PRECISE_LOOP_BRANCHES;
> + }
> +}
> +
> volatile uint64_t irq_received;
>
> static void cnt_overflow(isr_regs_t *regs)
> @@ -771,6 +793,7 @@ static void check_invalid_rdpmc_gp(void)
>
> int main(int ac, char **av)
> {
> + int branch_idx;
> setup_vm();
> handle_irq(PMI_VECTOR, cnt_overflow);
> buf = malloc(N*64);
> @@ -784,13 +807,16 @@ int main(int ac, char **av)
> }
> gp_events = (struct pmu_event *)intel_gp_events;
> gp_events_size = sizeof(intel_gp_events)/sizeof(intel_gp_events[0]);
> + branch_idx = 5;
This (and the follow up one) hardcoded index is hacky and more
importantly, error prone especially when code get refactored later.
Please use a proper way via macro? Eg., checking
INTEL_ARCH_BRANCHES_RETIRED_INDEX in pmu_counters_test.c might be a good
one.
> report_prefix_push("Intel");
> set_ref_cycle_expectations();
> } else {
> gp_events_size = sizeof(amd_gp_events)/sizeof(amd_gp_events[0]);
> gp_events = (struct pmu_event *)amd_gp_events;
> + branch_idx = 2;
> report_prefix_push("AMD");
> }
> + adjust_events_range(gp_events, branch_idx);
>
> printf("PMU version: %d\n", pmu.version);
> printf("GP counters: %d\n", pmu.nr_gp_counters);
> --
> 2.34.1
>
