Re: [RFC PATCH 4/4] perf: arm_pmuv3: Keep out of guest counter partition

On 27/01/2025 22:20, Colton Lewis wrote:

If the PMU is partitioned, keep the driver out of the guest counter partition and only use the host counter partition. Partitioning is defined by the MDCR_EL2.HPMN register field and saved in cpu_pmu->hpmn. The range 0..HPMN-1 is accessible by EL1 and EL0 while HPMN..PMCR.N is reserved for EL2.

Define some macros that take HPMN as an argument and construct mutually exclusive bitmaps for testing which partition a particular counter is in. Note that despite their different position in the bitmap, the cycle and instruction counters are always in the guest partition.

Signed-off-by: Colton Lewis coltonlewis@google.com

drivers/perf/arm_pmuv3.c | 72 +++++++++++++++++++++++++++++----- include/linux/perf/arm_pmuv3.h | 8 ++++ 2 files changed, 70 insertions(+), 10 deletions(-)

diff --git a/drivers/perf/arm_pmuv3.c b/drivers/perf/arm_pmuv3.c index 55f9ae560715..c61845fad9d9 100644 --- a/drivers/perf/arm_pmuv3.c +++ b/drivers/perf/arm_pmuv3.c @@ -754,15 +754,19 @@ static void armv8pmu_disable_event_irq(struct perf_event *event) armv8pmu_disable_intens(BIT(event->hw.idx)); } -static u64 armv8pmu_getreset_flags(void) +static u64 armv8pmu_getreset_flags(struct arm_pmu *cpu_pmu) { u64 value; /* Read */ value = read_pmovsclr();

• if (cpu_pmu->partitioned)

• value &= ARMV8_PMU_HOST_CNT_PART(cpu_pmu->hpmn);
  

• else

• value &= ARMV8_PMU_OVERFLOWED_MASK;
  

• /* Write to clear flags */

• value &= ARMV8_PMU_OVERFLOWED_MASK; write_pmovsclr(value);

return value; @@ -789,6 +793,18 @@ static void armv8pmu_disable_user_access(void) update_pmuserenr(0); } +static bool armv8pmu_is_guest_part(struct arm_pmu *cpu_pmu, u8 idx) +{

• return cpu_pmu->partitioned &&

• (BIT(idx) & ARMV8_PMU_GUEST_CNT_PART(cpu_pmu->hpmn));
  

+}

+static bool armv8pmu_is_host_part(struct arm_pmu *cpu_pmu, u8 idx) +{

• return !cpu_pmu->partitioned ||

• (BIT(idx) & ARMV8_PMU_HOST_CNT_PART(cpu_pmu->hpmn));
  

+}

• static void armv8pmu_enable_user_access(struct arm_pmu *cpu_pmu) { int i;

@@ -797,6 +813,8 @@ static void armv8pmu_enable_user_access(struct arm_pmu *cpu_pmu) if (is_pmuv3p9(cpu_pmu->pmuver)) { u64 mask = 0; for_each_set_bit(i, cpuc->used_mask, ARMPMU_MAX_HWEVENTS) {

• 	if (armv8pmu_is_guest_part(cpu_pmu, i))
  

• 		continue;
  if (armv8pmu_event_has_user_read(cpuc->events[i]))
  	mask |= BIT(i);
  

  }

@@ -805,6 +823,8 @@ static void armv8pmu_enable_user_access(struct arm_pmu *cpu_pmu) /* Clear any unused counters to avoid leaking their contents */ for_each_andnot_bit(i, cpu_pmu->cntr_mask, cpuc->used_mask, ARMPMU_MAX_HWEVENTS) {

• 	if (armv8pmu_is_guest_part(cpu_pmu, i))
  

• 		continue;
  if (i == ARMV8_PMU_CYCLE_IDX)
  	write_pmccntr(0);
  else if (i == ARMV8_PMU_INSTR_IDX)
  

@@ -850,7 +870,10 @@ static void armv8pmu_start(struct arm_pmu *cpu_pmu) armv8pmu_disable_user_access(); /* Enable all counters */

• armv8pmu_pmcr_write(armv8pmu_pmcr_read() | ARMV8_PMU_PMCR_E);

• if (cpu_pmu->partitioned)

• armv8pmu_mdcr_write(armv8pmu_mdcr_read() | ARMV8_PMU_MDCR_HPME);
  

• else

• armv8pmu_pmcr_write(armv8pmu_pmcr_read() | ARMV8_PMU_PMCR_E);
  

kvm_vcpu_pmu_resync_el0(); } @@ -858,7 +881,10 @@ static void armv8pmu_start(struct arm_pmu *cpu_pmu) static void armv8pmu_stop(struct arm_pmu *cpu_pmu) { /* Disable all counters */

• armv8pmu_pmcr_write(armv8pmu_pmcr_read() & ~ARMV8_PMU_PMCR_E);

• if (cpu_pmu->partitioned)

• armv8pmu_mdcr_write(armv8pmu_pmcr_read() & ~ARMV8_PMU_MDCR_HPME);
  

typo: s/armv8pmu_pmcr_read/armv8pmu_mdcr_read

Suzuki

• else

• armv8pmu_pmcr_write(armv8pmu_pmcr_read() & ~ARMV8_PMU_PMCR_E);
  

  }

static irqreturn_t armv8pmu_handle_irq(struct arm_pmu *cpu_pmu) @@ -872,7 +898,7 @@ static irqreturn_t armv8pmu_handle_irq(struct arm_pmu *cpu_pmu) /* * Get and reset the IRQ flags */

• pmovsr = armv8pmu_getreset_flags();

• pmovsr = armv8pmu_getreset_flags(cpu_pmu);

/* * Did an overflow occur? @@ -930,6 +956,8 @@ static int armv8pmu_get_single_idx(struct pmu_hw_events *cpuc, int idx; for_each_set_bit(idx, cpu_pmu->cntr_mask, ARMV8_PMU_MAX_GENERAL_COUNTERS) {

• if (armv8pmu_is_guest_part(cpu_pmu, idx))
  

• 	continue;
  

  if (!test_and_set_bit(idx, cpuc->used_mask)) return idx; }

@@ -946,6 +974,8 @@ static int armv8pmu_get_chain_idx(struct pmu_hw_events *cpuc, * the lower idx must be even. */ for_each_set_bit(idx, cpu_pmu->cntr_mask, ARMV8_PMU_MAX_GENERAL_COUNTERS) {

• if (armv8pmu_is_guest_part(cpu_pmu, idx))
  

• 	continue;
  

  if (!(idx & 0x1)) continue; if (!test_and_set_bit(idx, cpuc->used_mask)) {

@@ -968,6 +998,7 @@ static int armv8pmu_get_event_idx(struct pmu_hw_events *cpuc, /* Always prefer to place a cycle counter into the cycle counter. */ if ((evtype == ARMV8_PMUV3_PERFCTR_CPU_CYCLES) &&

•    !cpu_pmu->partitioned &&
   !armv8pmu_event_get_threshold(&event->attr)) {
  

  if (!test_and_set_bit(ARMV8_PMU_CYCLE_IDX, cpuc->used_mask)) return ARMV8_PMU_CYCLE_IDX;

@@ -983,6 +1014,7 @@ static int armv8pmu_get_event_idx(struct pmu_hw_events *cpuc, * may not know how to handle it. */ if ((evtype == ARMV8_PMUV3_PERFCTR_INST_RETIRED) &&

•    !cpu_pmu->partitioned &&
   !armv8pmu_event_get_threshold(&event->attr) &&
   test_bit(ARMV8_PMU_INSTR_IDX, cpu_pmu->cntr_mask) &&
   !armv8pmu_event_want_user_access(event)) {
  

@@ -994,7 +1026,7 @@ static int armv8pmu_get_event_idx(struct pmu_hw_events *cpuc, * Otherwise use events counters */ if (armv8pmu_event_is_chained(event))

• return	armv8pmu_get_chain_idx(cpuc, cpu_pmu);
  

• return armv8pmu_get_chain_idx(cpuc, cpu_pmu);
  

  else return armv8pmu_get_single_idx(cpuc, cpu_pmu); }

@@ -1086,6 +1118,15 @@ static int armv8pmu_set_event_filter(struct hw_perf_event *event, return 0; } +static void armv8pmu_reset_host_counters(struct arm_pmu *cpu_pmu) +{

• int idx;
• for_each_set_bit(idx, cpu_pmu->cntr_mask, ARMV8_PMU_MAX_GENERAL_COUNTERS)

• if (armv8pmu_is_host_part(cpu_pmu, idx))
  

• 	armv8pmu_write_evcntr(idx, 0);
  

+}

• static void armv8pmu_reset(void *info) { struct arm_pmu *cpu_pmu = (struct arm_pmu *)info;

@@ -1093,8 +1134,10 @@ static void armv8pmu_reset(void *info) bitmap_to_arr64(&mask, cpu_pmu->cntr_mask, ARMPMU_MAX_HWEVENTS);

• if (cpu_pmu->partitioned)

• if (cpu_pmu->partitioned) { armv8pmu_partition(cpu_pmu->hpmn);

• mask &= ARMV8_PMU_HOST_CNT_PART(cpu_pmu->hpmn);
  

• }

/* The counter and interrupt enable registers are unknown at reset. */ armv8pmu_disable_counter(mask); @@ -1103,11 +1146,20 @@ static void armv8pmu_reset(void *info) /* Clear the counters we flip at guest entry/exit */ kvm_clr_pmu_events(mask);

• pmcr = ARMV8_PMU_PMCR_LC;
• /*

• * Initialize & Reset PMNC. Request overflow interrupt for
  

• * 64 bit cycle counter but cheat in armv8pmu_write_counter().
  

• * Initialize & Reset PMNC. Request overflow interrupt for 64
  

• * bit cycle counter but cheat in armv8pmu_write_counter().
  

• *
  

• * When partitioned, there is no single bit to reset only the
  

• * host counters. so reset them individually.
  

  */

• pmcr = ARMV8_PMU_PMCR_P | ARMV8_PMU_PMCR_C | ARMV8_PMU_PMCR_LC;

• if (cpu_pmu->partitioned)

• armv8pmu_reset_host_counters(cpu_pmu);
  

• else

• pmcr = ARMV8_PMU_PMCR_P | ARMV8_PMU_PMCR_C;
  

/* Enable long event counter support where available */ if (armv8pmu_has_long_event(cpu_pmu)) diff --git a/include/linux/perf/arm_pmuv3.h b/include/linux/perf/arm_pmuv3.h index 115ee39f693a..5f8b143794ce 100644 --- a/include/linux/perf/arm_pmuv3.h +++ b/include/linux/perf/arm_pmuv3.h @@ -247,6 +247,14 @@ #define ARMV8_PMU_OVSR_F ARMV8_PMU_CNT_MASK_F /* Mask for writable bits is both P and C fields */ #define ARMV8_PMU_OVERFLOWED_MASK ARMV8_PMU_CNT_MASK_ALL

+/* Masks for guest and host counter partitions */ +#define ARMV8_PMU_HPMN_CNT_MASK(N) GENMASK((N) - 1, 0) +#define ARMV8_PMU_GUEST_CNT_PART(N) (ARMV8_PMU_HPMN_CNT_MASK(N) | \

• 			 ARMV8_PMU_CNT_MASK_C | \
  

• 			 ARMV8_PMU_CNT_MASK_F)
  

+#define ARMV8_PMU_HOST_CNT_PART(N) (ARMV8_PMU_CNT_MASK_ALL & \

• 			 ~ARMV8_PMU_GUEST_CNT_PART(N))
  

  /*
  • PMXEVTYPER: Event selection reg
  */