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-rw-r--r--arch/x86/events/amd/brs.c434
1 files changed, 434 insertions, 0 deletions
diff --git a/arch/x86/events/amd/brs.c b/arch/x86/events/amd/brs.c
new file mode 100644
index 000000000..f1bff153d
--- /dev/null
+++ b/arch/x86/events/amd/brs.c
@@ -0,0 +1,434 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Implement support for AMD Fam19h Branch Sampling feature
+ * Based on specifications published in AMD PPR Fam19 Model 01
+ *
+ * Copyright 2021 Google LLC
+ * Contributed by Stephane Eranian <eranian@google.com>
+ */
+#include <linux/kernel.h>
+#include <linux/jump_label.h>
+#include <asm/msr.h>
+#include <asm/cpufeature.h>
+
+#include "../perf_event.h"
+
+#define BRS_POISON 0xFFFFFFFFFFFFFFFEULL /* mark limit of valid entries */
+
+/* Debug Extension Configuration register layout */
+union amd_debug_extn_cfg {
+ __u64 val;
+ struct {
+ __u64 rsvd0:2, /* reserved */
+ brsmen:1, /* branch sample enable */
+ rsvd4_3:2,/* reserved - must be 0x3 */
+ vb:1, /* valid branches recorded */
+ rsvd2:10, /* reserved */
+ msroff:4, /* index of next entry to write */
+ rsvd3:4, /* reserved */
+ pmc:3, /* #PMC holding the sampling event */
+ rsvd4:37; /* reserved */
+ };
+};
+
+static inline unsigned int brs_from(int idx)
+{
+ return MSR_AMD_SAMP_BR_FROM + 2 * idx;
+}
+
+static inline unsigned int brs_to(int idx)
+{
+ return MSR_AMD_SAMP_BR_FROM + 2 * idx + 1;
+}
+
+static inline void set_debug_extn_cfg(u64 val)
+{
+ /* bits[4:3] must always be set to 11b */
+ wrmsrl(MSR_AMD_DBG_EXTN_CFG, val | 3ULL << 3);
+}
+
+static inline u64 get_debug_extn_cfg(void)
+{
+ u64 val;
+
+ rdmsrl(MSR_AMD_DBG_EXTN_CFG, val);
+ return val;
+}
+
+static bool __init amd_brs_detect(void)
+{
+ if (!cpu_feature_enabled(X86_FEATURE_BRS))
+ return false;
+
+ switch (boot_cpu_data.x86) {
+ case 0x19: /* AMD Fam19h (Zen3) */
+ x86_pmu.lbr_nr = 16;
+
+ /* No hardware filtering supported */
+ x86_pmu.lbr_sel_map = NULL;
+ x86_pmu.lbr_sel_mask = 0;
+ break;
+ default:
+ return false;
+ }
+
+ return true;
+}
+
+/*
+ * Current BRS implementation does not support branch type or privilege level
+ * filtering. Therefore, this function simply enforces these limitations. No need for
+ * a br_sel_map. Software filtering is not supported because it would not correlate well
+ * with a sampling period.
+ */
+static int amd_brs_setup_filter(struct perf_event *event)
+{
+ u64 type = event->attr.branch_sample_type;
+
+ /* No BRS support */
+ if (!x86_pmu.lbr_nr)
+ return -EOPNOTSUPP;
+
+ /* Can only capture all branches, i.e., no filtering */
+ if ((type & ~PERF_SAMPLE_BRANCH_PLM_ALL) != PERF_SAMPLE_BRANCH_ANY)
+ return -EINVAL;
+
+ return 0;
+}
+
+static inline int amd_is_brs_event(struct perf_event *e)
+{
+ return (e->hw.config & AMD64_RAW_EVENT_MASK) == AMD_FAM19H_BRS_EVENT;
+}
+
+int amd_brs_hw_config(struct perf_event *event)
+{
+ int ret = 0;
+
+ /*
+ * Due to interrupt holding, BRS is not recommended in
+ * counting mode.
+ */
+ if (!is_sampling_event(event))
+ return -EINVAL;
+
+ /*
+ * Due to the way BRS operates by holding the interrupt until
+ * lbr_nr entries have been captured, it does not make sense
+ * to allow sampling on BRS with an event that does not match
+ * what BRS is capturing, i.e., retired taken branches.
+ * Otherwise the correlation with the event's period is even
+ * more loose:
+ *
+ * With retired taken branch:
+ * Effective P = P + 16 + X
+ * With any other event:
+ * Effective P = P + Y + X
+ *
+ * Where X is the number of taken branches due to interrupt
+ * skid. Skid is large.
+ *
+ * Where Y is the occurences of the event while BRS is
+ * capturing the lbr_nr entries.
+ *
+ * By using retired taken branches, we limit the impact on the
+ * Y variable. We know it cannot be more than the depth of
+ * BRS.
+ */
+ if (!amd_is_brs_event(event))
+ return -EINVAL;
+
+ /*
+ * BRS implementation does not work with frequency mode
+ * reprogramming of the period.
+ */
+ if (event->attr.freq)
+ return -EINVAL;
+ /*
+ * The kernel subtracts BRS depth from period, so it must
+ * be big enough.
+ */
+ if (event->attr.sample_period <= x86_pmu.lbr_nr)
+ return -EINVAL;
+
+ /*
+ * Check if we can allow PERF_SAMPLE_BRANCH_STACK
+ */
+ ret = amd_brs_setup_filter(event);
+
+ /* only set in case of success */
+ if (!ret)
+ event->hw.flags |= PERF_X86_EVENT_AMD_BRS;
+
+ return ret;
+}
+
+/* tos = top of stack, i.e., last valid entry written */
+static inline int amd_brs_get_tos(union amd_debug_extn_cfg *cfg)
+{
+ /*
+ * msroff: index of next entry to write so top-of-stack is one off
+ * if BRS is full then msroff is set back to 0.
+ */
+ return (cfg->msroff ? cfg->msroff : x86_pmu.lbr_nr) - 1;
+}
+
+/*
+ * make sure we have a sane BRS offset to begin with
+ * especially with kexec
+ */
+void amd_brs_reset(void)
+{
+ if (!cpu_feature_enabled(X86_FEATURE_BRS))
+ return;
+
+ /*
+ * Reset config
+ */
+ set_debug_extn_cfg(0);
+
+ /*
+ * Mark first entry as poisoned
+ */
+ wrmsrl(brs_to(0), BRS_POISON);
+}
+
+int __init amd_brs_init(void)
+{
+ if (!amd_brs_detect())
+ return -EOPNOTSUPP;
+
+ pr_cont("%d-deep BRS, ", x86_pmu.lbr_nr);
+
+ return 0;
+}
+
+void amd_brs_enable(void)
+{
+ struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
+ union amd_debug_extn_cfg cfg;
+
+ /* Activate only on first user */
+ if (++cpuc->brs_active > 1)
+ return;
+
+ cfg.val = 0; /* reset all fields */
+ cfg.brsmen = 1; /* enable branch sampling */
+
+ /* Set enable bit */
+ set_debug_extn_cfg(cfg.val);
+}
+
+void amd_brs_enable_all(void)
+{
+ struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
+ if (cpuc->lbr_users)
+ amd_brs_enable();
+}
+
+void amd_brs_disable(void)
+{
+ struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
+ union amd_debug_extn_cfg cfg;
+
+ /* Check if active (could be disabled via x86_pmu_disable_all()) */
+ if (!cpuc->brs_active)
+ return;
+
+ /* Only disable for last user */
+ if (--cpuc->brs_active)
+ return;
+
+ /*
+ * Clear the brsmen bit but preserve the others as they contain
+ * useful state such as vb and msroff
+ */
+ cfg.val = get_debug_extn_cfg();
+
+ /*
+ * When coming in on interrupt and BRS is full, then hw will have
+ * already stopped BRS, no need to issue wrmsr again
+ */
+ if (cfg.brsmen) {
+ cfg.brsmen = 0;
+ set_debug_extn_cfg(cfg.val);
+ }
+}
+
+void amd_brs_disable_all(void)
+{
+ struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
+ if (cpuc->lbr_users)
+ amd_brs_disable();
+}
+
+static bool amd_brs_match_plm(struct perf_event *event, u64 to)
+{
+ int type = event->attr.branch_sample_type;
+ int plm_k = PERF_SAMPLE_BRANCH_KERNEL | PERF_SAMPLE_BRANCH_HV;
+ int plm_u = PERF_SAMPLE_BRANCH_USER;
+
+ if (!(type & plm_k) && kernel_ip(to))
+ return 0;
+
+ if (!(type & plm_u) && !kernel_ip(to))
+ return 0;
+
+ return 1;
+}
+
+/*
+ * Caller must ensure amd_brs_inuse() is true before calling
+ * return:
+ */
+void amd_brs_drain(void)
+{
+ struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
+ struct perf_event *event = cpuc->events[0];
+ struct perf_branch_entry *br = cpuc->lbr_entries;
+ union amd_debug_extn_cfg cfg;
+ u32 i, nr = 0, num, tos, start;
+ u32 shift = 64 - boot_cpu_data.x86_virt_bits;
+
+ /*
+ * BRS event forced on PMC0,
+ * so check if there is an event.
+ * It is possible to have lbr_users > 0 but the event
+ * not yet scheduled due to long latency PMU irq
+ */
+ if (!event)
+ goto empty;
+
+ cfg.val = get_debug_extn_cfg();
+
+ /* Sanity check [0-x86_pmu.lbr_nr] */
+ if (WARN_ON_ONCE(cfg.msroff >= x86_pmu.lbr_nr))
+ goto empty;
+
+ /* No valid branch */
+ if (cfg.vb == 0)
+ goto empty;
+
+ /*
+ * msr.off points to next entry to be written
+ * tos = most recent entry index = msr.off - 1
+ * BRS register buffer saturates, so we know we have
+ * start < tos and that we have to read from start to tos
+ */
+ start = 0;
+ tos = amd_brs_get_tos(&cfg);
+
+ num = tos - start + 1;
+
+ /*
+ * BRS is only one pass (saturation) from MSROFF to depth-1
+ * MSROFF wraps to zero when buffer is full
+ */
+ for (i = 0; i < num; i++) {
+ u32 brs_idx = tos - i;
+ u64 from, to;
+
+ rdmsrl(brs_to(brs_idx), to);
+
+ /* Entry does not belong to us (as marked by kernel) */
+ if (to == BRS_POISON)
+ break;
+
+ /*
+ * Sign-extend SAMP_BR_TO to 64 bits, bits 61-63 are reserved.
+ * Necessary to generate proper virtual addresses suitable for
+ * symbolization
+ */
+ to = (u64)(((s64)to << shift) >> shift);
+
+ if (!amd_brs_match_plm(event, to))
+ continue;
+
+ rdmsrl(brs_from(brs_idx), from);
+
+ perf_clear_branch_entry_bitfields(br+nr);
+
+ br[nr].from = from;
+ br[nr].to = to;
+
+ nr++;
+ }
+empty:
+ /* Record number of sampled branches */
+ cpuc->lbr_stack.nr = nr;
+}
+
+/*
+ * Poison most recent entry to prevent reuse by next task
+ * required because BRS entry are not tagged by PID
+ */
+static void amd_brs_poison_buffer(void)
+{
+ union amd_debug_extn_cfg cfg;
+ unsigned int idx;
+
+ /* Get current state */
+ cfg.val = get_debug_extn_cfg();
+
+ /* idx is most recently written entry */
+ idx = amd_brs_get_tos(&cfg);
+
+ /* Poison target of entry */
+ wrmsrl(brs_to(idx), BRS_POISON);
+}
+
+/*
+ * On context switch in, we need to make sure no samples from previous user
+ * are left in the BRS.
+ *
+ * On ctxswin, sched_in = true, called after the PMU has started
+ * On ctxswout, sched_in = false, called before the PMU is stopped
+ */
+void amd_pmu_brs_sched_task(struct perf_event_context *ctx, bool sched_in)
+{
+ struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
+
+ /* no active users */
+ if (!cpuc->lbr_users)
+ return;
+
+ /*
+ * On context switch in, we need to ensure we do not use entries
+ * from previous BRS user on that CPU, so we poison the buffer as
+ * a faster way compared to resetting all entries.
+ */
+ if (sched_in)
+ amd_brs_poison_buffer();
+}
+
+/*
+ * called from ACPI processor_idle.c or acpi_pad.c
+ * with interrupts disabled
+ */
+void perf_amd_brs_lopwr_cb(bool lopwr_in)
+{
+ struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
+ union amd_debug_extn_cfg cfg;
+
+ /*
+ * on mwait in, we may end up in non C0 state.
+ * we must disable branch sampling to avoid holding the NMI
+ * for too long. We disable it in hardware but we
+ * keep the state in cpuc, so we can re-enable.
+ *
+ * The hardware will deliver the NMI if needed when brsmen cleared
+ */
+ if (cpuc->brs_active) {
+ cfg.val = get_debug_extn_cfg();
+ cfg.brsmen = !lopwr_in;
+ set_debug_extn_cfg(cfg.val);
+ }
+}
+
+DEFINE_STATIC_CALL_NULL(perf_lopwr_cb, perf_amd_brs_lopwr_cb);
+EXPORT_STATIC_CALL_TRAMP_GPL(perf_lopwr_cb);
+
+void __init amd_brs_lopwr_init(void)
+{
+ static_call_update(perf_lopwr_cb, perf_amd_brs_lopwr_cb);
+}