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perf/core: Correct perf sampling with guest VMs
Previously any PMU overflow interrupt that fired while a VCPU was loaded was recorded as a guest event whether it truly was or not. This resulted in nonsense perf recordings that did not honor perf_event_attr.exclude_guest and recorded guest IPs where it should have recorded host IPs. Rework the sampling logic to only record guest samples for events with exclude_guest = 0. This way any host-only events with exclude_guest set will never see unexpected guest samples. The behaviour of events with exclude_guest = 0 is unchanged. Note that events configured to sample both host and guest may still misattribute a PMI that arrived in the host as a guest event depending on KVM arch and vendor behavior. Signed-off-by: Colton Lewis <coltonlewis@google.com> Signed-off-by: Ingo Molnar <mingo@kernel.org> Reviewed-by: Oliver Upton <oliver.upton@linux.dev> Acked-by: Mark Rutland <mark.rutland@arm.com> Acked-by: Kan Liang <kan.liang@linux.intel.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Namhyung Kim <namhyung@kernel.org> Link: https://lore.kernel.org/r/20241113190156.2145593-6-coltonlewis@google.com
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@ -10,10 +10,6 @@
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#include <asm/ptrace.h>
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#ifdef CONFIG_PERF_EVENTS
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struct pt_regs;
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extern unsigned long perf_arch_instruction_pointer(struct pt_regs *regs);
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extern unsigned long perf_arch_misc_flags(struct pt_regs *regs);
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#define perf_arch_misc_flags(regs) perf_misc_flags(regs)
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#define perf_arch_bpf_user_pt_regs(regs) ®s->user_regs
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#endif
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@ -38,31 +38,3 @@ void perf_callchain_kernel(struct perf_callchain_entry_ctx *entry,
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arch_stack_walk(callchain_trace, entry, current, regs);
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}
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unsigned long perf_arch_instruction_pointer(struct pt_regs *regs)
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{
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if (perf_guest_state())
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return perf_guest_get_ip();
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return instruction_pointer(regs);
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}
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unsigned long perf_arch_misc_flags(struct pt_regs *regs)
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{
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unsigned int guest_state = perf_guest_state();
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int misc = 0;
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if (guest_state) {
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if (guest_state & PERF_GUEST_USER)
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misc |= PERF_RECORD_MISC_GUEST_USER;
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else
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misc |= PERF_RECORD_MISC_GUEST_KERNEL;
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} else {
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if (user_mode(regs))
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misc |= PERF_RECORD_MISC_USER;
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else
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misc |= PERF_RECORD_MISC_KERNEL;
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}
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return misc;
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}
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@ -3005,9 +3005,6 @@ static unsigned long code_segment_base(struct pt_regs *regs)
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unsigned long perf_arch_instruction_pointer(struct pt_regs *regs)
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{
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if (perf_guest_state())
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return perf_guest_get_ip();
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return regs->ip + code_segment_base(regs);
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}
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@ -1676,8 +1676,9 @@ extern void perf_tp_event(u16 event_type, u64 count, void *record,
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struct task_struct *task);
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extern void perf_bp_event(struct perf_event *event, void *data);
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extern unsigned long perf_misc_flags(struct pt_regs *regs);
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extern unsigned long perf_instruction_pointer(struct pt_regs *regs);
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extern unsigned long perf_misc_flags(struct perf_event *event, struct pt_regs *regs);
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extern unsigned long perf_instruction_pointer(struct perf_event *event,
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struct pt_regs *regs);
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#ifndef perf_arch_misc_flags
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# define perf_arch_misc_flags(regs) \
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@ -1688,6 +1689,22 @@ extern unsigned long perf_instruction_pointer(struct pt_regs *regs);
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# define perf_arch_bpf_user_pt_regs(regs) regs
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#endif
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#ifndef perf_arch_guest_misc_flags
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static inline unsigned long perf_arch_guest_misc_flags(struct pt_regs *regs)
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{
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unsigned long guest_state = perf_guest_state();
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if (!(guest_state & PERF_GUEST_ACTIVE))
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return 0;
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if (guest_state & PERF_GUEST_USER)
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return PERF_RECORD_MISC_GUEST_USER;
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else
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return PERF_RECORD_MISC_GUEST_KERNEL;
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}
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# define perf_arch_guest_misc_flags(regs) perf_arch_guest_misc_flags(regs)
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#endif
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static inline bool has_branch_stack(struct perf_event *event)
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{
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return event->attr.sample_type & PERF_SAMPLE_BRANCH_STACK;
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@ -7026,13 +7026,26 @@ void perf_unregister_guest_info_callbacks(struct perf_guest_info_callbacks *cbs)
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EXPORT_SYMBOL_GPL(perf_unregister_guest_info_callbacks);
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#endif
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unsigned long perf_misc_flags(struct pt_regs *regs)
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static bool should_sample_guest(struct perf_event *event)
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{
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return !event->attr.exclude_guest && perf_guest_state();
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}
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unsigned long perf_misc_flags(struct perf_event *event,
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struct pt_regs *regs)
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{
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if (should_sample_guest(event))
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return perf_arch_guest_misc_flags(regs);
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return perf_arch_misc_flags(regs);
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}
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unsigned long perf_instruction_pointer(struct pt_regs *regs)
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unsigned long perf_instruction_pointer(struct perf_event *event,
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struct pt_regs *regs)
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{
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if (should_sample_guest(event))
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return perf_guest_get_ip();
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return perf_arch_instruction_pointer(regs);
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}
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@ -7853,7 +7866,7 @@ void perf_prepare_sample(struct perf_sample_data *data,
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__perf_event_header__init_id(data, event, filtered_sample_type);
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if (filtered_sample_type & PERF_SAMPLE_IP) {
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data->ip = perf_instruction_pointer(regs);
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data->ip = perf_instruction_pointer(event, regs);
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data->sample_flags |= PERF_SAMPLE_IP;
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}
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@ -8017,7 +8030,7 @@ void perf_prepare_header(struct perf_event_header *header,
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{
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header->type = PERF_RECORD_SAMPLE;
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header->size = perf_sample_data_size(data, event);
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header->misc = perf_misc_flags(regs);
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header->misc = perf_misc_flags(event, regs);
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/*
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* If you're adding more sample types here, you likely need to do
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