| Message ID | 20240920174740.781614-6-coltonlewis@google.com (mailing list archive) |
|---|---|
| State | Handled Elsewhere |
| Headers | show |
| Series | Correct perf sampling with Guest VMs | expand |
| Context | Check | Description |
|---|---|---|
| snowpatch_ozlabs/github-powerpc_ppctests | success | Successfully ran 8 jobs. |
| snowpatch_ozlabs/github-powerpc_selftests | success | Successfully ran 8 jobs. |
| snowpatch_ozlabs/github-powerpc_sparse | success | Successfully ran 4 jobs. |
| snowpatch_ozlabs/github-powerpc_clang | success | Successfully ran 5 jobs. |
| snowpatch_ozlabs/github-powerpc_kernel_qemu | success | Successfully ran 21 jobs. |
On Fri, Sep 20, 2024 at 05:47:40PM +0000, Colton Lewis wrote: > 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> This looks good to me, though I wonder if we should handle all of the exclude_* flags in one go and pick the right user/kernel/guest regs to sample from... As this stands, it's definitely an improvement on what we have, so: Acked-by: Mark Rutland <mark.rutland@arm.com> Mark. > --- > arch/arm64/include/asm/perf_event.h | 4 ---- > arch/arm64/kernel/perf_callchain.c | 28 ---------------------------- > arch/x86/events/core.c | 16 ++++------------ > include/linux/perf_event.h | 21 +++++++++++++++++++-- > kernel/events/core.c | 21 +++++++++++++++++---- > 5 files changed, 40 insertions(+), 50 deletions(-) > > diff --git a/arch/arm64/include/asm/perf_event.h b/arch/arm64/include/asm/perf_event.h > index 31a5584ed423..ee45b4e77347 100644 > --- a/arch/arm64/include/asm/perf_event.h > +++ b/arch/arm64/include/asm/perf_event.h > @@ -10,10 +10,6 @@ > #include <asm/ptrace.h> > > #ifdef CONFIG_PERF_EVENTS > -struct pt_regs; > -extern unsigned long perf_arch_instruction_pointer(struct pt_regs *regs); > -extern unsigned long perf_arch_misc_flags(struct pt_regs *regs); > -#define perf_arch_misc_flags(regs) perf_misc_flags(regs) > #define perf_arch_bpf_user_pt_regs(regs) ®s->user_regs > #endif > > diff --git a/arch/arm64/kernel/perf_callchain.c b/arch/arm64/kernel/perf_callchain.c > index 01a9d08fc009..9b7f26b128b5 100644 > --- a/arch/arm64/kernel/perf_callchain.c > +++ b/arch/arm64/kernel/perf_callchain.c > @@ -38,31 +38,3 @@ void perf_callchain_kernel(struct perf_callchain_entry_ctx *entry, > > arch_stack_walk(callchain_trace, entry, current, regs); > } > - > -unsigned long perf_arch_instruction_pointer(struct pt_regs *regs) > -{ > - if (perf_guest_state()) > - return perf_guest_get_ip(); > - > - return instruction_pointer(regs); > -} > - > -unsigned long perf_arch_misc_flags(struct pt_regs *regs) > -{ > - unsigned int guest_state = perf_guest_state(); > - int misc = 0; > - > - if (guest_state) { > - if (guest_state & PERF_GUEST_USER) > - misc |= PERF_RECORD_MISC_GUEST_USER; > - else > - misc |= PERF_RECORD_MISC_GUEST_KERNEL; > - } else { > - if (user_mode(regs)) > - misc |= PERF_RECORD_MISC_USER; > - else > - misc |= PERF_RECORD_MISC_KERNEL; > - } > - > - return misc; > -} > diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c > index d51e5d24802b..3c5f512d2bcf 100644 > --- a/arch/x86/events/core.c > +++ b/arch/x86/events/core.c > @@ -2942,9 +2942,6 @@ static unsigned long code_segment_base(struct pt_regs *regs) > > unsigned long perf_arch_instruction_pointer(struct pt_regs *regs) > { > - if (perf_guest_state()) > - return perf_guest_get_ip(); > - > return regs->ip + code_segment_base(regs); > } > > @@ -2971,17 +2968,12 @@ unsigned long perf_arch_guest_misc_flags(struct pt_regs *regs) > > unsigned long perf_arch_misc_flags(struct pt_regs *regs) > { > - unsigned int guest_state = perf_guest_state(); > unsigned long misc = common_misc_flags(regs); > > - if (guest_state) { > - misc |= perf_arch_guest_misc_flags(regs); > - } else { > - if (user_mode(regs)) > - misc |= PERF_RECORD_MISC_USER; > - else > - misc |= PERF_RECORD_MISC_KERNEL; > - } > + if (user_mode(regs)) > + misc |= PERF_RECORD_MISC_USER; > + else > + misc |= PERF_RECORD_MISC_KERNEL; > > return misc; > } > diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h > index d061e327ad54..968f3edd95e4 100644 > --- a/include/linux/perf_event.h > +++ b/include/linux/perf_event.h > @@ -1633,8 +1633,9 @@ extern void perf_tp_event(u16 event_type, u64 count, void *record, > struct task_struct *task); > extern void perf_bp_event(struct perf_event *event, void *data); > > -extern unsigned long perf_misc_flags(struct pt_regs *regs); > -extern unsigned long perf_instruction_pointer(struct pt_regs *regs); > +extern unsigned long perf_misc_flags(struct perf_event *event, struct pt_regs *regs); > +extern unsigned long perf_instruction_pointer(struct perf_event *event, > + struct pt_regs *regs); > > #ifndef perf_arch_misc_flags > # define perf_arch_misc_flags(regs) \ > @@ -1645,6 +1646,22 @@ extern unsigned long perf_instruction_pointer(struct pt_regs *regs); > # define perf_arch_bpf_user_pt_regs(regs) regs > #endif > > +#ifndef perf_arch_guest_misc_flags > +static inline unsigned long perf_arch_guest_misc_flags(struct pt_regs *regs) > +{ > + unsigned long guest_state = perf_guest_state(); > + > + if (guest_state & PERF_GUEST_USER) > + return PERF_RECORD_MISC_GUEST_USER; > + > + if (guest_state & PERF_GUEST_ACTIVE) > + return PERF_RECORD_MISC_GUEST_KERNEL; > + > + return 0; > +} > +# define perf_arch_guest_misc_flags(regs) perf_arch_guest_misc_flags(regs) > +#endif > + > static inline bool has_branch_stack(struct perf_event *event) > { > return event->attr.sample_type & PERF_SAMPLE_BRANCH_STACK; > diff --git a/kernel/events/core.c b/kernel/events/core.c > index eeabbf791a8c..c5e57c024d9a 100644 > --- a/kernel/events/core.c > +++ b/kernel/events/core.c > @@ -6921,13 +6921,26 @@ void perf_unregister_guest_info_callbacks(struct perf_guest_info_callbacks *cbs) > EXPORT_SYMBOL_GPL(perf_unregister_guest_info_callbacks); > #endif > > -unsigned long perf_misc_flags(struct pt_regs *regs) > +static bool should_sample_guest(struct perf_event *event) > { > + return !event->attr.exclude_guest && perf_guest_state(); > +} > + > +unsigned long perf_misc_flags(struct perf_event *event, > + struct pt_regs *regs) > +{ > + if (should_sample_guest(event)) > + return perf_arch_guest_misc_flags(regs); > + > return perf_arch_misc_flags(regs); > } > > -unsigned long perf_instruction_pointer(struct pt_regs *regs) > +unsigned long perf_instruction_pointer(struct perf_event *event, > + struct pt_regs *regs) > { > + if (should_sample_guest(event)) > + return perf_guest_get_ip(); > + > return perf_arch_instruction_pointer(regs); > } > > @@ -7743,7 +7756,7 @@ void perf_prepare_sample(struct perf_sample_data *data, > __perf_event_header__init_id(data, event, filtered_sample_type); > > if (filtered_sample_type & PERF_SAMPLE_IP) { > - data->ip = perf_instruction_pointer(regs); > + data->ip = perf_instruction_pointer(event, regs); > data->sample_flags |= PERF_SAMPLE_IP; > } > > @@ -7907,7 +7920,7 @@ void perf_prepare_header(struct perf_event_header *header, > { > header->type = PERF_RECORD_SAMPLE; > header->size = perf_sample_data_size(data, event); > - header->misc = perf_misc_flags(regs); > + header->misc = perf_misc_flags(event, regs); > > /* > * If you're adding more sample types here, you likely need to do > -- > 2.46.0.792.g87dc391469-goog >
diff --git a/arch/arm64/include/asm/perf_event.h b/arch/arm64/include/asm/perf_event.h index 31a5584ed423..ee45b4e77347 100644 --- a/arch/arm64/include/asm/perf_event.h +++ b/arch/arm64/include/asm/perf_event.h @@ -10,10 +10,6 @@ #include <asm/ptrace.h> #ifdef CONFIG_PERF_EVENTS -struct pt_regs; -extern unsigned long perf_arch_instruction_pointer(struct pt_regs *regs); -extern unsigned long perf_arch_misc_flags(struct pt_regs *regs); -#define perf_arch_misc_flags(regs) perf_misc_flags(regs) #define perf_arch_bpf_user_pt_regs(regs) ®s->user_regs #endif diff --git a/arch/arm64/kernel/perf_callchain.c b/arch/arm64/kernel/perf_callchain.c index 01a9d08fc009..9b7f26b128b5 100644 --- a/arch/arm64/kernel/perf_callchain.c +++ b/arch/arm64/kernel/perf_callchain.c @@ -38,31 +38,3 @@ void perf_callchain_kernel(struct perf_callchain_entry_ctx *entry, arch_stack_walk(callchain_trace, entry, current, regs); } - -unsigned long perf_arch_instruction_pointer(struct pt_regs *regs) -{ - if (perf_guest_state()) - return perf_guest_get_ip(); - - return instruction_pointer(regs); -} - -unsigned long perf_arch_misc_flags(struct pt_regs *regs) -{ - unsigned int guest_state = perf_guest_state(); - int misc = 0; - - if (guest_state) { - if (guest_state & PERF_GUEST_USER) - misc |= PERF_RECORD_MISC_GUEST_USER; - else - misc |= PERF_RECORD_MISC_GUEST_KERNEL; - } else { - if (user_mode(regs)) - misc |= PERF_RECORD_MISC_USER; - else - misc |= PERF_RECORD_MISC_KERNEL; - } - - return misc; -} diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c index d51e5d24802b..3c5f512d2bcf 100644 --- a/arch/x86/events/core.c +++ b/arch/x86/events/core.c @@ -2942,9 +2942,6 @@ static unsigned long code_segment_base(struct pt_regs *regs) unsigned long perf_arch_instruction_pointer(struct pt_regs *regs) { - if (perf_guest_state()) - return perf_guest_get_ip(); - return regs->ip + code_segment_base(regs); } @@ -2971,17 +2968,12 @@ unsigned long perf_arch_guest_misc_flags(struct pt_regs *regs) unsigned long perf_arch_misc_flags(struct pt_regs *regs) { - unsigned int guest_state = perf_guest_state(); unsigned long misc = common_misc_flags(regs); - if (guest_state) { - misc |= perf_arch_guest_misc_flags(regs); - } else { - if (user_mode(regs)) - misc |= PERF_RECORD_MISC_USER; - else - misc |= PERF_RECORD_MISC_KERNEL; - } + if (user_mode(regs)) + misc |= PERF_RECORD_MISC_USER; + else + misc |= PERF_RECORD_MISC_KERNEL; return misc; } diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index d061e327ad54..968f3edd95e4 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -1633,8 +1633,9 @@ extern void perf_tp_event(u16 event_type, u64 count, void *record, struct task_struct *task); extern void perf_bp_event(struct perf_event *event, void *data); -extern unsigned long perf_misc_flags(struct pt_regs *regs); -extern unsigned long perf_instruction_pointer(struct pt_regs *regs); +extern unsigned long perf_misc_flags(struct perf_event *event, struct pt_regs *regs); +extern unsigned long perf_instruction_pointer(struct perf_event *event, + struct pt_regs *regs); #ifndef perf_arch_misc_flags # define perf_arch_misc_flags(regs) \ @@ -1645,6 +1646,22 @@ extern unsigned long perf_instruction_pointer(struct pt_regs *regs); # define perf_arch_bpf_user_pt_regs(regs) regs #endif +#ifndef perf_arch_guest_misc_flags +static inline unsigned long perf_arch_guest_misc_flags(struct pt_regs *regs) +{ + unsigned long guest_state = perf_guest_state(); + + if (guest_state & PERF_GUEST_USER) + return PERF_RECORD_MISC_GUEST_USER; + + if (guest_state & PERF_GUEST_ACTIVE) + return PERF_RECORD_MISC_GUEST_KERNEL; + + return 0; +} +# define perf_arch_guest_misc_flags(regs) perf_arch_guest_misc_flags(regs) +#endif + static inline bool has_branch_stack(struct perf_event *event) { return event->attr.sample_type & PERF_SAMPLE_BRANCH_STACK; diff --git a/kernel/events/core.c b/kernel/events/core.c index eeabbf791a8c..c5e57c024d9a 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -6921,13 +6921,26 @@ void perf_unregister_guest_info_callbacks(struct perf_guest_info_callbacks *cbs) EXPORT_SYMBOL_GPL(perf_unregister_guest_info_callbacks); #endif -unsigned long perf_misc_flags(struct pt_regs *regs) +static bool should_sample_guest(struct perf_event *event) { + return !event->attr.exclude_guest && perf_guest_state(); +} + +unsigned long perf_misc_flags(struct perf_event *event, + struct pt_regs *regs) +{ + if (should_sample_guest(event)) + return perf_arch_guest_misc_flags(regs); + return perf_arch_misc_flags(regs); } -unsigned long perf_instruction_pointer(struct pt_regs *regs) +unsigned long perf_instruction_pointer(struct perf_event *event, + struct pt_regs *regs) { + if (should_sample_guest(event)) + return perf_guest_get_ip(); + return perf_arch_instruction_pointer(regs); } @@ -7743,7 +7756,7 @@ void perf_prepare_sample(struct perf_sample_data *data, __perf_event_header__init_id(data, event, filtered_sample_type); if (filtered_sample_type & PERF_SAMPLE_IP) { - data->ip = perf_instruction_pointer(regs); + data->ip = perf_instruction_pointer(event, regs); data->sample_flags |= PERF_SAMPLE_IP; } @@ -7907,7 +7920,7 @@ void perf_prepare_header(struct perf_event_header *header, { header->type = PERF_RECORD_SAMPLE; header->size = perf_sample_data_size(data, event); - header->misc = perf_misc_flags(regs); + header->misc = perf_misc_flags(event, regs); /* * If you're adding more sample types here, you likely need to do
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> --- arch/arm64/include/asm/perf_event.h | 4 ---- arch/arm64/kernel/perf_callchain.c | 28 ---------------------------- arch/x86/events/core.c | 16 ++++------------ include/linux/perf_event.h | 21 +++++++++++++++++++-- kernel/events/core.c | 21 +++++++++++++++++---- 5 files changed, 40 insertions(+), 50 deletions(-)