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Message-ID: <7bacbe72-c283-453b-bf1f-6ba05b68cac8@intel.com>
Date: Wed, 30 Oct 2024 15:16:00 +0200
From: Adrian Hunter <adrian.hunter@...el.com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: Ingo Molnar <mingo@...hat.com>, Mark Rutland <mark.rutland@....com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Heiko Carstens <hca@...ux.ibm.com>, Thomas Richter <tmricht@...ux.ibm.com>,
Hendrik Brueckner <brueckner@...ux.ibm.com>,
Suzuki K Poulose <suzuki.poulose@....com>, Mike Leach
<mike.leach@...aro.org>, James Clark <james.clark@....com>,
coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org,
Yicong Yang <yangyicong@...ilicon.com>,
Jonathan Cameron <jonathan.cameron@...wei.com>, Will Deacon
<will@...nel.org>, Arnaldo Carvalho de Melo <acme@...nel.org>,
Jiri Olsa <jolsa@...nel.org>, Namhyung Kim <namhyung@...nel.org>,
Ian Rogers <irogers@...gle.com>, Andi Kleen <ak@...ux.intel.com>,
Thomas Gleixner <tglx@...utronix.de>, Borislav Petkov <bp@...en8.de>,
Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
H Peter Anvin <hpa@...or.com>, Kan Liang <kan.liang@...ux.intel.com>,
linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org
Subject: Re: [PATCH V14 00/11] perf/core: Add ability for an event to "pause"
or "resume" AUX area tracing
On 22/10/24 18:59, Adrian Hunter wrote:
> Hi
>
> Note for V14:
> KVM patches dropped.
ping
>
> Note for V12:
> There was a small conflict between the Intel PT changes in
> "KVM: x86: Fix Intel PT Host/Guest mode when host tracing" and the
> changes in this patch set, so I have put the patch sets together,
> along with outstanding fix "perf/x86/intel/pt: Fix buffer full but
> size is 0 case"
>
> Cover letter for KVM changes (patches 2 to 4):
>
> There is a long-standing problem whereby running Intel PT on host and guest
> in Host/Guest mode, causes VM-Entry failure.
>
> The motivation for this patch set is to provide a fix for stable kernels
> prior to the advent of the "Mediated Passthrough vPMU" patch set:
>
> https://lore.kernel.org/kvm/20240801045907.4010984-1-mizhang@google.com/
>
> which would render a large part of the fix unnecessary but likely not be
> suitable for backport to stable due to its size and complexity.
>
> Ideally, this patch set would be applied before "Mediated Passthrough vPMU"
>
> Note that the fix does not conflict with "Mediated Passthrough vPMU", it
> is just that "Mediated Passthrough vPMU" will make the code to stop and
> restart Intel PT unnecessary.
>
> Note for V11:
> Moving aux_paused into a union within struct hw_perf_event caused
> a regression because aux_paused was being written unconditionally
> even though it is valid only for AUX (e.g. Intel PT) PMUs.
> That is fixed in V11.
>
> Hardware traces, such as instruction traces, can produce a vast amount of
> trace data, so being able to reduce tracing to more specific circumstances
> can be useful.
>
> The ability to pause or resume tracing when another event happens, can do
> that.
>
> These patches add such a facilty and show how it would work for Intel
> Processor Trace.
>
> Maintainers of other AUX area tracing implementations are requested to
> consider if this is something they might employ and then whether or not
> the ABI would work for them. Note, thank you to James Clark (ARM) for
> evaluating the API for Coresight. Suzuki K Poulose (ARM) also responded
> positively to the RFC.
>
> Changes to perf tools are now (since V4) fleshed out.
>
> Please note, Intel® Architecture Instruction Set Extensions and Future
> Features Programming Reference March 2024 319433-052, currently:
>
> https://cdrdv2.intel.com/v1/dl/getContent/671368
>
> introduces hardware pause / resume for Intel PT in a feature named
> Intel PT Trigger Tracing.
>
> For that more fields in perf_event_attr will be necessary. The main
> differences are:
> - it can be applied not just to overflows, but optionally to
> every event
> - a packet is emitted into the trace, optionally with IP
> information
> - no PMI
> - works with PMC and DR (breakpoint) events only
>
> Here are the proposed additions to perf_event_attr, please comment:
>
> diff --git a/tools/include/uapi/linux/perf_event.h b/tools/include/uapi/linux/perf_event.h
> index 0c557f0a17b3..05dcc43f11bb 100644
> --- a/tools/include/uapi/linux/perf_event.h
> +++ b/tools/include/uapi/linux/perf_event.h
> @@ -369,6 +369,22 @@ enum perf_event_read_format {
> PERF_FORMAT_MAX = 1U << 5, /* non-ABI */
> };
>
> +enum {
> + PERF_AUX_ACTION_START_PAUSED = 1U << 0,
> + PERF_AUX_ACTION_PAUSE = 1U << 1,
> + PERF_AUX_ACTION_RESUME = 1U << 2,
> + PERF_AUX_ACTION_EMIT = 1U << 3,
> + PERF_AUX_ACTION_NR = 0x1f << 4,
> + PERF_AUX_ACTION_NO_IP = 1U << 9,
> + PERF_AUX_ACTION_PAUSE_ON_EVT = 1U << 10,
> + PERF_AUX_ACTION_RESUME_ON_EVT = 1U << 11,
> + PERF_AUX_ACTION_EMIT_ON_EVT = 1U << 12,
> + PERF_AUX_ACTION_NR_ON_EVT = 0x1f << 13,
> + PERF_AUX_ACTION_NO_IP_ON_EVT = 1U << 18,
> + PERF_AUX_ACTION_MASK = ~PERF_AUX_ACTION_START_PAUSED,
> + PERF_AUX_PAUSE_RESUME_MASK = PERF_AUX_ACTION_PAUSE | PERF_AUX_ACTION_RESUME,
> +};
> +
> #define PERF_ATTR_SIZE_VER0 64 /* sizeof first published struct */
> #define PERF_ATTR_SIZE_VER1 72 /* add: config2 */
> #define PERF_ATTR_SIZE_VER2 80 /* add: branch_sample_type */
> @@ -515,10 +531,19 @@ struct perf_event_attr {
> union {
> __u32 aux_action;
> struct {
> - __u32 aux_start_paused : 1, /* start AUX area tracing paused */
> - aux_pause : 1, /* on overflow, pause AUX area tracing */
> - aux_resume : 1, /* on overflow, resume AUX area tracing */
> - __reserved_3 : 29;
> + __u32 aux_start_paused : 1, /* start AUX area tracing paused */
> + aux_pause : 1, /* on overflow, pause AUX area tracing */
> + aux_resume : 1, /* on overflow, resume AUX area tracing */
> + aux_emit : 1, /* generate AUX records instead of events */
> + aux_nr : 5, /* AUX area tracing reference number */
> + aux_no_ip : 1, /* suppress IP in AUX records */
> + /* Following apply to event occurrence not overflows */
> + aux_pause_on_evt : 1, /* on event, pause AUX area tracing */
> + aux_resume_on_evt : 1, /* on event, resume AUX area tracing */
> + aux_emit_on_evt : 1, /* generate AUX records instead of events */
> + aux_nr_on_evt : 5, /* AUX area tracing reference number */
> + aux_no_ip_on_evt : 1, /* suppress IP in AUX records */
> + __reserved_3 : 13;
> };
> };
>
>
> Changes in V14:
> Dropped KVM patches
>
> perf/x86/intel/pt: Add support for pause / resume
> Set pt->handle_nmi after configuration is completed instead of during
>
> Changes in V13:
> perf/core: Add aux_pause, aux_resume, aux_start_paused
> Do aux_resume at the end of __perf_event_overflow() so as to trace
> less of perf itself
>
> perf tools: Add missing_features for aux_start_paused, aux_pause, aux_resume
> Add error message also in EOPNOTSUPP case (Leo)
>
> Changes in V12:
> Add previously sent patch "perf/x86/intel/pt: Fix buffer full
> but size is 0 case"
>
> Add previously sent patch set "KVM: x86: Fix Intel PT Host/Guest
> mode when host tracing"
>
> Rebase on current tip plus patch set "KVM: x86: Fix Intel PT Host/Guest
> mode when host tracing"
>
> Changes in V11:
> perf/core: Add aux_pause, aux_resume, aux_start_paused
> Make assignment to event->hw.aux_paused conditional on
> (pmu->capabilities & PERF_PMU_CAP_AUX_PAUSE).
>
> perf/x86/intel: Do not enable large PEBS for events with aux actions or aux sampling
> Remove definition of has_aux_action() because it has
> already been added as an inline function.
>
> perf/x86/intel/pt: Fix sampling synchronization
> perf tools: Enable evsel__is_aux_event() to work for ARM/ARM64
> perf tools: Enable evsel__is_aux_event() to work for S390_CPUMSF
> Dropped because they have already been applied
>
> Changes in V10:
> perf/core: Add aux_pause, aux_resume, aux_start_paused
> Move aux_paused into a union within struct hw_perf_event.
> Additional comment wrt PERF_EF_PAUSE/PERF_EF_RESUME.
> Factor out has_aux_action() as an inline function.
> Use scoped_guard for irqsave.
> Move calls of perf_event_aux_pause() from __perf_event_output()
> to __perf_event_overflow().
>
> Changes in V9:
> perf/x86/intel/pt: Fix sampling synchronization
> New patch
>
> perf/core: Add aux_pause, aux_resume, aux_start_paused
> Move aux_paused to struct hw_perf_event
>
> perf/x86/intel/pt: Add support for pause / resume
> Add more comments and barriers for resume_allowed and
> pause_allowed
> Always use WRITE_ONCE with resume_allowed
>
>
> Changes in V8:
>
> perf tools: Parse aux-action
> Fix clang warning:
> util/auxtrace.c:821:7: error: missing field 'aux_action' initializer [-Werror,-Wmissing-field-initializers]
> 821 | {NULL},
> | ^
>
> Changes in V7:
>
> Add Andi's Reviewed-by for patches 2-12
> Re-base
>
> Changes in V6:
>
> perf/core: Add aux_pause, aux_resume, aux_start_paused
> Removed READ/WRITE_ONCE from __perf_event_aux_pause()
> Expanded comment about guarding against NMI
>
> Changes in V5:
>
> perf/core: Add aux_pause, aux_resume, aux_start_paused
> Added James' Ack
>
> perf/x86/intel: Do not enable large PEBS for events with aux actions or aux sampling
> New patch
>
> perf tools
> Added Ian's Ack
>
> Changes in V4:
>
> perf/core: Add aux_pause, aux_resume, aux_start_paused
> Rename aux_output_cfg -> aux_action
> Reorder aux_action bits from:
> aux_pause, aux_resume, aux_start_paused
> to:
> aux_start_paused, aux_pause, aux_resume
> Fix aux_action bits __u64 -> __u32
>
> coresight: Have a stab at support for pause / resume
> Dropped
>
> perf tools
> All new patches
>
> Changes in RFC V3:
>
> coresight: Have a stab at support for pause / resume
> 'mode' -> 'flags' so it at least compiles
>
> Changes in RFC V2:
>
> Use ->stop() / ->start() instead of ->pause_resume()
> Move aux_start_paused bit into aux_output_cfg
> Tighten up when Intel PT pause / resume is allowed
> Add an example of how it might work for CoreSight
>
>
> Adrian Hunter (11):
> perf/x86/intel/pt: Fix buffer full but size is 0 case
> perf/core: Add aux_pause, aux_resume, aux_start_paused
> perf/x86/intel/pt: Add support for pause / resume
> perf/x86/intel: Do not enable large PEBS for events with aux actions or aux sampling
> perf tools: Add aux_start_paused, aux_pause and aux_resume
> perf tools: Add aux-action config term
> perf tools: Parse aux-action
> perf tools: Add missing_features for aux_start_paused, aux_pause, aux_resume
> perf intel-pt: Improve man page format
> perf intel-pt: Add documentation for pause / resume
> perf intel-pt: Add a test for pause / resume
>
> arch/x86/events/intel/core.c | 4 +-
> arch/x86/events/intel/pt.c | 84 +++-
> arch/x86/events/intel/pt.h | 6 +
> include/linux/perf_event.h | 28 ++
> include/uapi/linux/perf_event.h | 11 +-
> kernel/events/core.c | 75 +++-
> kernel/events/internal.h | 1 +
> tools/include/uapi/linux/perf_event.h | 11 +-
> tools/perf/Documentation/perf-intel-pt.txt | 596 ++++++++++++++++++-----------
> tools/perf/Documentation/perf-record.txt | 4 +
> tools/perf/builtin-record.c | 4 +-
> tools/perf/tests/shell/test_intel_pt.sh | 28 ++
> tools/perf/util/auxtrace.c | 67 +++-
> tools/perf/util/auxtrace.h | 6 +-
> tools/perf/util/evsel.c | 15 +
> tools/perf/util/evsel.h | 1 +
> tools/perf/util/evsel_config.h | 1 +
> tools/perf/util/parse-events.c | 10 +
> tools/perf/util/parse-events.h | 1 +
> tools/perf/util/parse-events.l | 1 +
> tools/perf/util/perf_event_attr_fprintf.c | 3 +
> tools/perf/util/pmu.c | 1 +
> 22 files changed, 716 insertions(+), 242 deletions(-)
>
>
> Regards
> Adrian
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