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Message-ID: <a17cff0a-44d4-5d36-f08f-82d304b217bc@intel.com>
Date:   Thu, 11 Aug 2022 20:19:36 +0300
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Subject: Re: [PATCH 24/35] perf inject: Add support for injecting guest
 sideband events
Content-Language: en-US
To:     Ian Rogers <irogers@google.com>
Cc:     Arnaldo Carvalho de Melo <acme@kernel.org>,
        Jiri Olsa <jolsa@redhat.com>,
        Namhyung Kim <namhyung@kernel.org>,
        Andi Kleen <ak@linux.intel.com>, linux-kernel@vger.kernel.org,
        kvm@vger.kernel.org
References: <20220711093218.10967-1-adrian.hunter@intel.com>
 <20220711093218.10967-25-adrian.hunter@intel.com>
 <CAP-5=fXTHWoY-LudTnKDGCMRN61zyvSMtORduUjJ_eXgpai8BA@mail.gmail.com>
From:   Adrian Hunter <adrian.hunter@intel.com>
Organization: Intel Finland Oy, Registered Address: PL 281, 00181 Helsinki,
 Business Identity Code: 0357606 - 4, Domiciled in Helsinki
In-Reply-To: <CAP-5=fXTHWoY-LudTnKDGCMRN61zyvSMtORduUjJ_eXgpai8BA@mail.gmail.com>
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On 20/07/22 04:06, Ian Rogers wrote:
> On Mon, Jul 11, 2022 at 2:33 AM Adrian Hunter <adrian.hunter@intel.com> wrote:
>>
>> Inject events from a perf.data file recorded in a virtual machine into
>> a perf.data file recorded on the host at the same time.
>>
>> Only side band events (e.g. mmap, comm, fork, exit etc) and build IDs are
>> injected.  Additionally, the guest kcore_dir is copied as kcore_dir__
>> appended to the machine PID.
>>
>> This is non-trivial because:
>>  o It is not possible to process 2 sessions simultaneously so instead
>>  events are first written to a temporary file.
>>  o To avoid conflict, guest sample IDs are replaced with new unused sample
>>  IDs.
>>  o Guest event's CPU is changed to be the host CPU because it is more
>>  useful for reporting and analysis.
>>  o Sample ID is mapped to machine PID which is recorded with VCPU in the
>>  id index. This is important to allow guest events to be related to the
>>  guest machine and VCPU.
>>  o Timestamps must be converted.
>>  o Events are inserted to obey finished-round ordering.
>>
>> The anticipated use-case is:
>>  - start recording sideband events in a guest machine
>>  - start recording an AUX area trace on the host which can trace also the
>>  guest (e.g. Intel PT)
>>  - run test case on the guest
>>  - stop recording on the host
>>  - stop recording on the guest
>>  - copy the guest perf.data file to the host
>>  - inject the guest perf.data file sideband events into the host perf.data
>>  file using perf inject
>>  - the resulting perf.data file can now be used
>>
>> Subsequent patches provide Intel PT support for this.
>>
>> Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
>> ---
>>  tools/perf/Documentation/perf-inject.txt |   17 +
>>  tools/perf/builtin-inject.c              | 1043 +++++++++++++++++++++-
>>  2 files changed, 1059 insertions(+), 1 deletion(-)
>>
>> diff --git a/tools/perf/Documentation/perf-inject.txt b/tools/perf/Documentation/perf-inject.txt
>> index 0570a1ccd344..646aa31586ed 100644
>> --- a/tools/perf/Documentation/perf-inject.txt
>> +++ b/tools/perf/Documentation/perf-inject.txt
>> @@ -85,6 +85,23 @@ include::itrace.txt[]
>>         without updating it. Currently this option is supported only by
>>         Intel PT, refer linkperf:perf-intel-pt[1]
>>
>> +--guest-data=<path>,<pid>[,<time offset>[,<time scale>]]::
>> +       Insert events from a perf.data file recorded in a virtual machine at
>> +       the same time as the input perf.data file was recorded on the host.
>> +       The Process ID (PID) of the QEMU hypervisor process must be provided,
>> +       and the time offset and time scale (multiplier) will likely be needed
>> +       to convert guest time stamps into host time stamps. For example, for
>> +       x86 the TSC Offset and Multiplier could be provided for a virtual machine
>> +       using Linux command line option no-kvmclock.
>> +       Currently only mmap, mmap2, comm, task, context_switch, ksymbol,
>> +       and text_poke events are inserted, as well as build ID information.
>> +       The QEMU option -name debug-threads=on is needed so that thread names
>> +       can be used to determine which thread is running which VCPU. Note
>> +       libvirt seems to use this by default.
>> +       When using perf record in the guest, option --sample-identifier
>> +       should be used, and also --buildid-all and --switch-events may be
>> +       useful.
>> +
> 
> Would other hypervisors based on kvm like gVisor work if they
> implemented name-debug-threads?

AFAICT gVisor is not a machine level hypervisor so the issue does not arise.

> 
>>  SEE ALSO
>>  --------
>>  linkperf:perf-record[1], linkperf:perf-report[1], linkperf:perf-archive[1],
>> diff --git a/tools/perf/builtin-inject.c b/tools/perf/builtin-inject.c
>> index c800911f68e7..fd4547bb75f7 100644
>> --- a/tools/perf/builtin-inject.c
>> +++ b/tools/perf/builtin-inject.c
>> @@ -26,6 +26,7 @@
>>  #include "util/thread.h"
>>  #include "util/namespaces.h"
>>  #include "util/util.h"
>> +#include "util/tsc.h"
>>
>>  #include <internal/lib.h>
>>
>> @@ -35,8 +36,70 @@
>>
>>  #include <linux/list.h>
>>  #include <linux/string.h>
>> +#include <linux/zalloc.h>
>> +#include <linux/hash.h>
>>  #include <errno.h>
>>  #include <signal.h>
>> +#include <inttypes.h>
>> +
>> +struct guest_event {
>> +       struct perf_sample              sample;
>> +       union perf_event                *event;
>> +       char                            event_buf[PERF_SAMPLE_MAX_SIZE];
>> +};
>> +
>> +struct guest_id {
>> +       /* hlist_node must be first, see free_hlist() */
>> +       struct hlist_node               node;
>> +       u64                             id;
>> +       u64                             host_id;
>> +       u32                             vcpu;
>> +};
>> +
>> +struct guest_tid {
>> +       /* hlist_node must be first, see free_hlist() */
>> +       struct hlist_node               node;
>> +       /* Thread ID of QEMU thread */
>> +       u32                             tid;
>> +       u32                             vcpu;
>> +};
>> +
>> +struct guest_vcpu {
>> +       /* Current host CPU */
>> +       u32                             cpu;
>> +       /* Thread ID of QEMU thread */
>> +       u32                             tid;
>> +};
>> +
>> +struct guest_session {
>> +       char                            *perf_data_file;
>> +       u32                             machine_pid;
>> +       u64                             time_offset;
>> +       double                          time_scale;
>> +       struct perf_tool                tool;
>> +       struct perf_data                data;
>> +       struct perf_session             *session;
>> +       char                            *tmp_file_name;
>> +       int                             tmp_fd;
>> +       struct perf_tsc_conversion      host_tc;
>> +       struct perf_tsc_conversion      guest_tc;
>> +       bool                            copy_kcore_dir;
>> +       bool                            have_tc;
>> +       bool                            fetched;
>> +       bool                            ready;
>> +       u16                             dflt_id_hdr_size;
>> +       u64                             dflt_id;
>> +       u64                             highest_id;
>> +       /* Array of guest_vcpu */
>> +       struct guest_vcpu               *vcpu;
>> +       size_t                          vcpu_cnt;
>> +       /* Hash table for guest_id */
>> +       struct hlist_head               heads[PERF_EVLIST__HLIST_SIZE];
>> +       /* Hash table for guest_tid */
>> +       struct hlist_head               tids[PERF_EVLIST__HLIST_SIZE];
>> +       /* Place to stash next guest event */
>> +       struct guest_event              ev;
>> +};
>>
>>  struct perf_inject {
>>         struct perf_tool        tool;
>> @@ -59,6 +122,7 @@ struct perf_inject {
>>         struct itrace_synth_opts itrace_synth_opts;
>>         char                    event_copy[PERF_SAMPLE_MAX_SIZE];
>>         struct perf_file_section secs[HEADER_FEAT_BITS];
>> +       struct guest_session    guest_session;
>>  };
>>
>>  struct event_entry {
>> @@ -698,6 +762,841 @@ static int perf_inject__sched_stat(struct perf_tool *tool,
>>         return perf_event__repipe(tool, event_sw, &sample_sw, machine);
>>  }
>>
>> +static struct guest_vcpu *guest_session__vcpu(struct guest_session *gs, u32 vcpu)
>> +{
>> +       if (realloc_array_as_needed(gs->vcpu, gs->vcpu_cnt, vcpu, NULL))
>> +               return NULL;
>> +       return &gs->vcpu[vcpu];
>> +}
>> +
>> +static int guest_session__output_bytes(struct guest_session *gs, void *buf, size_t sz)
>> +{
>> +       ssize_t ret = writen(gs->tmp_fd, buf, sz);
>> +
>> +       return ret < 0 ? ret : 0;
>> +}
>> +
>> +static int guest_session__repipe(struct perf_tool *tool,
>> +                                union perf_event *event,
>> +                                struct perf_sample *sample __maybe_unused,
>> +                                struct machine *machine __maybe_unused)
>> +{
>> +       struct guest_session *gs = container_of(tool, struct guest_session, tool);
>> +
>> +       return guest_session__output_bytes(gs, event, event->header.size);
>> +}
>> +
>> +static int guest_session__map_tid(struct guest_session *gs, u32 tid, u32 vcpu)
>> +{
>> +       struct guest_tid *guest_tid = zalloc(sizeof(*guest_tid));
>> +       int hash;
>> +
>> +       if (!guest_tid)
>> +               return -ENOMEM;
>> +
>> +       guest_tid->tid = tid;
>> +       guest_tid->vcpu = vcpu;
>> +       hash = hash_32(guest_tid->tid, PERF_EVLIST__HLIST_BITS);
>> +       hlist_add_head(&guest_tid->node, &gs->tids[hash]);
>> +
>> +       return 0;
>> +}
>> +
>> +static int host_peek_vm_comms_cb(struct perf_session *session __maybe_unused,
>> +                                union perf_event *event,
>> +                                u64 offset __maybe_unused, void *data)
>> +{
>> +       struct guest_session *gs = data;
>> +       unsigned int vcpu;
>> +       struct guest_vcpu *guest_vcpu;
>> +       int ret;
>> +
>> +       if (event->header.type != PERF_RECORD_COMM ||
>> +           event->comm.pid != gs->machine_pid)
>> +               return 0;
>> +
>> +       /*
>> +        * QEMU option -name debug-threads=on, causes thread names formatted as
>> +        * below, although it is not an ABI. Also libvirt seems to use this by
>> +        * default. Here we rely on it to tell us which thread is which VCPU.
>> +        */
>> +       ret = sscanf(event->comm.comm, "CPU %u/KVM", &vcpu);
>> +       if (ret <= 0)
>> +               return ret;
>> +       pr_debug("Found VCPU: tid %u comm %s vcpu %u\n",
>> +                event->comm.tid, event->comm.comm, vcpu);
>> +       if (vcpu > INT_MAX) {
>> +               pr_err("Invalid VCPU %u\n", vcpu);
>> +               return -EINVAL;
>> +       }
>> +       guest_vcpu = guest_session__vcpu(gs, vcpu);
>> +       if (!guest_vcpu)
>> +               return -ENOMEM;
>> +       if (guest_vcpu->tid && guest_vcpu->tid != event->comm.tid) {
>> +               pr_err("Fatal error: Two threads found with the same VCPU\n");
>> +               return -EINVAL;
>> +       }
>> +       guest_vcpu->tid = event->comm.tid;
>> +
>> +       return guest_session__map_tid(gs, event->comm.tid, vcpu);
>> +}
>> +
>> +static int host_peek_vm_comms(struct perf_session *session, struct guest_session *gs)
>> +{
>> +       return perf_session__peek_events(session, session->header.data_offset,
>> +                                        session->header.data_size,
>> +                                        host_peek_vm_comms_cb, gs);
>> +}
>> +
>> +static bool evlist__is_id_used(struct evlist *evlist, u64 id)
>> +{
>> +       return evlist__id2sid(evlist, id);
>> +}
>> +
>> +static u64 guest_session__allocate_new_id(struct guest_session *gs, struct evlist *host_evlist)
>> +{
>> +       do {
>> +               gs->highest_id += 1;
>> +       } while (!gs->highest_id || evlist__is_id_used(host_evlist, gs->highest_id));
>> +
>> +       return gs->highest_id;
>> +}
>> +
>> +static int guest_session__map_id(struct guest_session *gs, u64 id, u64 host_id, u32 vcpu)
>> +{
>> +       struct guest_id *guest_id = zalloc(sizeof(*guest_id));
>> +       int hash;
>> +
>> +       if (!guest_id)
>> +               return -ENOMEM;
>> +
>> +       guest_id->id = id;
>> +       guest_id->host_id = host_id;
>> +       guest_id->vcpu = vcpu;
>> +       hash = hash_64(guest_id->id, PERF_EVLIST__HLIST_BITS);
>> +       hlist_add_head(&guest_id->node, &gs->heads[hash]);
>> +
>> +       return 0;
>> +}
>> +
>> +static u64 evlist__find_highest_id(struct evlist *evlist)
>> +{
>> +       struct evsel *evsel;
>> +       u64 highest_id = 1;
>> +
>> +       evlist__for_each_entry(evlist, evsel) {
>> +               u32 j;
>> +
>> +               for (j = 0; j < evsel->core.ids; j++) {
>> +                       u64 id = evsel->core.id[j];
>> +
>> +                       if (id > highest_id)
>> +                               highest_id = id;
>> +               }
>> +       }
>> +
>> +       return highest_id;
>> +}
>> +
>> +static int guest_session__map_ids(struct guest_session *gs, struct evlist *host_evlist)
>> +{
>> +       struct evlist *evlist = gs->session->evlist;
>> +       struct evsel *evsel;
>> +       int ret;
>> +
>> +       evlist__for_each_entry(evlist, evsel) {
>> +               u32 j;
>> +
>> +               for (j = 0; j < evsel->core.ids; j++) {
>> +                       struct perf_sample_id *sid;
>> +                       u64 host_id;
>> +                       u64 id;
>> +
>> +                       id = evsel->core.id[j];
>> +                       sid = evlist__id2sid(evlist, id);
>> +                       if (!sid || sid->cpu.cpu == -1)
>> +                               continue;
>> +                       host_id = guest_session__allocate_new_id(gs, host_evlist);
>> +                       ret = guest_session__map_id(gs, id, host_id, sid->cpu.cpu);
>> +                       if (ret)
>> +                               return ret;
>> +               }
>> +       }
>> +
>> +       return 0;
>> +}
>> +
>> +static struct guest_id *guest_session__lookup_id(struct guest_session *gs, u64 id)
>> +{
>> +       struct hlist_head *head;
>> +       struct guest_id *guest_id;
>> +       int hash;
>> +
>> +       hash = hash_64(id, PERF_EVLIST__HLIST_BITS);
>> +       head = &gs->heads[hash];
>> +
>> +       hlist_for_each_entry(guest_id, head, node)
>> +               if (guest_id->id == id)
>> +                       return guest_id;
>> +
>> +       return NULL;
>> +}
>> +
>> +static int process_attr(struct perf_tool *tool, union perf_event *event,
>> +                       struct perf_sample *sample __maybe_unused,
>> +                       struct machine *machine __maybe_unused)
>> +{
>> +       struct perf_inject *inject = container_of(tool, struct perf_inject, tool);
>> +
>> +       return perf_event__process_attr(tool, event, &inject->session->evlist);
>> +}
>> +
>> +static int guest_session__add_attr(struct guest_session *gs, struct evsel *evsel)
>> +{
>> +       struct perf_inject *inject = container_of(gs, struct perf_inject, guest_session);
>> +       struct perf_event_attr attr = evsel->core.attr;
>> +       u64 *id_array;
>> +       u32 *vcpu_array;
>> +       int ret = -ENOMEM;
>> +       u32 i;
>> +
>> +       id_array = calloc(evsel->core.ids, sizeof(*id_array));
>> +       if (!id_array)
>> +               return -ENOMEM;
>> +
>> +       vcpu_array = calloc(evsel->core.ids, sizeof(*vcpu_array));
>> +       if (!vcpu_array)
>> +               goto out;
>> +
>> +       for (i = 0; i < evsel->core.ids; i++) {
>> +               u64 id = evsel->core.id[i];
>> +               struct guest_id *guest_id = guest_session__lookup_id(gs, id);
>> +
>> +               if (!guest_id) {
>> +                       pr_err("Failed to find guest id %"PRIu64"\n", id);
>> +                       ret = -EINVAL;
>> +                       goto out;
>> +               }
>> +               id_array[i] = guest_id->host_id;
>> +               vcpu_array[i] = guest_id->vcpu;
>> +       }
>> +
>> +       attr.sample_type |= PERF_SAMPLE_IDENTIFIER;
>> +       attr.exclude_host = 1;
>> +       attr.exclude_guest = 0;
>> +
>> +       ret = perf_event__synthesize_attr(&inject->tool, &attr, evsel->core.ids,
>> +                                         id_array, process_attr);
>> +       if (ret)
>> +               pr_err("Failed to add guest attr.\n");
>> +
>> +       for (i = 0; i < evsel->core.ids; i++) {
>> +               struct perf_sample_id *sid;
>> +               u32 vcpu = vcpu_array[i];
>> +
>> +               sid = evlist__id2sid(inject->session->evlist, id_array[i]);
>> +               /* Guest event is per-thread from the host point of view */
>> +               sid->cpu.cpu = -1;
>> +               sid->tid = gs->vcpu[vcpu].tid;
>> +               sid->machine_pid = gs->machine_pid;
>> +               sid->vcpu.cpu = vcpu;
>> +       }
>> +out:
>> +       free(vcpu_array);
>> +       free(id_array);
>> +       return ret;
>> +}
>> +
>> +static int guest_session__add_attrs(struct guest_session *gs)
>> +{
>> +       struct evlist *evlist = gs->session->evlist;
>> +       struct evsel *evsel;
>> +       int ret;
>> +
>> +       evlist__for_each_entry(evlist, evsel) {
>> +               ret = guest_session__add_attr(gs, evsel);
>> +               if (ret)
>> +                       return ret;
>> +       }
>> +
>> +       return 0;
>> +}
>> +
>> +static int synthesize_id_index(struct perf_inject *inject, size_t new_cnt)
>> +{
>> +       struct perf_session *session = inject->session;
>> +       struct evlist *evlist = session->evlist;
>> +       struct machine *machine = &session->machines.host;
>> +       size_t from = evlist->core.nr_entries - new_cnt;
>> +
>> +       return __perf_event__synthesize_id_index(&inject->tool, perf_event__repipe,
>> +                                                evlist, machine, from);
>> +}
>> +
>> +static struct guest_tid *guest_session__lookup_tid(struct guest_session *gs, u32 tid)
>> +{
>> +       struct hlist_head *head;
>> +       struct guest_tid *guest_tid;
>> +       int hash;
>> +
>> +       hash = hash_32(tid, PERF_EVLIST__HLIST_BITS);
>> +       head = &gs->tids[hash];
>> +
>> +       hlist_for_each_entry(guest_tid, head, node)
>> +               if (guest_tid->tid == tid)
>> +                       return guest_tid;
>> +
>> +       return NULL;
>> +}
>> +
>> +static bool dso__is_in_kernel_space(struct dso *dso)
>> +{
>> +       if (dso__is_vdso(dso))
>> +               return false;
>> +
>> +       return dso__is_kcore(dso) ||
>> +              dso->kernel ||
>> +              is_kernel_module(dso->long_name, PERF_RECORD_MISC_CPUMODE_UNKNOWN);
>> +}
>> +
>> +static u64 evlist__first_id(struct evlist *evlist)
>> +{
>> +       struct evsel *evsel;
>> +
>> +       evlist__for_each_entry(evlist, evsel) {
>> +               if (evsel->core.ids)
>> +                       return evsel->core.id[0];
>> +       }
>> +       return 0;
>> +}
>> +
>> +static int process_build_id(struct perf_tool *tool,
>> +                           union perf_event *event,
>> +                           struct perf_sample *sample __maybe_unused,
>> +                           struct machine *machine __maybe_unused)
>> +{
>> +       struct perf_inject *inject = container_of(tool, struct perf_inject, tool);
>> +
>> +       return perf_event__process_build_id(inject->session, event);
>> +}
>> +
>> +static int synthesize_build_id(struct perf_inject *inject, struct dso *dso, pid_t machine_pid)
>> +{
>> +       struct machine *machine = perf_session__findnew_machine(inject->session, machine_pid);
>> +       u8 cpumode = dso__is_in_kernel_space(dso) ?
>> +                       PERF_RECORD_MISC_GUEST_KERNEL :
>> +                       PERF_RECORD_MISC_GUEST_USER;
>> +
>> +       if (!machine)
>> +               return -ENOMEM;
>> +
>> +       dso->hit = 1;
>> +
>> +       return perf_event__synthesize_build_id(&inject->tool, dso, cpumode,
>> +                                              process_build_id, machine);
>> +}
>> +
>> +static int guest_session__add_build_ids(struct guest_session *gs)
>> +{
>> +       struct perf_inject *inject = container_of(gs, struct perf_inject, guest_session);
>> +       struct machine *machine = &gs->session->machines.host;
>> +       struct dso *dso;
>> +       int ret;
>> +
>> +       /* Build IDs will be put in the Build ID feature section */
>> +       perf_header__set_feat(&inject->session->header, HEADER_BUILD_ID);
>> +
>> +       dsos__for_each_with_build_id(dso, &machine->dsos.head) {
>> +               ret = synthesize_build_id(inject, dso, gs->machine_pid);
>> +               if (ret)
>> +                       return ret;
>> +       }
>> +
>> +       return 0;
>> +}
>> +
>> +static int guest_session__ksymbol_event(struct perf_tool *tool,
>> +                                       union perf_event *event,
>> +                                       struct perf_sample *sample __maybe_unused,
>> +                                       struct machine *machine __maybe_unused)
>> +{
>> +       struct guest_session *gs = container_of(tool, struct guest_session, tool);
>> +
>> +       /* Only support out-of-line i.e. no BPF support */
>> +       if (event->ksymbol.ksym_type != PERF_RECORD_KSYMBOL_TYPE_OOL)
>> +               return 0;
>> +
>> +       return guest_session__output_bytes(gs, event, event->header.size);
>> +}
>> +
>> +static int guest_session__start(struct guest_session *gs, const char *name, bool force)
>> +{
>> +       char tmp_file_name[] = "/tmp/perf-inject-guest_session-XXXXXX";
>> +       struct perf_session *session;
>> +       int ret;
>> +
>> +       /* Only these events will be injected */
>> +       gs->tool.mmap           = guest_session__repipe;
>> +       gs->tool.mmap2          = guest_session__repipe;
>> +       gs->tool.comm           = guest_session__repipe;
>> +       gs->tool.fork           = guest_session__repipe;
>> +       gs->tool.exit           = guest_session__repipe;
>> +       gs->tool.lost           = guest_session__repipe;
>> +       gs->tool.context_switch = guest_session__repipe;
>> +       gs->tool.ksymbol        = guest_session__ksymbol_event;
>> +       gs->tool.text_poke      = guest_session__repipe;
>> +       /*
>> +        * Processing a build ID creates a struct dso with that build ID. Later,
>> +        * all guest dsos are iterated and the build IDs processed into the host
>> +        * session where they will be output to the Build ID feature section
>> +        * when the perf.data file header is written.
>> +        */
>> +       gs->tool.build_id       = perf_event__process_build_id;
>> +       /* Process the id index to know what VCPU an ID belongs to */
>> +       gs->tool.id_index       = perf_event__process_id_index;
>> +
>> +       gs->tool.ordered_events = true;
>> +       gs->tool.ordering_requires_timestamps = true;
>> +
>> +       gs->data.path   = name;
>> +       gs->data.force  = force;
>> +       gs->data.mode   = PERF_DATA_MODE_READ;
>> +
>> +       session = perf_session__new(&gs->data, &gs->tool);
>> +       if (IS_ERR(session))
>> +               return PTR_ERR(session);
>> +       gs->session = session;
>> +
>> +       /*
>> +        * Initial events have zero'd ID samples. Get default ID sample size
>> +        * used for removing them.
>> +        */
>> +       gs->dflt_id_hdr_size = session->machines.host.id_hdr_size;
>> +       /* And default ID for adding back a host-compatible ID sample */
>> +       gs->dflt_id = evlist__first_id(session->evlist);
>> +       if (!gs->dflt_id) {
>> +               pr_err("Guest data has no sample IDs");
>> +               return -EINVAL;
>> +       }
>> +
>> +       /* Temporary file for guest events */
>> +       gs->tmp_file_name = strdup(tmp_file_name);
>> +       if (!gs->tmp_file_name)
>> +               return -ENOMEM;
>> +       gs->tmp_fd = mkstemp(gs->tmp_file_name);
>> +       if (gs->tmp_fd < 0)
>> +               return -errno;
>> +
>> +       if (zstd_init(&gs->session->zstd_data, 0) < 0)
>> +               pr_warning("Guest session decompression initialization failed.\n");
>> +
>> +       /*
>> +        * perf does not support processing 2 sessions simultaneously, so output
>> +        * guest events to a temporary file.
>> +        */
>> +       ret = perf_session__process_events(gs->session);
>> +       if (ret)
>> +               return ret;
>> +
>> +       if (lseek(gs->tmp_fd, 0, SEEK_SET))
>> +               return -errno;
>> +
>> +       return 0;
>> +}
>> +
>> +/* Free hlist nodes assuming hlist_node is the first member of hlist entries */
>> +static void free_hlist(struct hlist_head *heads, size_t hlist_sz)
>> +{
>> +       struct hlist_node *pos, *n;
>> +       size_t i;
>> +
>> +       for (i = 0; i < hlist_sz; ++i) {
>> +               hlist_for_each_safe(pos, n, &heads[i]) {
>> +                       hlist_del(pos);
>> +                       free(pos);
>> +               }
>> +       }
>> +}
>> +
>> +static void guest_session__exit(struct guest_session *gs)
>> +{
>> +       if (gs->session) {
>> +               perf_session__delete(gs->session);
>> +               free_hlist(gs->heads, PERF_EVLIST__HLIST_SIZE);
>> +               free_hlist(gs->tids, PERF_EVLIST__HLIST_SIZE);
>> +       }
>> +       if (gs->tmp_file_name) {
>> +               if (gs->tmp_fd >= 0)
>> +                       close(gs->tmp_fd);
>> +               unlink(gs->tmp_file_name);
>> +               free(gs->tmp_file_name);
>> +       }
>> +       free(gs->vcpu);
>> +       free(gs->perf_data_file);
>> +}
>> +
>> +static void get_tsc_conv(struct perf_tsc_conversion *tc, struct perf_record_time_conv *time_conv)
>> +{
>> +       tc->time_shift          = time_conv->time_shift;
>> +       tc->time_mult           = time_conv->time_mult;
>> +       tc->time_zero           = time_conv->time_zero;
>> +       tc->time_cycles         = time_conv->time_cycles;
>> +       tc->time_mask           = time_conv->time_mask;
>> +       tc->cap_user_time_zero  = time_conv->cap_user_time_zero;
>> +       tc->cap_user_time_short = time_conv->cap_user_time_short;
>> +}
>> +
>> +static void guest_session__get_tc(struct guest_session *gs)
>> +{
>> +       struct perf_inject *inject = container_of(gs, struct perf_inject, guest_session);
>> +
>> +       get_tsc_conv(&gs->host_tc, &inject->session->time_conv);
>> +       get_tsc_conv(&gs->guest_tc, &gs->session->time_conv);
>> +}
>> +
>> +static void guest_session__convert_time(struct guest_session *gs, u64 guest_time, u64 *host_time)
>> +{
>> +       u64 tsc;
>> +
>> +       if (!guest_time) {
>> +               *host_time = 0;
>> +               return;
>> +       }
>> +
>> +       if (gs->guest_tc.cap_user_time_zero)
>> +               tsc = perf_time_to_tsc(guest_time, &gs->guest_tc);
>> +       else
>> +               tsc = guest_time;
>> +
>> +       /*
>> +        * This is the correct order of operations for x86 if the TSC Offset and
>> +        * Multiplier values are used.
>> +        */
>> +       tsc -= gs->time_offset;
>> +       tsc /= gs->time_scale;
>> +
>> +       if (gs->host_tc.cap_user_time_zero)
>> +               *host_time = tsc_to_perf_time(tsc, &gs->host_tc);
>> +       else
>> +               *host_time = tsc;
>> +}
>> +
>> +static int guest_session__fetch(struct guest_session *gs)
>> +{
>> +       void *buf = gs->ev.event_buf;
>> +       struct perf_event_header *hdr = buf;
>> +       size_t hdr_sz = sizeof(*hdr);
>> +       ssize_t ret;
>> +
>> +       ret = readn(gs->tmp_fd, buf, hdr_sz);
>> +       if (ret < 0)
>> +               return ret;
>> +
>> +       if (!ret) {
>> +               /* Zero size means EOF */
>> +               hdr->size = 0;
>> +               return 0;
>> +       }
>> +
>> +       buf += hdr_sz;
>> +
>> +       ret = readn(gs->tmp_fd, buf, hdr->size - hdr_sz);
>> +       if (ret < 0)
>> +               return ret;
>> +
>> +       gs->ev.event = (union perf_event *)gs->ev.event_buf;
>> +       gs->ev.sample.time = 0;
>> +
>> +       if (hdr->type >= PERF_RECORD_USER_TYPE_START) {
>> +               pr_err("Unexpected type fetching guest event");
>> +               return 0;
>> +       }
>> +
>> +       ret = evlist__parse_sample(gs->session->evlist, gs->ev.event, &gs->ev.sample);
>> +       if (ret) {
>> +               pr_err("Parse failed fetching guest event");
>> +               return ret;
>> +       }
>> +
>> +       if (!gs->have_tc) {
>> +               guest_session__get_tc(gs);
>> +               gs->have_tc = true;
>> +       }
>> +
>> +       guest_session__convert_time(gs, gs->ev.sample.time, &gs->ev.sample.time);
>> +
>> +       return 0;
>> +}
>> +
>> +static int evlist__append_id_sample(struct evlist *evlist, union perf_event *ev,
>> +                                   const struct perf_sample *sample)
>> +{
>> +       struct evsel *evsel;
>> +       void *array;
>> +       int ret;
>> +
>> +       evsel = evlist__id2evsel(evlist, sample->id);
>> +       array = ev;
>> +
>> +       if (!evsel) {
>> +               pr_err("No evsel for id %"PRIu64"\n", sample->id);
>> +               return -EINVAL;
>> +       }
>> +
>> +       array += ev->header.size;
>> +       ret = perf_event__synthesize_id_sample(array, evsel->core.attr.sample_type, sample);
>> +       if (ret < 0)
>> +               return ret;
>> +
>> +       if (ret & 7) {
>> +               pr_err("Bad id sample size %d\n", ret);
>> +               return -EINVAL;
>> +       }
>> +
>> +       ev->header.size += ret;
>> +
>> +       return 0;
>> +}
>> +
>> +static int guest_session__inject_events(struct guest_session *gs, u64 timestamp)
>> +{
>> +       struct perf_inject *inject = container_of(gs, struct perf_inject, guest_session);
>> +       int ret;
>> +
>> +       if (!gs->ready)
>> +               return 0;
>> +
>> +       while (1) {
>> +               struct perf_sample *sample;
>> +               struct guest_id *guest_id;
>> +               union perf_event *ev;
>> +               u16 id_hdr_size;
>> +               u8 cpumode;
>> +               u64 id;
>> +
>> +               if (!gs->fetched) {
>> +                       ret = guest_session__fetch(gs);
>> +                       if (ret)
>> +                               return ret;
>> +                       gs->fetched = true;
>> +               }
>> +
>> +               ev = gs->ev.event;
>> +               sample = &gs->ev.sample;
>> +
>> +               if (!ev->header.size)
>> +                       return 0; /* EOF */
>> +
>> +               if (sample->time > timestamp)
>> +                       return 0;
>> +
>> +               /* Change cpumode to guest */
>> +               cpumode = ev->header.misc & PERF_RECORD_MISC_CPUMODE_MASK;
>> +               if (cpumode & PERF_RECORD_MISC_USER)
>> +                       cpumode = PERF_RECORD_MISC_GUEST_USER;
>> +               else
>> +                       cpumode = PERF_RECORD_MISC_GUEST_KERNEL;
>> +               ev->header.misc &= ~PERF_RECORD_MISC_CPUMODE_MASK;
>> +               ev->header.misc |= cpumode;
>> +
>> +               id = sample->id;
>> +               if (!id) {
>> +                       id = gs->dflt_id;
>> +                       id_hdr_size = gs->dflt_id_hdr_size;
>> +               } else {
>> +                       struct evsel *evsel = evlist__id2evsel(gs->session->evlist, id);
>> +
>> +                       id_hdr_size = evsel__id_hdr_size(evsel);
>> +               }
>> +
>> +               if (id_hdr_size & 7) {
>> +                       pr_err("Bad id_hdr_size %u\n", id_hdr_size);
>> +                       return -EINVAL;
>> +               }
>> +
>> +               if (ev->header.size & 7) {
>> +                       pr_err("Bad event size %u\n", ev->header.size);
>> +                       return -EINVAL;
>> +               }
>> +
>> +               /* Remove guest id sample */
>> +               ev->header.size -= id_hdr_size;
>> +
>> +               if (ev->header.size & 7) {
>> +                       pr_err("Bad raw event size %u\n", ev->header.size);
>> +                       return -EINVAL;
>> +               }
>> +
>> +               guest_id = guest_session__lookup_id(gs, id);
>> +               if (!guest_id) {
>> +                       pr_err("Guest event with unknown id %llu\n",
>> +                              (unsigned long long)id);
>> +                       return -EINVAL;
>> +               }
>> +
>> +               /* Change to host ID to avoid conflicting ID values */
>> +               sample->id = guest_id->host_id;
>> +               sample->stream_id = guest_id->host_id;
>> +
>> +               if (sample->cpu != (u32)-1) {
>> +                       if (sample->cpu >= gs->vcpu_cnt) {
>> +                               pr_err("Guest event with unknown VCPU %u\n",
>> +                                      sample->cpu);
>> +                               return -EINVAL;
>> +                       }
>> +                       /* Change to host CPU instead of guest VCPU */
>> +                       sample->cpu = gs->vcpu[sample->cpu].cpu;
>> +               }
>> +
>> +               /* New id sample with new ID and CPU */
>> +               ret = evlist__append_id_sample(inject->session->evlist, ev, sample);
>> +               if (ret)
>> +                       return ret;
>> +
>> +               if (ev->header.size & 7) {
>> +                       pr_err("Bad new event size %u\n", ev->header.size);
>> +                       return -EINVAL;
>> +               }
>> +
>> +               gs->fetched = false;
>> +
>> +               ret = output_bytes(inject, ev, ev->header.size);
>> +               if (ret)
>> +                       return ret;
>> +       }
>> +}
>> +
>> +static int guest_session__flush_events(struct guest_session *gs)
>> +{
>> +       return guest_session__inject_events(gs, -1);
>> +}
>> +
>> +static int host__repipe(struct perf_tool *tool,
>> +                       union perf_event *event,
>> +                       struct perf_sample *sample,
>> +                       struct machine *machine)
>> +{
>> +       struct perf_inject *inject = container_of(tool, struct perf_inject, tool);
>> +       int ret;
>> +
>> +       ret = guest_session__inject_events(&inject->guest_session, sample->time);
>> +       if (ret)
>> +               return ret;
>> +
>> +       return perf_event__repipe(tool, event, sample, machine);
>> +}
>> +
>> +static int host__finished_init(struct perf_session *session, union perf_event *event)
>> +{
>> +       struct perf_inject *inject = container_of(session->tool, struct perf_inject, tool);
>> +       struct guest_session *gs = &inject->guest_session;
>> +       int ret;
>> +
>> +       /*
>> +        * Peek through host COMM events to find QEMU threads and the VCPU they
>> +        * are running.
>> +        */
>> +       ret = host_peek_vm_comms(session, gs);
>> +       if (ret)
>> +               return ret;
>> +
>> +       if (!gs->vcpu_cnt) {
>> +               pr_err("No VCPU theads found for pid %u\n", gs->machine_pid);
>> +               return -EINVAL;
>> +       }
>> +
>> +       /*
>> +        * Allocate new (unused) host sample IDs and map them to the guest IDs.
>> +        */
>> +       gs->highest_id = evlist__find_highest_id(session->evlist);
>> +       ret = guest_session__map_ids(gs, session->evlist);
>> +       if (ret)
>> +               return ret;
>> +
>> +       ret = guest_session__add_attrs(gs);
>> +       if (ret)
>> +               return ret;
>> +
>> +       ret = synthesize_id_index(inject, gs->session->evlist->core.nr_entries);
>> +       if (ret) {
>> +               pr_err("Failed to synthesize id_index\n");
>> +               return ret;
>> +       }
>> +
>> +       ret = guest_session__add_build_ids(gs);
>> +       if (ret) {
>> +               pr_err("Failed to add guest build IDs\n");
>> +               return ret;
>> +       }
>> +
>> +       gs->ready = true;
>> +
>> +       ret = guest_session__inject_events(gs, 0);
>> +       if (ret)
>> +               return ret;
>> +
>> +       return perf_event__repipe_op2_synth(session, event);
>> +}
>> +
>> +/*
>> + * Obey finished-round ordering. The FINISHED_ROUND event is first processed
>> + * which flushes host events to file up until the last flush time. Then inject
>> + * guest events up to the same time. Finally write out the FINISHED_ROUND event
>> + * itself.
>> + */
>> +static int host__finished_round(struct perf_tool *tool,
>> +                               union perf_event *event,
>> +                               struct ordered_events *oe)
>> +{
>> +       struct perf_inject *inject = container_of(tool, struct perf_inject, tool);
>> +       int ret = perf_event__process_finished_round(tool, event, oe);
>> +       u64 timestamp = ordered_events__last_flush_time(oe);
>> +
>> +       if (ret)
>> +               return ret;
>> +
>> +       ret = guest_session__inject_events(&inject->guest_session, timestamp);
>> +       if (ret)
>> +               return ret;
>> +
>> +       return perf_event__repipe_oe_synth(tool, event, oe);
>> +}
>> +
>> +static int host__context_switch(struct perf_tool *tool,
>> +                               union perf_event *event,
>> +                               struct perf_sample *sample,
>> +                               struct machine *machine)
>> +{
>> +       struct perf_inject *inject = container_of(tool, struct perf_inject, tool);
>> +       bool out = event->header.misc & PERF_RECORD_MISC_SWITCH_OUT;
>> +       struct guest_session *gs = &inject->guest_session;
>> +       u32 pid = event->context_switch.next_prev_pid;
>> +       u32 tid = event->context_switch.next_prev_tid;
>> +       struct guest_tid *guest_tid;
>> +       u32 vcpu;
>> +
>> +       if (out || pid != gs->machine_pid)
>> +               goto out;
>> +
>> +       guest_tid = guest_session__lookup_tid(gs, tid);
>> +       if (!guest_tid)
>> +               goto out;
>> +
>> +       if (sample->cpu == (u32)-1) {
>> +               pr_err("Switch event does not have CPU\n");
>> +               return -EINVAL;
>> +       }
>> +
>> +       vcpu = guest_tid->vcpu;
>> +       if (vcpu >= gs->vcpu_cnt)
>> +               return -EINVAL;
>> +
>> +       /* Guest is switching in, record which CPU the VCPU is now running on */
>> +       gs->vcpu[vcpu].cpu = sample->cpu;
>> +out:
>> +       return host__repipe(tool, event, sample, machine);
>> +}
>> +
>>  static void sig_handler(int sig __maybe_unused)
>>  {
>>         session_done = 1;
>> @@ -767,6 +1666,61 @@ static int parse_vm_time_correlation(const struct option *opt, const char *str,
>>         return inject->itrace_synth_opts.vm_tm_corr_args ? 0 : -ENOMEM;
>>  }
>>
>> +static int parse_guest_data(const struct option *opt, const char *str, int unset)
>> +{
>> +       struct perf_inject *inject = opt->value;
>> +       struct guest_session *gs = &inject->guest_session;
>> +       char *tok;
>> +       char *s;
>> +
>> +       if (unset)
>> +               return 0;
>> +
>> +       if (!str)
>> +               goto bad_args;
>> +
>> +       s = strdup(str);
>> +       if (!s)
>> +               return -ENOMEM;
>> +
>> +       gs->perf_data_file = strsep(&s, ",");
>> +       if (!gs->perf_data_file)
>> +               goto bad_args;
>> +
>> +       gs->copy_kcore_dir = has_kcore_dir(gs->perf_data_file);
>> +       if (gs->copy_kcore_dir)
>> +               inject->output.is_dir = true;
>> +
>> +       tok = strsep(&s, ",");
>> +       if (!tok)
>> +               goto bad_args;
>> +       gs->machine_pid = strtoul(tok, NULL, 0);
>> +       if (!inject->guest_session.machine_pid)
>> +               goto bad_args;
>> +
>> +       gs->time_scale = 1;
>> +
>> +       tok = strsep(&s, ",");
>> +       if (!tok)
>> +               goto out;
>> +       gs->time_offset = strtoull(tok, NULL, 0);
>> +
>> +       tok = strsep(&s, ",");
>> +       if (!tok)
>> +               goto out;
>> +       gs->time_scale = strtod(tok, NULL);
>> +       if (!gs->time_scale)
>> +               goto bad_args;
>> +out:
>> +       return 0;
>> +
>> +bad_args:
>> +       pr_err("--guest-data option requires guest perf.data file name, "
>> +              "guest machine PID, and optionally guest timestamp offset, "
>> +              "and guest timestamp scale factor, separated by commas.\n");
>> +       return -1;
>> +}
>> +
>>  static int save_section_info_cb(struct perf_file_section *section,
>>                                 struct perf_header *ph __maybe_unused,
>>                                 int feat, int fd __maybe_unused, void *data)
>> @@ -896,6 +1850,22 @@ static int copy_kcore_dir(struct perf_inject *inject)
>>         return ret;
>>  }
>>
>> +static int guest_session__copy_kcore_dir(struct guest_session *gs)
>> +{
>> +       struct perf_inject *inject = container_of(gs, struct perf_inject, guest_session);
>> +       char *cmd;
>> +       int ret;
>> +
>> +       ret = asprintf(&cmd, "cp -r -n %s/kcore_dir %s/kcore_dir__%u >/dev/null 2>&1",
>> +                      gs->perf_data_file, inject->output.path, gs->machine_pid);
>> +       if (ret < 0)
>> +               return ret;
>> +       pr_debug("%s\n", cmd);
>> +       ret = system(cmd);
>> +       free(cmd);
>> +       return ret;
>> +}
>> +
>>  static int output_fd(struct perf_inject *inject)
>>  {
>>         return inject->in_place_update ? -1 : perf_data__fd(&inject->output);
>> @@ -904,6 +1874,7 @@ static int output_fd(struct perf_inject *inject)
>>  static int __cmd_inject(struct perf_inject *inject)
>>  {
>>         int ret = -EINVAL;
>> +       struct guest_session *gs = &inject->guest_session;
>>         struct perf_session *session = inject->session;
>>         int fd = output_fd(inject);
>>         u64 output_data_offset;
>> @@ -968,6 +1939,47 @@ static int __cmd_inject(struct perf_inject *inject)
>>                 output_data_offset = roundup(8192 + session->header.data_offset, 4096);
>>                 if (inject->strip)
>>                         strip_init(inject);
>> +       } else if (gs->perf_data_file) {
>> +               char *name = gs->perf_data_file;
>> +
>> +               /*
>> +                * Not strictly necessary, but keep these events in order wrt
>> +                * guest events.
>> +                */
>> +               inject->tool.mmap               = host__repipe;
>> +               inject->tool.mmap2              = host__repipe;
>> +               inject->tool.comm               = host__repipe;
>> +               inject->tool.fork               = host__repipe;
>> +               inject->tool.exit               = host__repipe;
>> +               inject->tool.lost               = host__repipe;
>> +               inject->tool.context_switch     = host__repipe;
>> +               inject->tool.ksymbol            = host__repipe;
>> +               inject->tool.text_poke          = host__repipe;
>> +               /*
>> +                * Once the host session has initialized, set up sample ID
>> +                * mapping and feed in guest attrs, build IDs and initial
>> +                * events.
>> +                */
>> +               inject->tool.finished_init      = host__finished_init;
>> +               /* Obey finished round ordering */
>> +               inject->tool.finished_round     = host__finished_round,
>> +               /* Keep track of which CPU a VCPU is runnng on */
>> +               inject->tool.context_switch     = host__context_switch;
>> +               /*
>> +                * Must order events to be able to obey finished round
>> +                * ordering.
>> +                */
>> +               inject->tool.ordered_events     = true;
>> +               inject->tool.ordering_requires_timestamps = true;
>> +               /* Set up a separate session to process guest perf.data file */
>> +               ret = guest_session__start(gs, name, session->data->force);
>> +               if (ret) {
>> +                       pr_err("Failed to process %s, error %d\n", name, ret);
>> +                       return ret;
>> +               }
>> +               /* Allow space in the header for guest attributes */
>> +               output_data_offset += gs->session->header.data_offset;
>> +               output_data_offset = roundup(output_data_offset, 4096);
>>         }
>>
>>         if (!inject->itrace_synth_opts.set)
>> @@ -980,6 +1992,18 @@ static int __cmd_inject(struct perf_inject *inject)
>>         if (ret)
>>                 return ret;
>>
>> +       if (gs->session) {
>> +               /*
>> +                * Remaining guest events have later timestamps. Flush them
>> +                * out to file.
>> +                */
>> +               ret = guest_session__flush_events(gs);
>> +               if (ret) {
>> +                       pr_err("Failed to flush guest events\n");
>> +                       return ret;
>> +               }
>> +       }
>> +
>>         if (!inject->is_pipe && !inject->in_place_update) {
>>                 struct inject_fc inj_fc = {
>>                         .fc.copy = feat_copy_cb,
>> @@ -1014,8 +2038,17 @@ static int __cmd_inject(struct perf_inject *inject)
>>
>>                 if (inject->copy_kcore_dir) {
>>                         ret = copy_kcore_dir(inject);
>> -                       if (ret)
>> +                       if (ret) {
>> +                               pr_err("Failed to copy kcore\n");
>>                                 return ret;
>> +                       }
>> +               }
>> +               if (gs->copy_kcore_dir) {
>> +                       ret = guest_session__copy_kcore_dir(gs);
>> +                       if (ret) {
>> +                               pr_err("Failed to copy guest kcore\n");
>> +                               return ret;
>> +                       }
>>                 }
>>         }
>>
>> @@ -1113,6 +2146,12 @@ int cmd_inject(int argc, const char **argv)
>>                 OPT_CALLBACK_OPTARG(0, "vm-time-correlation", &inject, NULL, "opts",
>>                                     "correlate time between VM guests and the host",
>>                                     parse_vm_time_correlation),
>> +               OPT_CALLBACK_OPTARG(0, "guest-data", &inject, NULL, "opts",
>> +                                   "inject events from a guest perf.data file",
>> +                                   parse_guest_data),
>> +               OPT_STRING(0, "guestmount", &symbol_conf.guestmount, "directory",
>> +                          "guest mount directory under which every guest os"
>> +                          " instance has a subdir"),
> 
> Should guestmount also be in the man page? Also should it have a
> hyphen like guest-data?

Sent a patch to update the man page.

It is "guestmount" in other tools so we should stick with that.

> 
> Thanks,
> Ian
> 
>>                 OPT_END()
>>         };
>>         const char * const inject_usage[] = {
>> @@ -1243,6 +2282,8 @@ int cmd_inject(int argc, const char **argv)
>>
>>         ret = __cmd_inject(&inject);
>>
>> +       guest_session__exit(&inject.guest_session);
>> +
>>  out_delete:
>>         zstd_fini(&(inject.session->zstd_data));
>>         perf_session__delete(inject.session);
>> --
>> 2.25.1
>>