From: Suzuki K Poulose suzuki.poulose@arm.com
The pid of the task could be traced as VMID when the kernel is running at EL2. Teach the decoder to look for vmid when the context_id is invalid but we have a valid VMID.
Cc: Mike Leach mike.leach@linaro.org Cc: Leo Yan leo.yan@linaro.org Cc: Mathieu Poirier mathieu.poirier@linaro.org Signed-off-by: Suzuki K Poulose suzuki.poulose@arm.com
Ideally, we should also confirm that the VMID_OPT is also set in the trcconfigr for choosing the VMID. Hence the RFC. May be that is something we could cache in the "decoder" instance ?
.../perf/util/cs-etm-decoder/cs-etm-decoder.c | 28 +++++++++++-------- 1 file changed, 17 insertions(+), 11 deletions(-)
diff --git a/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c b/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c index cd007cc9c283..31ba7ff57914 100644 --- a/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c +++ b/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c @@ -502,19 +502,25 @@ cs_etm_decoder__set_tid(struct cs_etm_queue *etmq, { pid_t tid;
- /* Ignore PE_CONTEXT packets that don't have a valid contextID */
- if (!elem->context.ctxt_id_valid)
return OCSD_RESP_CONT;- tid = elem->context.context_id;
- if (cs_etm__etmq_set_tid(etmq, tid, trace_chan_id))
return OCSD_RESP_FATAL_SYS_ERR;- /*
* A timestamp is generated after a PE_CONTEXT element so make sure* to rely on that coming one.
* Process the PE_CONTEXT packets if we have a valid* contextID or VMID.* If the kernel is running at EL2, the PID is traced* in contextidr_el2 as VMID.
- cs_etm_decoder__reset_timestamp(packet_queue);
- if (elem->context.ctxt_id_valid || elem->context.vmid_valid) {
if (elem->context.ctxt_id_valid)tid = elem->context.context_id;elsetid = elem->context.vmid;if (cs_etm__etmq_set_tid(etmq, tid, trace_chan_id))return OCSD_RESP_FATAL_SYS_ERR;/** A timestamp is generated after a PE_CONTEXT element somake sure
* to rely on that coming one.*/cs_etm_decoder__reset_timestamp(packet_queue);}
return OCSD_RESP_CONT;
}
So if both CONTEXTID and VMID fields are valid, it will take the TID from CONTEXTID? That seems to make the assumption that...
- it is valid to have VMID in trace from an EL1 kernel (and it should be ignored in favour of getting TID from CONTEXID)
- for an EL2 kernel, where we need to get TID from VMID, we are guaranteed to not have valid CONTEXTID
This seems the wrong way round. An EL2 kernel might want to trace its EL1 guests' CONTEXTID to disambiguate guest processes - right now I don't believe we could make use of this in perf, but it's information that is meaningful in an EL2 kernel's trace. On the other hand, an EL1 kernel's trace doesn't have any business with VMID (which would be the actual VM id) - if an EL1 kernel was capturing trace from other VMs in a trace buffer, that's a big security hole.
It's safer if perf.data has an explicit indication of which field the TID is in - that indicator should be either somewhere in AUXTRACE_INFO or in one of the config fields in the attribute, or a bit in the PERF_RECORD_AUX record. But if you must do it heuristically at decode time based on what you see in packets, then it would be safer to say that if you see both VMID and CONTEXIDR, the TID will be in VMID.
Al
-- 2.24.1