This patch series is to support PID tracing with Virtualization Host Extensions (VHE).
Since the patch series v1 was sent out for reviewing, we had some discussion and finalized the solution which is implemented in this version. Simply to say, to be backward compatibility, and can both support PID tracing for the kernel is running at either EL1 or EL2, the two new PMU formats "contextid1" and "contextid2" are introduced, which works as a switch to trace PID for EL1 kernel and EL2 kernel respectively.
The existed PMU format "contextid" needs to be backward compatible for users, it's changed to an alias for "contextid1" on EL1 kernel and for "contextid2" on EL2 kernel. Therefore, even without setting "contextid" config, the perf tool can dynamically pick up the config for PID tracing, so the user doesn't have to set the "contexid" config manually.
As results, we now have three PMU formats, for easier understanding the implementation, just copy and paste the descriptions for these three PMU formats from the patch 07/07:
"contextid1": Available on both EL1 kernel and EL2 kernel. When the kernel is running at EL1, "contextid1" enables the PID tracing; when the kernel is running at EL2, this enables tracing the PID of guest applications.
"contextid2": Only usable when the kernel is running at EL2. When selected, enables PID tracing on EL2 kernel.
"contextid": Will be an alias for the option that enables PID tracing. I.e, contextid == contextid1, on EL1 kernel. contextid == contextid2, on EL2 kernel.
This patch series can be cleanly applied on perf/core branch:
commit cd07e536b020 ("Merge remote-tracking branch 'torvalds/master' into perf/core")
... and applied on the mainline kernel:
commit 88bb507a74ea ("Merge tag 'media/v5.11-3' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media")
The patch series has been tested on Arm Juno-r2 board. Verified the kernel with EL1 and didn't find issue; though absenting the platform for kernel with EL2, after some hacking in kernel driver and tool to emulate the code paths for kernel on EL2, can see the code path is hit without failure.
Changes from v1: * Refactored PMU formats, added formats "contextid1"/"contextid2", and reworked format "contextid" (Suzuki/Mathieu); * Refined the comments for perf configs (Leo/Mike); * Added patch 07/07 for description PID tracing in docs; * Found the issue for bitmap for option, extracted patch 03/07 for the fixing.
Changes from RFC: * Added comments to clarify cases requested (Leo); * Explain the change to generic flags for cs_etm_set_option() in the commit description; * Stored PID format in metadata and passed it to decoder (Leo); * Enhanced cs-etm for backward compatibility (Denis Nikitin).
Leo Yan (3): coresight: etm-perf: Clarify comment on perf options perf cs-etm: Add helper cs_etm__get_pid_fmt() Documentation: coresight: Add PID tracing description
Suzuki K Poulose (4): coresight: etm-perf: Support PID tracing for kernel at EL2 perf cs-etm: Fix bitmap for option perf cs-etm: Support PID tracing in config perf cs-etm: Detect pid in VMID for kernel running at EL2
Documentation/trace/coresight/coresight.rst | 37 ++++++++++ .../hwtracing/coresight/coresight-etm-perf.c | 32 +++++++- .../coresight/coresight-etm4x-core.c | 13 ++++ include/linux/coresight-pmu.h | 20 +++-- tools/include/linux/coresight-pmu.h | 20 +++-- tools/perf/arch/arm/util/cs-etm.c | 73 +++++++++++++++---- .../perf/util/cs-etm-decoder/cs-etm-decoder.c | 32 +++++++- tools/perf/util/cs-etm.c | 43 +++++++++++ tools/perf/util/cs-etm.h | 1 + 9 files changed, 239 insertions(+), 32 deletions(-)