| Message ID | 20210109074435.626855-1-leo.yan@linaro.org (mailing list archive) |
|---|---|
| Headers | show |
| Series | coresight: etm-perf: Fix pid tracing with VHE | expand |
Hi Leo, Suzuki and Mike have pointed out a few things to modify and there was a couple of kernel bot warnings to address as well. As such I will wait for your next revision before looking at this set. Thanks, Mathieu On Sat, Jan 09, 2021 at 03:44:28PM +0800, Leo Yan wrote: > This patch series is a following up for the previous version which was > delivered by Suzuki [1]. Below gives the background info for why we > need this patch series, directly quotes the description in the cover > letter of the previous version: > > "With the Virtualization Host Extensions, the kernel can run at EL2. > In this case the pid is written to CONTEXTIDR_EL2 instead of the > CONTEXTIDR_EL1. Thus the normal coresight tracing will be unable > to detect the PID of the thread generating the trace by looking > at the CONTEXTIDR_EL1. Thus, depending on the kernel EL, we must > switch to tracing the correct CONTEXTIDR register. > > With VHE, we must set the TRCCONFIGR.VMID and TRCCONFIGR.VMID_OPT > to include the CONTEXTIDR_EL2 as the VMID in the trace. This > requires the perf tool to detect the changes in the TRCCONFIGR and > use the VMID / CID field for the PID. The challenge here is for > the perf tool to detect the kernel behavior. > > Instead of the previously proposed invasive approaches, this set > implements a less intrusive mechanism, by playing with the > perf_event.attribute.config bits." > > Same as the previous series, this series keeps the same implementation > for two introduced format bits: > > - contextid_in_vmid -> Is only supported when the VMID tracing > and CONTEXTIDR_EL2 both are supported. When requested the perf > etm4x backend sets (TRCCONFIGR.VMID | TRCCONFIGR.VMID_OPT). > As per ETMv4.4 TRM, when the core supports VHE, the CONTEXTIDR_EL2 > tracing is mandatory. (See the field TRCID2.VMIDOPT) > > - pid -> Is an alias for the correct config to enable PID tracing > on any kernel. > i.e, in EL1 kernel -> pid == contextid > EL2 kernel -> pid == contextid_in_vmid > > With this, the perf tool is also updated to request the "pid" > tracing whenever available, falling back to "contextid" if it > is unavailable. > > Comparing against the old version, this patch series uses the metadata > to save PID format; after add new item into metadata, it introduces > backward compatibility issue. To allow backward compatibility, this > series calculates per CPU metadata array size and avoid to use the > defined macro, so can always know the correct array size based on the > info stored in perf data file. Finally, the PID format stored in > metadata is passed to decoder and guide the decoder to set PID from > CONTEXTIDR_EL1 or VMID. > > This patch series has been tested on Arm Juno-r2 board, with testing > two perf data files: one data file is recorded by the latest perf tool > after applied this patch series, and another data file is recorded by > old perf tool without this patch series, so this can prove the tool is > backward compatible. > > 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). > > [1] https://archive.armlinux.org.uk/lurker/message/20201110.183310.24406f33.en.html > > > Leo Yan (4): > perf cs-etm: Calculate per CPU metadata array size > perf cs-etm: Add PID format into metadata > perf cs-etm: Fixup PID_FMT when it is zero > perf cs-etm: Add helper cs_etm__get_pid_fmt() > > Suzuki K Poulose (3): > coresight: etm-perf: Add support for PID tracing for kernel at EL2 > perf cs_etm: Use pid tracing explicitly instead of contextid > perf cs-etm: Detect pid in VMID for kernel running at EL2 > > .../hwtracing/coresight/coresight-etm-perf.c | 14 +++ > .../coresight/coresight-etm4x-core.c | 9 ++ > include/linux/coresight-pmu.h | 11 ++- > tools/include/linux/coresight-pmu.h | 11 ++- > tools/perf/arch/arm/util/cs-etm.c | 89 +++++++++++++++---- > .../perf/util/cs-etm-decoder/cs-etm-decoder.c | 32 ++++++- > tools/perf/util/cs-etm.c | 61 ++++++++++++- > tools/perf/util/cs-etm.h | 3 + > 8 files changed, 198 insertions(+), 32 deletions(-) > > -- > 2.25.1 >
On Mon, Jan 11, 2021 at 11:16:46AM -0700, Mathieu Poirier wrote: > Hi Leo, > > Suzuki and Mike have pointed out a few things to modify and there was a couple > of kernel bot warnings to address as well. As such I will wait for your next > revision before looking at this set. Yeah, this is fine for me. > Thanks, > Mathieu > > On Sat, Jan 09, 2021 at 03:44:28PM +0800, Leo Yan wrote: > > This patch series is a following up for the previous version which was > > delivered by Suzuki [1]. Below gives the background info for why we > > need this patch series, directly quotes the description in the cover > > letter of the previous version: > > > > "With the Virtualization Host Extensions, the kernel can run at EL2. > > In this case the pid is written to CONTEXTIDR_EL2 instead of the > > CONTEXTIDR_EL1. Thus the normal coresight tracing will be unable > > to detect the PID of the thread generating the trace by looking > > at the CONTEXTIDR_EL1. Thus, depending on the kernel EL, we must > > switch to tracing the correct CONTEXTIDR register. > > > > With VHE, we must set the TRCCONFIGR.VMID and TRCCONFIGR.VMID_OPT > > to include the CONTEXTIDR_EL2 as the VMID in the trace. This > > requires the perf tool to detect the changes in the TRCCONFIGR and > > use the VMID / CID field for the PID. The challenge here is for > > the perf tool to detect the kernel behavior. > > > > Instead of the previously proposed invasive approaches, this set > > implements a less intrusive mechanism, by playing with the > > perf_event.attribute.config bits." > > > > Same as the previous series, this series keeps the same implementation > > for two introduced format bits: > > > > - contextid_in_vmid -> Is only supported when the VMID tracing > > and CONTEXTIDR_EL2 both are supported. When requested the perf > > etm4x backend sets (TRCCONFIGR.VMID | TRCCONFIGR.VMID_OPT). > > As per ETMv4.4 TRM, when the core supports VHE, the CONTEXTIDR_EL2 > > tracing is mandatory. (See the field TRCID2.VMIDOPT) > > > > - pid -> Is an alias for the correct config to enable PID tracing > > on any kernel. > > i.e, in EL1 kernel -> pid == contextid > > EL2 kernel -> pid == contextid_in_vmid > > > > With this, the perf tool is also updated to request the "pid" > > tracing whenever available, falling back to "contextid" if it > > is unavailable. > > > > Comparing against the old version, this patch series uses the metadata > > to save PID format; after add new item into metadata, it introduces > > backward compatibility issue. To allow backward compatibility, this > > series calculates per CPU metadata array size and avoid to use the > > defined macro, so can always know the correct array size based on the > > info stored in perf data file. Finally, the PID format stored in > > metadata is passed to decoder and guide the decoder to set PID from > > CONTEXTIDR_EL1 or VMID. > > > > This patch series has been tested on Arm Juno-r2 board, with testing > > two perf data files: one data file is recorded by the latest perf tool > > after applied this patch series, and another data file is recorded by > > old perf tool without this patch series, so this can prove the tool is > > backward compatible. > > > > 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). > > > > [1] https://archive.armlinux.org.uk/lurker/message/20201110.183310.24406f33.en.html > > > > > > Leo Yan (4): > > perf cs-etm: Calculate per CPU metadata array size > > perf cs-etm: Add PID format into metadata > > perf cs-etm: Fixup PID_FMT when it is zero > > perf cs-etm: Add helper cs_etm__get_pid_fmt() > > > > Suzuki K Poulose (3): > > coresight: etm-perf: Add support for PID tracing for kernel at EL2 > > perf cs_etm: Use pid tracing explicitly instead of contextid > > perf cs-etm: Detect pid in VMID for kernel running at EL2 > > > > .../hwtracing/coresight/coresight-etm-perf.c | 14 +++ > > .../coresight/coresight-etm4x-core.c | 9 ++ > > include/linux/coresight-pmu.h | 11 ++- > > tools/include/linux/coresight-pmu.h | 11 ++- > > tools/perf/arch/arm/util/cs-etm.c | 89 +++++++++++++++---- > > .../perf/util/cs-etm-decoder/cs-etm-decoder.c | 32 ++++++- > > tools/perf/util/cs-etm.c | 61 ++++++++++++- > > tools/perf/util/cs-etm.h | 3 + > > 8 files changed, 198 insertions(+), 32 deletions(-) > > > > -- > > 2.25.1 > >
This patch series is a following up for the previous version which was delivered by Suzuki [1]. Below gives the background info for why we need this patch series, directly quotes the description in the cover letter of the previous version: "With the Virtualization Host Extensions, the kernel can run at EL2. In this case the pid is written to CONTEXTIDR_EL2 instead of the CONTEXTIDR_EL1. Thus the normal coresight tracing will be unable to detect the PID of the thread generating the trace by looking at the CONTEXTIDR_EL1. Thus, depending on the kernel EL, we must switch to tracing the correct CONTEXTIDR register. With VHE, we must set the TRCCONFIGR.VMID and TRCCONFIGR.VMID_OPT to include the CONTEXTIDR_EL2 as the VMID in the trace. This requires the perf tool to detect the changes in the TRCCONFIGR and use the VMID / CID field for the PID. The challenge here is for the perf tool to detect the kernel behavior. Instead of the previously proposed invasive approaches, this set implements a less intrusive mechanism, by playing with the perf_event.attribute.config bits." Same as the previous series, this series keeps the same implementation for two introduced format bits: - contextid_in_vmid -> Is only supported when the VMID tracing and CONTEXTIDR_EL2 both are supported. When requested the perf etm4x backend sets (TRCCONFIGR.VMID | TRCCONFIGR.VMID_OPT). As per ETMv4.4 TRM, when the core supports VHE, the CONTEXTIDR_EL2 tracing is mandatory. (See the field TRCID2.VMIDOPT) - pid -> Is an alias for the correct config to enable PID tracing on any kernel. i.e, in EL1 kernel -> pid == contextid EL2 kernel -> pid == contextid_in_vmid With this, the perf tool is also updated to request the "pid" tracing whenever available, falling back to "contextid" if it is unavailable. Comparing against the old version, this patch series uses the metadata to save PID format; after add new item into metadata, it introduces backward compatibility issue. To allow backward compatibility, this series calculates per CPU metadata array size and avoid to use the defined macro, so can always know the correct array size based on the info stored in perf data file. Finally, the PID format stored in metadata is passed to decoder and guide the decoder to set PID from CONTEXTIDR_EL1 or VMID. This patch series has been tested on Arm Juno-r2 board, with testing two perf data files: one data file is recorded by the latest perf tool after applied this patch series, and another data file is recorded by old perf tool without this patch series, so this can prove the tool is backward compatible. 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). [1] https://archive.armlinux.org.uk/lurker/message/20201110.183310.24406f33.en.html Leo Yan (4): perf cs-etm: Calculate per CPU metadata array size perf cs-etm: Add PID format into metadata perf cs-etm: Fixup PID_FMT when it is zero perf cs-etm: Add helper cs_etm__get_pid_fmt() Suzuki K Poulose (3): coresight: etm-perf: Add support for PID tracing for kernel at EL2 perf cs_etm: Use pid tracing explicitly instead of contextid perf cs-etm: Detect pid in VMID for kernel running at EL2 .../hwtracing/coresight/coresight-etm-perf.c | 14 +++ .../coresight/coresight-etm4x-core.c | 9 ++ include/linux/coresight-pmu.h | 11 ++- tools/include/linux/coresight-pmu.h | 11 ++- tools/perf/arch/arm/util/cs-etm.c | 89 +++++++++++++++---- .../perf/util/cs-etm-decoder/cs-etm-decoder.c | 32 ++++++- tools/perf/util/cs-etm.c | 61 ++++++++++++- tools/perf/util/cs-etm.h | 3 + 8 files changed, 198 insertions(+), 32 deletions(-)