CoreSight

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Re: [PATCH 4/5] perf arm-spe: Implement find_snapshot callback

by James Clark

On 12/10/2021 09:19, Will Deacon wrote: > On Mon, Oct 11, 2021 at 04:55:37PM +0100, German Gomez wrote: >> Hi Leo, >> >> On 06/10/2021 10:51, Leo Yan wrote: >>> On Wed, Oct 06, 2021 at 10:35:20AM +0100, German Gomez wrote: >>> >>> [...] >>> >>>>> So simply say, I think the head pointer monotonically increasing is >>>>> the right thing to do in Arm SPE driver. >>>> I will talk to James about how we can proceed on this. >>> Thanks! >> >> I took this offline with James and, though it looks possible to patch >> the SPE driver to have a monotonically increasing head pointer in order >> to simplify the handling in the perf tool, it could be a breaking change >> for users of the perf_event_open syscall that currently rely on the way >> it works now. >> >> An alternative way we considered to simplify the patch is to change the >> logic inside the find_snapshot callback so that it records the entire >> contents of the aux buffer every time. >> >> What do you think? > > What does intel-pt do? Intel-pt has a wrapped head, which is why it has the intel_pt_find_snapshot() function in perf to try to not save any zeros from the buffer that haven't been written yet. (With a wrapped head pointer it's impossible to tell). Coresight has a monotonically increasing head pointer so it is possible to tell. Recently, Leo removed the Coresight version of find_snapshot() for this reason. It would be nice to do the same for SPE because that function has a heuristic and is also slow, but I imagine that not returning wrapped head pointers could break anything that expects them. James > > Will >

5 years, 1 month

Re: [PATCH v3 15/16] arm64: errata: Advertise the workaround for TSB flush failures

by Suzuki K Poulose

On 11/10/2021 11:18, Will Deacon wrote: > On Fri, Oct 08, 2021 at 07:29:05PM +0100, Suzuki K Poulose wrote: >> Advertise the workaround for the TSB flush failures via >> Kconfig entries. >> >> Cc: Will Deacon <will(a)kernel.org> >> Cc: Catalin Marinas <catalin.marinas(a)arm.com> >> Cc: Mathieu Poirier <mathieu.poirier(a)linaro.org> >> Cc: Anshuman Khandual <anshuman.khandual(a)arm.com> >> Cc: Marc Zyngier <maz(a)kernel.org> >> Reviewed-by: Mathieu Poirier <mathieu.poirier(a)linaro.org> >> Acked-by: Catalin Marinas <catalin.marinas(a)arm.com> >> Signed-off-by: Suzuki K Poulose <suzuki.poulose(a)arm.com> >> --- >> Changes since previous: >> - Split the Kconfig/erratum updates to keep the conflicts >> minimal with the other Kconfig updates in TRBE errata >> I have retained the tags >> --- >> Documentation/arm64/silicon-errata.rst | 4 ++++ >> arch/arm64/Kconfig | 31 ++++++++++++++++++++++++++ >> 2 files changed, 35 insertions(+) >> >> diff --git a/Documentation/arm64/silicon-errata.rst b/Documentation/arm64/silicon-errata.rst >> index 2f99229d993c..569a92411dcd 100644 >> --- a/Documentation/arm64/silicon-errata.rst >> +++ b/Documentation/arm64/silicon-errata.rst >> @@ -94,6 +94,8 @@ stable kernels. >> +----------------+-----------------+-----------------+-----------------------------+ >> | ARM | Cortex-A710 | #2119858 | ARM64_ERRATUM_2119858 | >> +----------------+-----------------+-----------------+-----------------------------+ >> +| ARM | Cortex-A710 | #2054223 | ARM64_ERRATUM_2054223 | >> ++----------------+-----------------+-----------------+-----------------------------+ >> | ARM | Neoverse-N1 | #1188873,1418040| ARM64_ERRATUM_1418040 | >> +----------------+-----------------+-----------------+-----------------------------+ >> | ARM | Neoverse-N1 | #1349291 | N/A | >> @@ -102,6 +104,8 @@ stable kernels. >> +----------------+-----------------+-----------------+-----------------------------+ >> | ARM | Neoverse-N2 | #2139208 | ARM64_ERRATUM_2139208 | >> +----------------+-----------------+-----------------+-----------------------------+ >> +| ARM | Neoverse-N2 | #2067961 | ARM64_ERRATUM_2067961 | >> ++----------------+-----------------+-----------------+-----------------------------+ >> | ARM | MMU-500 | #841119,826419 | N/A | >> +----------------+-----------------+-----------------+-----------------------------+ >> +----------------+-----------------+-----------------+-----------------------------+ >> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig >> index eac4030322df..0764774e12bb 100644 >> --- a/arch/arm64/Kconfig >> +++ b/arch/arm64/Kconfig >> @@ -705,6 +705,37 @@ config ARM64_ERRATUM_2139208 >> >> If unsure, say Y. >> >> +config ARM64_WORKAROUND_TSB_FLUSH_FAILURE >> + bool >> + >> +config ARM64_ERRATUM_2054223 >> + bool "Cortex-A710: 2054223: workaround TSB instruction failing to flush trace" >> + default y >> + help >> + Enable workaround for ARM Cortex-A710 erratum 2054223 >> + >> + Affected cores may fail to flush the trace data on a TSB instruction, when >> + the PE is in trace prohibited state. This will cause losing a few bytes >> + of the trace cached. >> + >> + Workaround is to issue two TSB consecutively on affected cores. >> + >> + If unsure, say Y. >> + >> +config ARM64_ERRATUM_2067961 >> + bool "Neoverse-N2: 2067961: workaround TSB instruction failing to flush trace" >> + default y >> + help >> + Enable workaround for ARM Neoverse-N2 erratum 2067961 >> + >> + Affected cores may fail to flush the trace data on a TSB instruction, when >> + the PE is in trace prohibited state. This will cause losing a few bytes >> + of the trace cached. >> + >> + Workaround is to issue two TSB consecutively on affected cores. >> + >> + If unsure, say Y. > > Shouldn't these two be selecting the workaround? doh! I have given myself a slap for this and fixed it locally. Suzuki

5 years, 1 month

[PATCH v3 00/16] arm64: Self-hosted trace related errata workarounds

by Suzuki K Poulose

This series adds CPU erratum work arounds related to the self-hosted tracing. The list of affected errata handled in this series are : * TRBE may overwrite trace in FILL mode - Arm Neoverse-N2 #2139208 - Cortex-A710 #211985 * A TSB instruction may not flush the trace completely when executed in trace prohibited region. - Arm Neoverse-N2 #2067961 - Cortex-A710 #2054223 * TRBE may write to out-of-range address - Arm Neoverse-N2 #2253138 - Cortex-A710 #2224489 The series applies on coresight/next. The series has been reordered to make it easier to merge the patches via arm64 tree and the coresight tree. Patches 1-4 are could be picked up via arm64 tree. The rest can go via the coresight tree. All Kconfig changes are at the end of the series and could go via the coresight tree to make sure that the work arounds are available in the final tree before they can be selected by the user. A tree is available here : git@git.gitlab.arm.com:linux-arm/linux-skp.git coresight/errata/trbe-tsb-n2-a710/v3 Changes since v2: * https://lkml.kernel.org/r/20210921134121.2423546-1-suzuki.poulose@arm.com - Dropped patch adding a helper to reach cpudata from perf handle - Split the TSB erratum work around patch to split the Kconfig/erratum list update changes(pushed to the end of the series). - Added wrappers to check the erratum : trbe_has_erratum(cpudata, TRBE_ERRATUM_<TITLE>) -> trbe_may_<title> - More ASCII art explanation on workaround. Changes since v1: * https://lkml.kernel.org/r/20210728135217.591173-1-suzuki.poulose@arm.com - Added a fix to the TRBE driver handling of sink_specific data - Added more description and ASCII art for overwrite in FILL mode work around - Added another TRBE erratum to the list. "TRBE may write to out-of-range address" Patches from 12-17 - Added comment to list the expectations around TSB erratum workaround. Suzuki K Poulose (16): for arm64 tree arm64: Add Neoverse-N2, Cortex-A710 CPU part definition arm64: errata: Add detection for TRBE overwrite in FILL mode arm64: errata: Add workaround for TSB flush failures arm64: errata: Add detection for TRBE write to out-of-range for CoreSight tree coresight: trbe: Add a helper to calculate the trace generated coresight: trbe: Add a helper to pad a given buffer area coresight: trbe: Decouple buffer base from the hardware base coresight: trbe: Allow driver to choose a different alignment coresight: trbe: Add infrastructure for Errata handling coresight: trbe: Workaround TRBE errata overwrite in FILL mode coresight: trbe: Add a helper to determine the minimum buffer size coresight: trbe: Make sure we have enough space coresight: trbe: Work around write to out of range arm64: errata: Advertise workaround for TRBE overwrite in FILL mode arm64: errata: Advertise the workaround for TSB flush failures arm64: errata: Advertise TRBE erratum workaround for write to out-of-range address Documentation/arm64/silicon-errata.rst | 12 + arch/arm64/Kconfig | 109 ++++++ arch/arm64/include/asm/barrier.h | 16 +- arch/arm64/include/asm/cputype.h | 4 + arch/arm64/kernel/cpu_errata.c | 64 ++++ arch/arm64/tools/cpucaps | 3 + drivers/hwtracing/coresight/coresight-trbe.c | 382 +++++++++++++++++-- 7 files changed, 554 insertions(+), 36 deletions(-) -- 2.25.4

5 years, 1 month

Re: [PATCH v2 00/17] arm64: Self-hosted trace related errata workarounds

by Suzuki K Poulose

On 08/10/2021 10:52, Will Deacon wrote: > On Fri, Oct 08, 2021 at 10:25:03AM +0100, Suzuki K Poulose wrote: >> Hi Will >> >> On 08/10/2021 08:32, Will Deacon wrote: >>> Hi Suzuki, >>> >>> On Tue, Sep 21, 2021 at 02:41:04PM +0100, Suzuki K Poulose wrote: >>>> This series adds CPU erratum work arounds related to the self-hosted >>>> tracing. The list of affected errata handled in this series are : >>>> >>>> * TRBE may overwrite trace in FILL mode >>>> - Arm Neoverse-N2 #2139208 >>>> - Cortex-A710 #211985 >>>> >>>> * A TSB instruction may not flush the trace completely when executed >>>> in trace prohibited region. >>>> >>>> - Arm Neoverse-N2 #2067961 >>>> - Cortex-A710 #2054223 >>>> >>>> * TRBE may write to out-of-range address >>>> - Arm Neoverse-N2 #2253138 >>>> - Cortex-A710 #2224489 >>>> >>>> The series applies on the self-hosted/trbe fixes posted here [0]. >>>> A tree containing both the series is available here [1] >>> >>> Any chance you could put the arch/arm64/ bits at the start of the series, >>> please? That way, I can queue them on their own branch which can be shared >>> with the coresight tree. >> >> I could move the bits around. I have a question though. >> >> Will, Catalin, Mathieu, >> >> The workaround for these errata, at least two of them are >> in the TRBE driver patches. Are we happy with enabling the Kconfig >> entry in the kernel, without the CoreSight patches to implement the work >> around ? > > I suppose you could move all the Kconfig changes into their own patch and > stick it right at the end in the Coresight tree. Cool, I will do that then. Thanks. I will send the updated series. Suzuki

5 years, 1 month

Re: [PATCH v2 00/17] arm64: Self-hosted trace related errata workarounds

by Suzuki K Poulose

Hi Will On 08/10/2021 08:32, Will Deacon wrote: > Hi Suzuki, > > On Tue, Sep 21, 2021 at 02:41:04PM +0100, Suzuki K Poulose wrote: >> This series adds CPU erratum work arounds related to the self-hosted >> tracing. The list of affected errata handled in this series are : >> >> * TRBE may overwrite trace in FILL mode >> - Arm Neoverse-N2 #2139208 >> - Cortex-A710 #211985 >> >> * A TSB instruction may not flush the trace completely when executed >> in trace prohibited region. >> >> - Arm Neoverse-N2 #2067961 >> - Cortex-A710 #2054223 >> >> * TRBE may write to out-of-range address >> - Arm Neoverse-N2 #2253138 >> - Cortex-A710 #2224489 >> >> The series applies on the self-hosted/trbe fixes posted here [0]. >> A tree containing both the series is available here [1] > > Any chance you could put the arch/arm64/ bits at the start of the series, > please? That way, I can queue them on their own branch which can be shared > with the coresight tree. I could move the bits around. I have a question though. Will, Catalin, Mathieu, The workaround for these errata, at least two of them are in the TRBE driver patches. Are we happy with enabling the Kconfig entry in the kernel, without the CoreSight patches to implement the work around ? Suzuki

5 years, 1 month

[PATCH v2 00/17] arm64: Self-hosted trace related errata workarounds

by Suzuki K Poulose

This series adds CPU erratum work arounds related to the self-hosted tracing. The list of affected errata handled in this series are : * TRBE may overwrite trace in FILL mode - Arm Neoverse-N2 #2139208 - Cortex-A710 #211985 * A TSB instruction may not flush the trace completely when executed in trace prohibited region. - Arm Neoverse-N2 #2067961 - Cortex-A710 #2054223 * TRBE may write to out-of-range address - Arm Neoverse-N2 #2253138 - Cortex-A710 #2224489 The series applies on the self-hosted/trbe fixes posted here [0]. A tree containing both the series is available here [1] [0] https://lkml.kernel.org/r/20210914102641.1852544-1-suzuki.poulose@arm.com [1] git@git.gitlab.arm.com:linux-arm/linux-skp.git coresight/errata/trbe-tsb-n2-a710/v2 Changes since v1: https://lkml.kernel.org/r/20210728135217.591173-1-suzuki.poulose@arm.com - Added a fix to the TRBE driver handling of sink_specific data - Added more description and ASCII art for overwrite in FILL mode work around - Added another TRBE erratum to the list. "TRBE may write to out-of-range address" Patches from 12-17 - Added comment to list the expectations around TSB erratum workaround. Suzuki K Poulose (17): coresight: trbe: Fix incorrect access of the sink specific data coresight: trbe: Add infrastructure for Errata handling coresight: trbe: Add a helper to calculate the trace generated coresight: trbe: Add a helper to pad a given buffer area coresight: trbe: Decouple buffer base from the hardware base coresight: trbe: Allow driver to choose a different alignment arm64: Add Neoverse-N2, Cortex-A710 CPU part definition arm64: Add erratum detection for TRBE overwrite in FILL mode coresight: trbe: Workaround TRBE errata overwrite in FILL mode arm64: Enable workaround for TRBE overwrite in FILL mode arm64: errata: Add workaround for TSB flush failures coresight: trbe: Add a helper to fetch cpudata from perf handle coresight: trbe: Add a helper to determine the minimum buffer size coresight: trbe: Make sure we have enough space arm64: Add erratum detection for TRBE write to out-of-range coresight: trbe: Work around write to out of range arm64: Advertise TRBE erratum workaround for write to out-of-range address Documentation/arm64/silicon-errata.rst | 12 + arch/arm64/Kconfig | 109 ++++++ arch/arm64/include/asm/barrier.h | 16 +- arch/arm64/include/asm/cputype.h | 4 + arch/arm64/kernel/cpu_errata.c | 64 ++++ arch/arm64/tools/cpucaps | 3 + drivers/hwtracing/coresight/coresight-trbe.c | 339 +++++++++++++++++-- 7 files changed, 510 insertions(+), 37 deletions(-) -- 2.24.1

5 years, 1 month

[PATCH v2 00/12] OpenCSD: v1.2.0: Update to add decode statistics API.

by Mike Leach

Adds a generic API to allow packet processors to count the amount of bytes per channel processed and not synced plus any packet header or format errors. The ETMv4 / ETE packet processor is updated to use this API. Statistics are also provided for the CoreSight frame demux, which are global across all channels. Typical output from trc_pkt_lister when run with -stats option to print stats: =============================================================== Trace Packet Lister : Trace buffer done, processed 65536 bytes. Reading packet decoder statistics.... Decode stats ID 0x10 Total Bytes: 55273; Unsynced Bytes: 1453 Bad Header Errors: 0; Bad Sequence Errors: 0 Decode stats ID 0x11 Total Bytes: 672; Unsynced Bytes: 132 Bad Header Errors: 0; Bad Sequence Errors: 0 Decode stats ID 0x12 Total Bytes: 672; Unsynced Bytes: 648 Bad Header Errors: 0; Bad Sequence Errors: 0 Decode stats ID 0x13 Total Bytes: 698; Unsynced Bytes: 0 Bad Header Errors: 0; Bad Sequence Errors: 0 Decode stats ID 0x14 Total Bytes: 0; Unsynced Bytes: 0 Bad Header Errors: 0; Bad Sequence Errors: 0 Decode stats ID 0x15 Total Bytes: 2783; Unsynced Bytes: 471 Bad Header Errors: 0; Bad Sequence Errors: 0 Frame Demux Stats Trace data bytes sent to registered ID decoders: 60098 Trace data bytes without registered ID decoders: 0 Trace data bytes with unknown ID: 81 Trace data bytes with reserved ID: 22 Frame demux bytes, ID bytes and sync bytes: 5335 Total bytes processed by frame demux: 65536 ================================================================ API adds ocsd_decode_stats_t structure to contain the statistics. (ocsd_if_types.h) C-API (ocsd_c_apo.h) adds functions:- ocsd_dt_get_decode_stats() - get pointer to stats block. ocsd_dt_reset_decode_stats() - resets the counts to zero. This function operates independently of the main decoder reset. This allows for tools such as perf which may reset the decoder multiple times per AUXTRACE_BUFFER to count stats for the entire buffer rather than each capture block. Changes since v1: 1) stats structure now contains a block for frame demux data. 2) patchset contains a number of additional build and code fixes that will be included in the 1.2.0 release. James Clark (1): opencsd: Remove noisy printf Mike Leach (10): opencsd: Add decode statistics API to packet processor. opencsd: ETMv4: ETE: Add packet processing stats to decoders. tests: Update test programs to use the packet decoder statistics API build: tests: Fix build warnings in snapshot parser. build: tests: Fix build warnings in mem_buff_demo test build: tests: Fix build warnings in C-API test program opencsd: stats: Add collection of CoreSight frame demux stats tests: Add printing of CS frame Demux stats to test program. tests: Update test scripts to pass additional options opencsd: Update readme and version info for v1.2.0 Yi Kong (1): opencsd: build: Remove unused variable README.md | 9 ++- decoder/include/common/ocsd_dcd_tree.h | 29 ++++++++- .../include/common/trc_frame_deformatter.h | 4 ++ decoder/include/common/trc_pkt_proc_base.h | 47 +++++++++++++- decoder/include/opencsd/c_api/opencsd_c_api.h | 30 ++++++++- decoder/include/opencsd/ocsd_if_types.h | 47 ++++++++++++++ decoder/include/opencsd/ocsd_if_version.h | 6 +- decoder/source/c_api/ocsd_c_api.cpp | 18 +++++- decoder/source/etmv4/trc_pkt_proc_etmv4i.cpp | 10 ++- decoder/source/ocsd_dcd_tree.cpp | 64 +++++++++++++++++++ decoder/source/trc_frame_deformatter.cpp | 60 +++++++++++++++-- decoder/source/trc_frame_deformatter_impl.h | 14 +++- decoder/source/trc_printable_elem.cpp | 2 - decoder/tests/run_pkt_decode_single.bash | 7 +- decoder/tests/run_pkt_decode_tests-ete.bash | 11 ++-- decoder/tests/run_pkt_decode_tests.bash | 17 +++-- .../include/snapshot_parser.h | 6 +- .../source/snapshot_parser.cpp | 4 ++ decoder/tests/source/c_api_pkt_print_test.c | 39 ++++++++++- decoder/tests/source/mem_buff_demo.cpp | 9 ++- decoder/tests/source/trc_pkt_lister.cpp | 63 +++++++++++++++++- 21 files changed, 455 insertions(+), 41 deletions(-) -- 2.17.1

5 years, 1 month

Re: [PATCH] coresight: etm4x: avoid build failure with unrolled loops

by Suzuki K Poulose

Hi Tao On 26/09/2021 11:35, Tao Zhang wrote: > clang-12 fails to build the etm4x driver with -fsanitize=array-bounds, > where it decides to unroll certain loops in a way that result in a > C variable getting put into an inline assembly. > > Search this build failure and find this is a known issue and there > has been a mail thread discussing it. > https://patchwork.kernel.org/project/linux-arm-kernel/patch/20210429145752.… > According to the modification suggestions of this mail thread, > coresight infrastucture has already provided another API that > can replace the function that caused the error. > > Used here "csdev_access_read32" to replace the original API > "etm4x_relaxed_read32". > > This patch applies to coresight/next > https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git > > Signed-off-by: Tao Zhang <quic_taozha(a)quicinc.com> Thanks for picking up the patch. Please could you convert all the other variable indexed register access too ? That would save us spinning up patches for fixing those individual cases whenever the compiler decides to change its behavior. Suzuki

5 years, 1 month

Re: [PATCH] coresight: etm4x: avoid build failure with unrolled loops

by Mathieu Poirier

Hi Tao, On Sun, Sep 26, 2021 at 06:35:50PM +0800, Tao Zhang wrote: > clang-12 fails to build the etm4x driver with -fsanitize=array-bounds, > where it decides to unroll certain loops in a way that result in a > C variable getting put into an inline assembly. > > Search this build failure and find this is a known issue and there > has been a mail thread discussing it. > https://patchwork.kernel.org/project/linux-arm-kernel/patch/20210429145752.… > According to the modification suggestions of this mail thread, > coresight infrastucture has already provided another API that > can replace the function that caused the error. > > Used here "csdev_access_read32" to replace the original API > "etm4x_relaxed_read32". > > This patch applies to coresight/next > https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git > > Signed-off-by: Tao Zhang <quic_taozha(a)quicinc.com> > --- > drivers/hwtracing/coresight/coresight-etm4x-core.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c > index f58afbab6e6d..0bca8e2be070 100644 > --- a/drivers/hwtracing/coresight/coresight-etm4x-core.c > +++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c > @@ -797,7 +797,7 @@ static void etm4_disable_hw(void *info) > /* read back the current counter values */ > for (i = 0; i < drvdata->nr_cntr; i++) { > config->cntr_val[i] = > - etm4x_relaxed_read32(csa, TRCCNTVRn(i)); > + csdev_access_read32(csa, TRCCNTVRn(i)); It seems like the patch you are referencing above was never applied... So the question is, how is it that only this instance is giving you trouble when there are many more instances of the same pattern in the file? Thanks, Mathieu > } > > coresight_disclaim_device_unlocked(csdev); > -- > The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, > a Linux Foundation Collaborative Project >

5 years, 1 month

Re: [PATCH v2 09/17] coresight: trbe: Workaround TRBE errata overwrite in FILL mode

by Suzuki K Poulose

On 23/09/2021 07:13, Anshuman Khandual wrote: > > > On 9/21/21 7:11 PM, Suzuki K Poulose wrote: >> ARM Neoverse-N2 (#2139208) and Cortex-A710(##2119858) suffers from >> an erratum, which when triggered, might cause the TRBE to overwrite >> the trace data already collected in FILL mode, in the event of a WRAP. >> i.e, the TRBE doesn't stop writing the data, instead wraps to the base >> and could write upto 3 cache line size worth trace. Thus, this could >> corrupt the trace at the "BASE" pointer. >> >> The workaround is to program the write pointer 256bytes from the > > 3 cache lines = 256 bytes on all implementation which might have TRBE ? > OR this skid bytes should be derived from the platform cache line size > instead. 256bytes is the aligned (to the power of 2) value for the safe guard. Not 3 cache lines. Ideally, if there is another CPU that has larger cache line size, affected by the erratum, yes, we must do that. But for now this is sufficient. > >> base, such that if the erratum is triggered, it doesn't overwrite >> the trace data that was captured. This skipped region could be >> padded with ignore packets at the end of the session, so that >> the decoder sees a continuous buffer with some padding at the >> beginning. The trace data written at the base is considered >> lost as the limit could have been in the middle of the perf >> ring buffer, and jumping to the "base" is not acceptable. >> We set the flags already to indicate that some amount of trace >> was lost during the FILL event IRQ. So this is fine. > > Via PERF_AUX_FLAG_TRUNCATED ? Should be specified here to be clear. Please note that setting the flag is not a side effect of the work around. And as such I don't think this needs to be mentioned here. e.g, we changed this to COLLISION recently for WRAP events. It makes sense to keep the details to the driver. > >> >> One important change with the work around is, we program the >> TRBBASER_EL1 to current page where we are allowed to write. >> Otherwise, it could overwrite a region that may be consumed >> by the perf. Towards this, we always make sure that the >> "handle->head" and thus the trbe_write is PAGE_SIZE aligned, >> so that we can set the BASE to the PAGE base and move the >> TRBPTR to the 256bytes offset. >> >> Cc: Mike Leach <mike.leach(a)linaro.org> >> Cc: Mathieu Poirier <mathieu.poirier(a)linaro.org> >> Cc: Anshuman Khandual <anshuman.khandual(a)arm.com> >> Cc: Leo Yan <leo.yan(a)linaro.org> >> Signed-off-by: Suzuki K Poulose <suzuki.poulose(a)arm.com> >> --- >> Change since v1: >> - Updated comment with ASCII art >> - Add _BYTES suffix for the space to skip for the work around. >> --- >> drivers/hwtracing/coresight/coresight-trbe.c | 144 +++++++++++++++++-- >> 1 file changed, 132 insertions(+), 12 deletions(-) >> >> diff --git a/drivers/hwtracing/coresight/coresight-trbe.c b/drivers/hwtracing/coresight/coresight-trbe.c >> index f569010c672b..983dd5039e52 100644 >> --- a/drivers/hwtracing/coresight/coresight-trbe.c >> +++ b/drivers/hwtracing/coresight/coresight-trbe.c >> @@ -16,6 +16,7 @@ >> #define pr_fmt(fmt) DRVNAME ": " fmt >> >> #include <asm/barrier.h> >> +#include <asm/cpufeature.h> >> #include <asm/cputype.h> >> >> #include "coresight-self-hosted-trace.h" >> @@ -84,9 +85,17 @@ struct trbe_buf { >> * per TRBE instance, we keep track of the list of errata that >> * affects the given instance of the TRBE. >> */ >> -#define TRBE_ERRATA_MAX 0 >> +#define TRBE_WORKAROUND_OVERWRITE_FILL_MODE 0 >> +#define TRBE_ERRATA_MAX 1 >> + >> +/* >> + * Safe limit for the number of bytes that may be overwritten >> + * when the erratum is triggered. >> + */ >> +#define TRBE_WORKAROUND_OVERWRITE_FILL_MODE_SKIP_BYTES 256 > > As mentioned earlier, does it depend on the platform cache line size ? > Otherwise if the skip bytes is something platform independent, should > be mentioned here in a comment. I could add in a comment. > >> >> static unsigned long trbe_errata_cpucaps[TRBE_ERRATA_MAX] = { >> + [TRBE_WORKAROUND_OVERWRITE_FILL_MODE] = ARM64_WORKAROUND_TRBE_OVERWRITE_FILL_MODE, >> }; >> >> /* >> @@ -519,10 +528,13 @@ static void trbe_enable_hw(struct trbe_buf *buf) >> set_trbe_limit_pointer_enabled(buf->trbe_limit); >> } >> >> -static enum trbe_fault_action trbe_get_fault_act(u64 trbsr) >> +static enum trbe_fault_action trbe_get_fault_act(struct perf_output_handle *handle, >> + u64 trbsr) >> { >> int ec = get_trbe_ec(trbsr); >> int bsc = get_trbe_bsc(trbsr); >> + struct trbe_buf *buf = etm_perf_sink_config(handle); >> + struct trbe_cpudata *cpudata = buf->cpudata; > > Passing down the perf handle to derive trbe_cpudata seems to be right. > >> >> WARN_ON(is_trbe_running(trbsr)); >> if (is_trbe_trg(trbsr) || is_trbe_abort(trbsr)) >> @@ -531,10 +543,16 @@ static enum trbe_fault_action trbe_get_fault_act(u64 trbsr) >> if ((ec == TRBE_EC_STAGE1_ABORT) || (ec == TRBE_EC_STAGE2_ABORT)) >> return TRBE_FAULT_ACT_FATAL; >> >> - if (is_trbe_wrap(trbsr) && (ec == TRBE_EC_OTHERS) && (bsc == TRBE_BSC_FILLED)) { >> - if (get_trbe_write_pointer() == get_trbe_base_pointer()) >> - return TRBE_FAULT_ACT_WRAP; >> - } >> + /* >> + * If the trbe is affected by TRBE_WORKAROUND_OVERWRITE_FILL_MODE, >> + * it might write data after a WRAP event in the fill mode. >> + * Thus the check TRBPTR == TRBBASER will not be honored. >> + */ > > Needs bit formatting/alignment cleanup. > >> + if ((is_trbe_wrap(trbsr) && (ec == TRBE_EC_OTHERS) && (bsc == TRBE_BSC_FILLED)) && >> + (trbe_has_erratum(cpudata, TRBE_WORKAROUND_OVERWRITE_FILL_MODE) || >> + get_trbe_write_pointer() == get_trbe_base_pointer())) >> + return TRBE_FAULT_ACT_WRAP; >> + > > Right, TRBE without the errata should continue to have the write > pointer = base pointer check. Could all TRBE errata checks like > the following be shortened (without the workaround index) for > better readability ? But not something very important. > > trbe_has_erratum(cpudata, TRBE_WORKAROUND_OVERWRITE_FILL_MODE) Do you mean something like : trbe_has_erratum(cpudata, TRBE_WORKAROUND_OVERWRITE_FILL_MODE) -> trbe_may_overwrite_in_fill_mode(cpudata) ? > > >> return TRBE_FAULT_ACT_SPURIOUS; >> } >> >> @@ -544,6 +562,8 @@ static unsigned long trbe_get_trace_size(struct perf_output_handle *handle, >> { >> u64 write; >> u64 start_off, end_off; >> + u64 size; >> + u64 overwrite_skip = TRBE_WORKAROUND_OVERWRITE_FILL_MODE_SKIP_BYTES; >> >> /* >> * If the TRBE has wrapped around the write pointer has >> @@ -559,7 +579,18 @@ static unsigned long trbe_get_trace_size(struct perf_output_handle *handle, >> >> if (WARN_ON_ONCE(end_off < start_off)) >> return 0; >> - return (end_off - start_off); >> + >> + size = end_off - start_off; >> + /* >> + * If the TRBE is affected by the following erratum, we must fill >> + * the space we skipped with IGNORE packets. And we are always >> + * guaranteed to have at least a PAGE_SIZE space in the buffer. >> + */ >> + if (trbe_has_erratum(buf->cpudata, TRBE_WORKAROUND_OVERWRITE_FILL_MODE) && >> + !WARN_ON(size < overwrite_skip)) >> + __trbe_pad_buf(buf, start_off, overwrite_skip); >> + >> + return size; >> } >> >> static void *arm_trbe_alloc_buffer(struct coresight_device *csdev, >> @@ -678,7 +709,7 @@ static unsigned long arm_trbe_update_buffer(struct coresight_device *csdev, >> clr_trbe_irq(); >> isb(); >> >> - act = trbe_get_fault_act(status); >> + act = trbe_get_fault_act(handle, status); >> /* >> * If this was not due to a WRAP event, we have some >> * errors and as such buffer is empty. >> @@ -702,21 +733,95 @@ static unsigned long arm_trbe_update_buffer(struct coresight_device *csdev, >> return size; >> } >> >> + >> +static int trbe_apply_work_around_before_enable(struct trbe_buf *buf) >> +{ >> + /* >> + * TRBE_WORKAROUND_OVERWRITE_FILL_MODE causes the TRBE to overwrite a few cache > > few cache lines = 3 cache lines ? Yes, upto 3. > >> + * line size from the "TRBBASER_EL1" in the event of a "FILL". >> + * Thus, we could loose some amount of the trace at the base. >> + * >> + * Before Fix: >> + * >> + * normal-BASE head normal-PTR tail normal-LIMIT >> + * | \/ / >> + * ------------------------------------------------------------- >> + * | | |xyzdefghij..|... tuvw| | >> + * ------------------------------------------------------------- >> + * / | \ >> + * After Fix-> TRBBASER TRBPTR TRBLIMITR.LIMIT >> + * >> + * In the normal course of action, we would set the TRBBASER to the >> + * beginning of the ring-buffer (normal-BASE). But with the erratum, >> + * the TRBE could overwrite the contents at the "normal-BASE", after >> + * hitting the "normal-LIMIT", since it doesn't stop as expected. And >> + * this is wrong. So we must always make sure that the TRBBASER is >> + * within the region [head, head+size]. >> + * >> + * Also, we would set the TRBPTR to head (after adjusting for >> + * alignment) at normal-PTR. This would mean that the last few bytes >> + * of the trace (say, "xyz") might overwrite the first few bytes of >> + * trace written ("abc"). More importantly they will appear in what\ >> + * userspace sees as the beginning of the trace, which is wrong. We may >> + * not always have space to move the latest trace "xyz" to the correct >> + * order as it must appear beyond the LIMIT. (i.e, [head..head+size]. >> + * Thus it is easier to ignore those bytes than to complicate the >> + * driver to move it, assuming that the erratum was triggered and doing >> + * additional checks to see if there is indeed allowed space at >> + * TRBLIMITR.LIMIT. >> + * >> + * To summarize, with the work around: >> + * >> + * - We always align the offset for the next session to PAGE_SIZE >> + * (This is to ensure we can program the TRBBASER to this offset >> + * within the region [head...head+size]). >> + * >> + * - At TRBE enable: >> + * - Set the TRBBASER to the page aligned offset of the current >> + * proposed write offset. (which is guaranteed to be aligned >> + * as above) >> + * - Move the TRBPTR to skip first 256bytes (that might be >> + * overwritten with the erratum). This ensures that the trace >> + * generated in the session is not re-written. >> + * >> + * - At trace collection: >> + * - Pad the 256bytes skipped above again with IGNORE packets. >> + */ >> + if (trbe_has_erratum(buf->cpudata, TRBE_WORKAROUND_OVERWRITE_FILL_MODE)) { >> + if (WARN_ON(!IS_ALIGNED(buf->trbe_write, PAGE_SIZE))) >> + return -EINVAL; >> + buf->trbe_hw_base = buf->trbe_write; >> + buf->trbe_write += TRBE_WORKAROUND_OVERWRITE_FILL_MODE_SKIP_BYTES; >> + } >> + >> + return 0; >> +} >> + >> static int __arm_trbe_enable(struct trbe_buf *buf, >> struct perf_output_handle *handle) >> { >> + int ret = 0; >> + >> perf_aux_output_flag(handle, PERF_AUX_FLAG_CORESIGHT_FORMAT_RAW); >> buf->trbe_limit = compute_trbe_buffer_limit(handle); >> buf->trbe_write = buf->trbe_base + PERF_IDX2OFF(handle->head, buf); >> if (buf->trbe_limit == buf->trbe_base) { >> - trbe_stop_and_truncate_event(handle); >> - return -ENOSPC; >> + ret = -ENOSPC; >> + goto err; >> } >> /* Set the base of the TRBE to the buffer base */ >> buf->trbe_hw_base = buf->trbe_base; >> + >> + ret = trbe_apply_work_around_before_enable(buf); >> + if (ret) >> + goto err; >> + >> *this_cpu_ptr(buf->cpudata->drvdata->handle) = handle; >> trbe_enable_hw(buf); >> return 0; >> +err: >> + trbe_stop_and_truncate_event(handle); >> + return ret; >> } >> >> static int arm_trbe_enable(struct coresight_device *csdev, u32 mode, void *data) >> @@ -860,7 +965,7 @@ static irqreturn_t arm_trbe_irq_handler(int irq, void *dev) >> if (!is_perf_trbe(handle)) >> return IRQ_NONE; >> >> - act = trbe_get_fault_act(status); >> + act = trbe_get_fault_act(handle, status); >> switch (act) { >> case TRBE_FAULT_ACT_WRAP: >> truncated = !!trbe_handle_overflow(handle); >> @@ -1000,7 +1105,22 @@ static void arm_trbe_probe_cpu(void *info) >> } >> >> trbe_check_errata(cpudata); >> - cpudata->trbe_align = cpudata->trbe_hw_align; >> + /* >> + * If the TRBE is affected by erratum TRBE_WORKAROUND_OVERWRITE_FILL_MODE, >> + * we must always program the TBRPTR_EL1, 256bytes from a page >> + * boundary, with TRBBASER_EL1 set to the page, to prevent >> + * TRBE over-writing 256bytes at TRBBASER_EL1 on FILL event. >> + * >> + * Thus make sure we always align our write pointer to a PAGE_SIZE, >> + * which also guarantees that we have at least a PAGE_SIZE space in >> + * the buffer (TRBLIMITR is PAGE aligned) and thus we can skip >> + * the required bytes at the base. >> + */ >> + if (trbe_has_erratum(cpudata, TRBE_WORKAROUND_OVERWRITE_FILL_MODE)) >> + cpudata->trbe_align = PAGE_SIZE; >> + else >> + cpudata->trbe_align = cpudata->trbe_hw_align; >> + > > But like trbe_apply_work_around_before_enable(), trbe_align assignment > should also be wrapped inside a new helper which should contain these > comments and conditional block. Because it makes sense to have errata > work arounds in the leaf level helper functions, rather than TRBE core > operations. That would imply we re-initialize the trbe_align in the new helper after setting the value here for all other unaffected TRBEs. I would rather leave it as it is, until we have more work arounds that touch this area. This is one of code called per TRBE instance. Suzuki

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