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Date: Thu, 21 Apr 2022 07:30:19 +0530 From: Sai Prakash Ranjan <quic_saipraka@...cinc.com> To: <arnd@...db.de> CC: <catalin.marinas@....com>, <gregkh@...uxfoundation.org>, <linux-arm-kernel@...ts.infradead.org>, <linux-arm-msm@...r.kernel.org>, <linux-kernel@...r.kernel.org>, <maz@...nel.org>, <quic_psodagud@...cinc.com>, <quic_tsoni@...cinc.com>, <rostedt@...dmis.org>, <will@...nel.org> Subject: Re: [PATCHv10 0/6] lib/rwmmio/arm64: Add support to trace register reads/writes Hi Arnd, On 4/8/2022 4:47 PM, Sai Prakash Ranjan wrote: > Hi Arnd, > > On 2/24/2022 11:37 AM, Sai Prakash Ranjan wrote: >> Generic MMIO read/write i.e., __raw_{read,write}{b,l,w,q} accessors >> are typically used to read/write from/to memory mapped registers >> and can cause hangs or some undefined behaviour in following cases, >> >> * If the access to the register space is unclocked, for example: if >> there is an access to multimedia(MM) block registers without MM >> clocks. >> >> * If the register space is protected and not set to be accessible from >> non-secure world, for example: only EL3 (EL: Exception level) access >> is allowed and any EL2/EL1 access is forbidden. >> >> * If xPU(memory/register protection units) is controlling access to >> certain memory/register space for specific clients. >> >> and more... >> >> Such cases usually results in instant reboot/SErrors/NOC or interconnect >> hangs and tracing these register accesses can be very helpful to debug >> such issues during initial development stages and also in later stages. >> >> So use ftrace trace events to log such MMIO register accesses which >> provides rich feature set such as early enablement of trace events, >> filtering capability, dumping ftrace logs on console and many more. >> >> Sample output: >> >> rwmmio_write: __qcom_geni_serial_console_write+0x160/0x1e0 width=32 val=0xa0d5d addr=0xfffffbfffdbff700 >> rwmmio_post_write: __qcom_geni_serial_console_write+0x160/0x1e0 width=32 val=0xa0d5d addr=0xfffffbfffdbff700 >> rwmmio_read: qcom_geni_serial_poll_bit+0x94/0x138 width=32 addr=0xfffffbfffdbff610 >> rwmmio_post_read: qcom_geni_serial_poll_bit+0x94/0x138 width=32 val=0x0 addr=0xfffffbfffdbff610 >> >> This series is a follow-up for the series [1] and a recent series [2] making use >> of both. >> >> [1] https://lore.kernel.org/lkml/cover.1536430404.git.saiprakash.ranjan@codeaurora.org/ >> [2] https://lore.kernel.org/lkml/1604631386-178312-1-git-send-email-psodagud@codeaurora.org/ >> >> Note in previous v4 version, Arnd suggested to benchmark and compare size with callback >> based implementation, please see [3] for more details on that with brief comparison below. >> >> >> **Inline version with CONFIG_FTRACE=y and CONFIG_TRACE_MMIO_ACCESS=y** >> $ size vmlinux >> text data bss dec hex filename >> 23884219 14284468 532568 38701255 24e88c7 vmlinux >> >> **Callback version with CONFIG_FTRACE=y and CONFIG_TRACE_MMIO_ACCESS=y** >> $ size vmlinux >> text data bss dec hex filename >> 24108179 14279596 532568 38920343 251e097 vmlinux >> >> $ ./scripts/bloat-o-meter inline-vmlinux callback-vmlinux >> add/remove: 8/3 grow/shrink: 4889/89 up/down: 242244/-11564 (230680) >> Total: Before=25812612, After=26043292, chg +0.89% >> >> [3] https://lore.kernel.org/lkml/466449a1-36da-aaa9-7e4f-477f36b52c9e@quicinc.com/ >> >> Changes in v10: >> * Use GENMASK(31, 0) for -Woverflow warning in irqchip tegra driver (Marc). >> * Convert ETM4x ARM64 driver to use asm-generic IO memory barriers (Catalin). >> * Collect ack from Catalin for arm64 change. >> >> Changes in v9: >> * Use TRACE_EVENT_CLASS for rwmmio_write and post_write (Steven Rostedt). >> >> Changes in v8: >> * Fix build error reported by kernel test robot. >> >> Changes in v7: >> * Use lib/ instead of kernel/trace/ based on review comment by Steven Rostedt. >> >> Changes in v6: >> * Implemented suggestions by Arnd Bergmann: >> - Use arch independent IO barriers in arm64/asm >> - Add ARCH_HAVE_TRACE_MMIO_ACCESS >> - Add post read and post write logging support >> - Remove tracepoint_active check >> * Fix build error reported by kernel test robot. >> >> Changes in v5: >> * Move arm64 to use asm-generic provided high level MMIO accessors (Arnd). >> * Add inline logging for MMIO relaxed and non-relaxed accessors. >> * Move nVHE KVM comment to makefile (Marc). >> * Fix overflow warning due to switch to inline accessors instead of macro. >> * Modify trace event field to include caller and parent details for more detailed logs. >> >> Changes in v4: >> * Drop dynamic debug based filter support since that will be developed later with >> the help from Steven (Ftrace maintainer). >> * Drop value passed to writel as it is causing hangs when tracing is enabled. >> * Code cleanup for trace event as suggested by Steven for earlier version. >> * Fixed some build errors reported by 0-day bot. >> >> Changes in v3: >> * Create a generic mmio header for instrumented version (Earlier suggested in [1] >> by Will Deacon and recently [2] by Greg to have a generic version first). >> * Add dynamic debug support to filter out traces which can be very useful for targeted >> debugging specific to subsystems or drivers. >> * Few modifications to the rwmmio trace event fields to include the mmio width and print >> addresses in hex. >> * Rewrote commit msg to explain some more about usecases. >> >> Prasad Sodagudi (1): >> lib: Add register read/write tracing support >> >> Sai Prakash Ranjan (5): >> arm64: io: Use asm-generic high level MMIO accessors >> coresight: etm4x: Use asm-generic IO memory barriers >> irqchip/tegra: Fix overflow implicit truncation warnings >> drm/meson: Fix overflow implicit truncation warnings >> asm-generic/io: Add logging support for MMIO accessors >> >> arch/Kconfig | 3 + >> arch/arm64/Kconfig | 1 + >> arch/arm64/include/asm/io.h | 41 ++------ >> arch/arm64/kvm/hyp/nvhe/Makefile | 7 +- >> drivers/gpu/drm/meson/meson_viu.c | 22 ++--- >> .../coresight/coresight-etm4x-core.c | 8 +- >> drivers/hwtracing/coresight/coresight-etm4x.h | 8 +- >> drivers/irqchip/irq-tegra.c | 10 +- >> include/asm-generic/io.h | 82 +++++++++++++++- >> include/trace/events/rwmmio.h | 97 +++++++++++++++++++ >> lib/Kconfig | 7 ++ >> lib/Makefile | 2 + >> lib/trace_readwrite.c | 47 +++++++++ >> 13 files changed, 273 insertions(+), 62 deletions(-) >> create mode 100644 include/trace/events/rwmmio.h >> create mode 100644 lib/trace_readwrite.c >> >> >> base-commit: 754e0b0e35608ed5206d6a67a791563c631cec07 > Gentle ping, could you please take a look at this, would appreciate your reviews. > Gentle Ping !! Thanks, Sai
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