Messages in this thread | | | Date | Mon, 3 Jan 2022 11:11:03 +0530 | Subject | Re: [PATCHv6 0/5] tracing/rwmmio/arm64: Add support to trace register reads/writes | From | Sai Prakash Ranjan <> |
| |
On 12/13/2021 8:58 AM, Sai Prakash Ranjan wrote: > Hi Arnd, > > On 12/7/2021 12:24 PM, 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 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): >> tracing: Add register read/write tracing support >> >> Sai Prakash Ranjan (4): >> arm64: io: Use asm-generic high level MMIO accessors >> 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 +++--- >> drivers/irqchip/irq-tegra.c | 10 +-- >> include/asm-generic/io.h | 81 +++++++++++++++++++-- >> include/trace/events/rwmmio.h | 112 ++++++++++++++++++++++++++++++ >> kernel/trace/Kconfig | 7 ++ >> kernel/trace/Makefile | 1 + >> kernel/trace/trace_readwrite.c | 47 +++++++++++++ >> 11 files changed, 278 insertions(+), 54 deletions(-) >> create mode 100644 include/trace/events/rwmmio.h >> create mode 100644 kernel/trace/trace_readwrite.c >> > > Does this version look good to you? From the other mail thread it > seems Catalin > is ok with your suggested change. Kernel test robot hasn't come with > any build error > reports so far, I have fixed the previous reported one in meson drm > driver. > > Thanks, > Sai
Any more comments for this version?
Thanks, Sai
| |