mainlining shenanigans
93929fb6c4
A patch series from Sai Prakash Ranjan, who explains:
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 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/
Link: https://lore.kernel.org/lkml/cover.1652891705.git.quic_saipraka@quicinc.com/
* asm-generic-mmiotrace:
soc: qcom: geni: Disable MMIO tracing for GENI SE
serial: qcom_geni_serial: Disable MMIO tracing for geni serial
asm-generic/io: Add logging support for MMIO accessors
KVM: arm64: Add a flag to disable MMIO trace for nVHE KVM
lib: Add register read/write tracing support
drm/meson: Fix overflow implicit truncation warnings
irqchip/tegra: Fix overflow implicit truncation warnings
coresight: etm4x: Use asm-generic IO memory barriers
arm64: io: Use asm-generic high level MMIO accessors
arch/*: Disable softirq stacks on PREEMPT_RT.
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Linux kernel
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