From 4352b8aee98005853aa63f57d6377282de17a33f Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Sun, 23 Aug 2026 13:28:57 -0700 Subject: Merge tag 'i3c/for-7.3' of git://git.kernel.org/pub/scm/linux/kernel/git/i3c/linux Pull I3C updates from Alexandre Belloni: "A new driver this cycle, for the AMD AXI I3C controller. There are also new features such as IBI wakeup support, SETAASA device discovery and ACPI support for the the DAA methods, meaning we can now communicate with the SPD devices on DDR5 modules. New driver: - AMD AXI I3C master controller Subsystem: - I3C Common Command Code (CCC) handling improvements, especially around GET CCCs - SETAASA device discovery support - ACPI support for all existing DAA methods like SETDASA, SETNEWDA as well as I2C devices on I3C bus - IBI-based wakeup support Drivers: - dw: SETAASA support - mipi-i3c-hci: advertise IBI wakeup capability, AMD_PT I3C controller support, PIO queue management support for HCI v1.2 - renesas: improve suspend to RAM support, add runtime PM support" * tag 'i3c/for-7.3' of git://git.kernel.org/pub/scm/linux/kernel/git/i3c/linux: (70 commits) i3c: dw: reduce do_daa time if there's no client i3c: mipi-i3c-hci: Add support for AMD_PT I3C controller i3c: mipi-i3c-hci: Add PIO queue management support for HCI v1.2 i3c: mipi-i3c-hci: Fix missing STAT_IBI_STATUS_THLD in PIO mode i3c: dw: rename "pclk" to "apb" to match dt-binding i3c: dw: make struct dw_i3c_cmd smaller i3c: dw: use COMMAND_PORT_TRANSFER_ARG instead of hardcoding i3c: renesas: Don't register devices when ENTDAA times out i3c: master: dw-i3c-master: fix OD timing for first broadcast i3c: mipi-i3c-hci: Advertise IBI wakeup capability i3c: mipi-i3c-hci: Factor out i3c_hci_sysdev() i3c: mipi-i3c-hci-pci: Propagate I3C wakeup requirements to PCI i3c: master: Reject IBI requests from non-IBI-capable devices i3c: master: Add helper to query bus wakeup requirements i3c: master: Report wakeup events for IBIs i3c: master: Support IBI-based wakeup capability i3c: master: Fix potential UAF in i3c_device_match() i3c: master: Fix potential UAF in i3c_device_uevent() i3c: Make dev->desc locking assumptions explicit i3c: master: Fix use-after-free of master->this ... --- tools/virtio/virtio-trace/README | 118 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 118 insertions(+) create mode 100644 tools/virtio/virtio-trace/README (limited to 'tools/virtio/virtio-trace/README') diff --git a/tools/virtio/virtio-trace/README b/tools/virtio/virtio-trace/README new file mode 100644 index 000000000..0127ff0c5 --- /dev/null +++ b/tools/virtio/virtio-trace/README @@ -0,0 +1,118 @@ +Trace Agent for virtio-trace +============================ + +Trace agent is a user tool for sending trace data of a guest to a Host in low +overhead. Trace agent has the following functions: + - splice a page of ring-buffer to read_pipe without memory copying + - splice the page from write_pipe to virtio-console without memory copying + - write trace data to stdout by using -o option + - controlled by start/stop orders from a Host + +The trace agent operates as follows: + 1) Initialize all structures. + 2) Create a read/write thread per CPU. Each thread is bound to a CPU. + The read/write threads hold it. + 3) A controller thread does poll() for a start order of a host. + 4) After the controller of the trace agent receives a start order from a host, + the controller wake read/write threads. + 5) The read/write threads start to read trace data from ring-buffers and + write the data to virtio-serial. + 6) If the controller receives a stop order from a host, the read/write threads + stop to read trace data. + + +Files +===== + +README: this file +Makefile: Makefile of trace agent for virtio-trace +trace-agent.c: includes main function, sets up for operating trace agent +trace-agent.h: includes all structures and some macros +trace-agent-ctl.c: includes controller function for read/write threads +trace-agent-rw.c: includes read/write threads function + + +Setup +===== + +To use this trace agent for virtio-trace, we need to prepare some virtio-serial +I/Fs. + +1) Make FIFO in a host + virtio-trace uses virtio-serial pipe as trace data paths as to the number +of CPUs and a control path, so FIFO (named pipe) should be created as follows: + # mkdir /tmp/virtio-trace/ + # mkfifo /tmp/virtio-trace/trace-path-cpu{0,1,2,...,X}.{in,out} + # mkfifo /tmp/virtio-trace/agent-ctl-path.{in,out} + +For example, if a guest use three CPUs, the names are + trace-path-cpu{0,1,2}.{in.out} +and + agent-ctl-path.{in,out}. + +2) Set up of virtio-serial pipe in a host + Add qemu option to use virtio-serial pipe. + + ##virtio-serial device## + -device virtio-serial-pci,id=virtio-serial0\ + ##control path## + -chardev pipe,id=charchannel0,path=/tmp/virtio-trace/agent-ctl-path\ + -device virtserialport,bus=virtio-serial0.0,nr=1,chardev=charchannel0,\ + id=channel0,name=agent-ctl-path\ + ##data path## + -chardev pipe,id=charchannel1,path=/tmp/virtio-trace/trace-path-cpu0\ + -device virtserialport,bus=virtio-serial0.0,nr=2,chardev=charchannel1,\ + id=channel1,name=trace-path-cpu0\ + ... + +If you manage guests with libvirt, add the following tags to domain XML files. +Then, libvirt passes the same command option to qemu. + + + + +
+ + + + +
+ + ... +Here, chardev names are restricted to trace-path-cpuX and agent-ctl-path. For +example, if a guest use three CPUs, chardev names should be trace-path-cpu0, +trace-path-cpu1, trace-path-cpu2, and agent-ctl-path. + +3) Boot the guest + You can find some chardev in /dev/virtio-ports/ in the guest. + + +Run +=== + +0) Build trace agent in a guest + $ make + +1) Enable ftrace in the guest + + # echo 1 > /sys/kernel/tracing/events/sched/enable + +2) Run trace agent in the guest + This agent must be operated as root. + # ./trace-agent +read/write threads in the agent wait for start order from host. If you add -o +option, trace data are output via stdout in the guest. + +3) Open FIFO in a host + # cat /tmp/virtio-trace/trace-path-cpu0.out +If a host does not open these, trace data get stuck in buffers of virtio. Then, +the guest will stop by specification of chardev in QEMU. This blocking mode may +be solved in the future. + +4) Start to read trace data by ordering from a host + A host injects read start order to the guest via virtio-serial. + # echo 1 > /tmp/virtio-trace/agent-ctl-path.in + +5) Stop to read trace data by ordering from a host + A host injects read stop order to the guest via virtio-serial. + # echo 0 > /tmp/virtio-trace/agent-ctl-path.in -- cgit v1.3.1