Mmiotrace raw log format

The binary log format

Some very old versions of MmioTrace dumped some version of a binary log format. You should forget about those, but if you can't, see if mmio-convert works for you. The binary format had several shortcomings.

The ascii log format

The modern raw MmioTrace log is text and easily filtered with e.g. grep and awk. One record is one line in the log. A record starts with a keyword, followed by keyword dependant arguments. Arguments are separated by a space, or continue until the end of line. This is how the log format looks like:

explanation	keyword	space separated arguments
read event	R	width (bytes)	timestamp	map id	address	value	PC	PID
write event	W	width (bytes)	timestamp	map id	address	value	PC	PID
ioremap event	MAP	timestamp	map id	physical	virtual	length	PC	PID
iounmap event	UNMAP	timestamp	map id	PC	PID
marker	MARK	timestamp	text
version	VERSION	string
info for reader	LSPCI	one line from `lspci -v`
PCI address map	PCIDEV	space separated /proc/bus/pci/devices data
unk. opcode	UNKNOWN	timestamp	map id	address	data	PC	PID

Timestamp is in seconds. Address and physical are physical addresses, virtual is a kernel virtual address. Map id is an arbitrary id number identifying the mapping that was used in an operation. PC is the program counter and PID is process id. PID is always zero as tracing user space memory events is not supported yet.

For instance, the following awk filter will pass all 32-bit writes that target physical addresses in the range [0xfb73ce40, 0xfb800000[

awk '/W 4 / { adr=strtonum($5); if (adr >= 0xfb73ce40 && adr < 0xfb800000) print; }'

Note, that to be able to use mmio-parse on the filtered output you need to re-add or preserve all MAP and PCIDEV records. You can do that easily by first filtering those into a separate file and then just running cat maps.txt awk-filtered.txt | mmio-parse... You can also use timestamps as unique (well, unique in practise) identifiers for events, when examining multiple filtrations of a log.

For filtering you are likely interested in register offsets and not physical addresses. Lspci lists PCI memory resources in physical addresses. For Nvidia, the first resource, a.k.a BAR 0, is the MMIO register range. It is marked as non-prefetchable. Register offsets are relative to BAR 0.