The current implementation of the 'kvm_pio' tracepoint in emulator_pio_in_out()
only tells us that 'something' has been read from or written to an I/O port. To
improve the usability of the tracepoint, I propose to include the value/content
that has been read or written in the trace output. The proposed patch aims at
the more common case where a single 8-bit or 16-bit or 32-bit value has been
read or written -- it does not fully cover the case where 'count' is greater
than one.
This is an example of what the patch can do (trace of PCI config space access).
- on the host
# trace-cmd record -e kvm:kvm_pio -f "(port >= 0xcf8) && (port <= 0xcff)"
/sys/kernel/debug/tracing/events/kvm/kvm_pio/filter
Hit Ctrl^C to stop recording
- in a Linux guest
# dd if=/sys/bus/pci/devices/0000:00:06.0/config bs=2 count=4 | hexdump
4+0 records in
4+0 records out
8 bytes (8 B) copied, 0.000114056 s, 70.1 kB/s
0000000 1af4 1001 0507 0010
0000008
- on the host
# trace-cmd report
...
qemu-kvm-23216 [001] 15211.994089: kvm_pio: pio_write
at 0xcf8 size 4 count 1 val 0x80003000
qemu-kvm-23216 [001] 15211.994108: kvm_pio: pio_read
at 0xcfc size 2 count 1 val 0x1af4
qemu-kvm-23216 [001] 15211.994129: kvm_pio: pio_write
at 0xcf8 size 4 count 1 val 0x80003000
qemu-kvm-23216 [001] 15211.994136: kvm_pio: pio_read
at 0xcfe size 2 count 1 val 0x1001
qemu-kvm-23216 [001] 15211.994143: kvm_pio: pio_write
at 0xcf8 size 4 count 1 val 0x80003004
qemu-kvm-23216 [001] 15211.994150: kvm_pio: pio_read
at 0xcfc size 2 count 1 val 0x507
qemu-kvm-23216 [001] 15211.994155: kvm_pio: pio_write
at 0xcf8 size 4 count 1 val 0x80003004
qemu-kvm-23216 [001] 15211.994161: kvm_pio: pio_read
at 0xcfe size 2 count 1 val 0x10
Ulrich Obergfell (1):
improve the usability of the 'kvm_pio' tracepoint
arch/x86/kvm/trace.h | 20 ++++++++++++++++----
arch/x86/kvm/x86.c | 4 ++--
2 files changed, 18 insertions(+), 6 deletions(-)
--
1.7.11.7
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