[kvm-unit-tests PATCH 1/7] arch-run: Keep infifo open

Nicholas Piggin
2024-02-26T09:38:53Z

The infifo fifo that is used to send characters to QEMU console is
only able to receive one character before the cat process exits.
Supporting interactions between test and harness involving multiple
characters requires the fifo to remain open.

This also allows us to let the cat out of the bag, simplifying the
input pipeline.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
scripts/arch-run.bash | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/scripts/arch-run.bash b/scripts/arch-run.bash
index 6daef3218..e5b36a07b 100644
--- a/scripts/arch-run.bash
+++ b/scripts/arch-run.bash
@@ -158,6 +158,11 @@ run_migration ()
mkfifo ${src_outfifo}
mkfifo ${dst_outfifo}

+ # Holding both ends of the input fifo open prevents opens from
+ # blocking and readers getting EOF when a writer closes it.
+ mkfifo ${dst_infifo}
+ exec {dst_infifo_fd}<>${dst_infifo}
+
eval "$migcmdline" \
-chardev socket,id=mon,path=${src_qmp},server=on,wait=off \
-mon chardev=mon,mode=control > ${src_outfifo} &
@@ -191,14 +196,10 @@ run_migration ()

do_migration ()
{
- # We have to use cat to open the named FIFO, because named FIFO's,
- # unlike pipes, will block on open() until the other end is also
- # opened, and that totally breaks QEMU...
- mkfifo ${dst_infifo}
eval "$migcmdline" \
-chardev socket,id=mon,path=${dst_qmp},server=on,wait=off \
-mon chardev=mon,mode=control -incoming unix:${dst_incoming} \
- < <(cat ${dst_infifo}) > ${dst_outfifo} &
+ < ${dst_infifo} > ${dst_outfifo} &
incoming_pid=$!
cat ${dst_outfifo} | tee ${dst_out} | filter_quiet_msgs &

@@ -245,7 +246,6 @@ do_migration ()

# keypress to dst so getchar completes and test continues
echo > ${dst_infifo}
- rm ${dst_infifo}

# Ensure the incoming socket is removed, ready for next destination
if [ -S ${dst_incoming} ] ; then
--
2.42.0