Re: [kvm-unit-tests PATCH v3 4/8] migration: Support multiple migrations

Thomas Huth
2024-02-09T08:44:24Z

On 09/02/2024 09.39, Nicholas Piggin wrote:
> On Fri Feb 9, 2024 at 6:19 PM AEST, Thomas Huth wrote:
>> On 09/02/2024 08.01, Nicholas Piggin wrote:
>>> Support multiple migrations by flipping dest file/socket variables to
>>> source after the migration is complete, ready to start again. A new
>>> destination is created if the test outputs the migrate line again.
>>> Test cases may now switch to calling migrate() one or more times.
>>>
>>> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
>>> ---
>> ...
>>> diff --git a/scripts/arch-run.bash b/scripts/arch-run.bash
>>> index 3689d7c2..a914ba17 100644
>>> --- a/scripts/arch-run.bash
>>> +++ b/scripts/arch-run.bash
>>> @@ -129,12 +129,16 @@ run_migration ()
>>> return 77
>>> fi
>>>
>>> + migcmdline=$@
>>> +
>>> trap 'trap - TERM ; kill 0 ; exit 2' INT TERM
>>> - trap 'rm -f ${migout1} ${migout_fifo1} ${migsock} ${qmp1} ${qmp2} ${fifo}' RETURN EXIT
>>> + trap 'rm -f ${migout1} ${migout2} ${migout_fifo1} ${migout_fifo2} ${migsock} ${qmp1} ${qmp2} ${fifo}' RETURN EXIT
>>>
>>> migsock=$(mktemp -u -t mig-helper-socket.XXXXXXXXXX)
>>> migout1=$(mktemp -t mig-helper-stdout1.XXXXXXXXXX)
>>> migout_fifo1=$(mktemp -u -t mig-helper-fifo-stdout1.XXXXXXXXXX)
>>> + migout2=$(mktemp -t mig-helper-stdout2.XXXXXXXXXX)
>>> + migout_fifo2=$(mktemp -u -t mig-helper-fifo-stdout2.XXXXXXXXXX)
>>> qmp1=$(mktemp -u -t mig-helper-qmp1.XXXXXXXXXX)
>>> qmp2=$(mktemp -u -t mig-helper-qmp2.XXXXXXXXXX)
>>> fifo=$(mktemp -u -t mig-helper-fifo.XXXXXXXXXX)
>>> @@ -142,18 +146,61 @@ run_migration ()
>>> qmpout2=/dev/null
>>>
>>> mkfifo ${migout_fifo1}
>>> - eval "$@" -chardev socket,id=mon1,path=${qmp1},server=on,wait=off \
>>> + mkfifo ${migout_fifo2}
>>> +
>>> + eval "$migcmdline" \
>>> + -chardev socket,id=mon1,path=${qmp1},server=on,wait=off \
>>> -mon chardev=mon1,mode=control > ${migout_fifo1} &
>>> live_pid=$!
>>> cat ${migout_fifo1} | tee ${migout1} &
>>>
>>> - # 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...
>>> + # The test must prompt the user to migrate, so wait for the "migrate"
>>> + # keyword
>>> + while ! grep -q -i "Now migrate the VM" < ${migout1} ; do
>>> + if ! ps -p ${live_pid} > /dev/null ; then
>>> + echo "ERROR: Test exit before migration point." >&2
>>> + qmp ${qmp1} '"quit"'> ${qmpout1} 2>/dev/null
>>> + return 3
>>> + fi
>>> + sleep 0.1
>>> + done
>>> +
>>> + # This starts the first source QEMU in advance of the test reaching the
>>> + # migration point, since we expect at least one migration. Subsequent
>>> + # sources are started as the test hits migrate keywords.
>>> + do_migration || return $?
>>> +
>>> + while ps -p ${live_pid} > /dev/null ; do
>>> + # Wait for EXIT or further migrations
>>> + if ! grep -q -i "Now migrate the VM" < ${migout1} ; then
>>> + sleep 0.1
>>> + else
>>> + do_migration || return $?
>>> + fi
>>> + done
>>> +
>>> + wait ${live_pid}
>>> + ret=$?
>>> +
>>> + while (( $(jobs -r | wc -l) > 0 )); do
>>> + sleep 0.1
>>> + done
>>> +
>>> + return $ret
>>> +}
>>> +
>>> +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 ${fifo}
>>> - eval "$@" -chardev socket,id=mon2,path=${qmp2},server=on,wait=off \
>>> - -mon chardev=mon2,mode=control -incoming unix:${migsock} < <(cat ${fifo}) &
>>> + eval "$migcmdline" \
>>> + -chardev socket,id=mon2,path=${qmp2},server=on,wait=off \
>>> + -mon chardev=mon2,mode=control -incoming unix:${migsock} \
>>> + < <(cat ${fifo}) > ${migout_fifo2} &
>>> incoming_pid=$!
>>> + cat ${migout_fifo2} | tee ${migout2} &
>>>
>>> # The test must prompt the user to migrate, so wait for the "migrate" keyword
>>> while ! grep -q -i "Now migrate the VM" < ${migout1} ; do
>>
>> So the old check for the "migrate" keyword is also still around?
>
> It's just the comment is staleish, it only checks "Now migrate...".
>
>> Why do we
>> need to wait on two spots for the "Now mirgrate..." string now?
>
> So that the it ensures we do one migration, subsequent ones are
> optional.
>
> I was thinking we could just remove that, and possibly even
> remove the MIGRATION=yes/no paths and always just use the same
> code here. But that's for another time.
>
> Actually there is some weirdness here. There are *three* spots
> where it waits for migration.

Yes, that's what I meant (I considered your two new additions like one spot ;-))

> The first one in run_migration
> can be removed, because it can call do_migration right away
> to start up the destination qemu process ahead of the first
> migration message as-per comment. I'll respin with that change.

Thanks, that sounds good!

Thomas