Alexander Graf bae107c3fc Make char muxer more robust wrt small FIFOs ...

Virtio-Console can only process one character at a time. Using it on S390
gave me strange "lags" where I got the character I pressed before when
pressing one. So I typed in "abc" and only received "a", then pressed "d"
but the guest received "b" and so on.

While the stdio driver calls a poll function that just processes on its
queue in case virtio-console can't take multiple characters at once, the
muxer does not have such callbacks, so it can't empty its queue.

To work around that limitation, I introduced a new timer that only gets
active when the guest can not receive any more characters. In that case
it polls again after a while to check if the guest is now receiving input.

This patch fixes input when using -nographic on s390 for me.

[AF: Rebased for v2.7.0-rc2]
[BR: minor edits to pass qemu's checkpatch script]
Signed-off-by: Bruce Rogers <brogers@suse.com>

2023-12-06 10:44:55 +01:00

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