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monitor_qmp_dispatcher_co() runs in the iohandler AioContext that is not polled during nested event loops. The coroutine currently reschedules itself in the main loop's qemu_aio_context AioContext, which is polled during nested event loops. One known problem is that QMP device-add calls drain_call_rcu(), which temporarily drops the BQL, leading to all sorts of havoc like other vCPU threads re-entering device emulation code while another vCPU thread is waiting in device emulation code with aio_poll(). Paolo Bonzini suggested running non-coroutine QMP handlers in the iohandler AioContext. This avoids trouble with nested event loops. His original idea was to move coroutine rescheduling to monitor_qmp_dispatch(), but I resorted to moving it to qmp_dispatch() because we don't know if the QMP handler needs to run in coroutine context in monitor_qmp_dispatch(). monitor_qmp_dispatch() would have been nicer since it's associated with the monitor implementation and not as general as qmp_dispatch(), which is also used by qemu-ga. A number of qemu-iotests need updated .out files because the order of QMP events vs QMP responses has changed. Solves Issue #1933. Cc: qemu-stable@nongnu.org Fixes:7bed89958b("device_core: use drain_call_rcu in in qmp_device_add") Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=2215192 Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=2214985 Buglink: https://issues.redhat.com/browse/RHEL-17369 Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Message-ID: <20240118144823.1497953-4-stefanha@redhat.com> Reviewed-by: Kevin Wolf <kwolf@redhat.com> Tested-by: Fiona Ebner <f.ebner@proxmox.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com> (cherry picked from commiteffd60c878) Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
=== This is the QEMU I/O test suite === * Intro This package contains a simple test suite for the I/O layer of qemu. It does not require a guest, but only the qemu, qemu-img and qemu-io binaries. This does limit it to exercise the low-level I/O path only but no actual block drivers like ide, scsi or virtio. * Usage Just run ./check to run all tests for the raw image format, or ./check -qcow2 to test the qcow2 image format. The output of ./check -h explains additional options to test further image formats or I/O methods. * Feedback and patches Please send improvements to the test suite, general feedback or just reports of failing tests cases to qemu-devel@nongnu.org with a CC: to qemu-block@nongnu.org.