rte_vhost requires all queues to be fully initialized
in order to start I/O processing. This behavior is not
compliant with the vhost-user specification and doesn't
work with QEMU 2.12+, which will only initialize 1 I/O
queue for the SeaBIOS boot. Theoretically, we should
start polling each virtqueue individually after
receiving its SET_VRING_KICK message, but rte_vhost is
not designed to poll individual queues. So we use
a workaround to detect when a vhost session could be
potentially at that SeaBIOS stage and we mark it to
start polling as soon as its first virtqueue gets
initialized. This doesn't hurt any non-QEMU vhost slaves
and allows QEMU 2.12+ to boot correctly. SET_FEATURES
could be sent at any time, but QEMU will send it at
least once on SeaBIOS initialization - whenever
powered-up or rebooted.
Vhost sessions are still mostly started/stopped from
within rte_vhost callbacks, but now there's additional
concept of "forced" polling, in which SPDK starts
sessions manually, while rte_vhost still thinks the
sessions are stopped. This can potentially lead to cases
where a session is "started" twice, or gets destroyed
while it's still being polled (by force). Those cases
also need to be handled within this patch.
Change-Id: I70636d63e27914906ddece59cec34f1dd37ec5cd
Signed-off-by: Darek Stojaczyk <dariusz.stojaczyk@intel.com>
Reviewed-on: https://review.gerrithub.io/c/spdk/spdk/+/446086
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Reviewed-by: Changpeng Liu <changpeng.liu@intel.com>
Reviewed-by: Jim Harris <james.r.harris@intel.com>
1ecbb6a8da