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xen-bus / xen-block: add support for event channel polling

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This patch introduces a poll callback for event channel fd-s and uses
this to invoke the channel callback function.

To properly support polling, it is necessary for the event channel callback
function to return a boolean saying whether it has done any useful work or
not. Thus xen_block_dataplane_event() is modified to directly invoke
xen_block_handle_requests() and the latter only returns true if it actually
processes any requests. This also means that the call to qemu_bh_schedule()
is moved into xen_block_complete_aio(), which is more intuitive since the
only reason for doing a deferred poll of the shared ring should be because
there were previously insufficient resources to fully complete a previous
poll.

Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
Reviewed-by: Anthony PERARD <anthony.perard@citrix.com>
Message-Id: <20190408151617.13025-4-paul.durrant@citrix.com>
Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
This commit is contained in:
Paul Durrant 2019-04-08 16:16:17 +01:00 • committed by Anthony PERARD
parent 83361a8a1f
commit 345f42b4be
3 changed files with 19 additions and 11 deletions
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11
hw/xen/xen-bus.c
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@ -932,13 +932,20 @@ struct XenEventChannel {
void *opaque;
};
static bool xen_device_poll(void *opaque)
{
XenEventChannel *channel = opaque;
return channel->handler(channel->opaque);
}
static void xen_device_event(void *opaque)
{
XenEventChannel *channel = opaque;
unsigned long port = xenevtchn_pending(channel->xeh);
if (port == channel->local_port) {
channel->handler(channel->opaque);
xen_device_poll(channel);
xenevtchn_unmask(channel->xeh, port);
}
@ -973,7 +980,7 @@ XenEventChannel *xen_device_bind_event_channel(XenDevice *xendev,
channel->ctx = ctx;
aio_set_fd_handler(channel->ctx, xenevtchn_fd(channel->xeh), true,
xen_device_event, NULL, NULL, channel);
xen_device_event, NULL, xen_device_poll, channel);
QLIST_INSERT_HEAD(&xendev->event_channels, channel, list);