mirror of https://github.com/xemu-project/xemu.git
xen-bus / xen-block: add support for event channel polling
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>
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@ -318,7 +318,9 @@ static void xen_block_complete_aio(void *opaque, int ret)
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}
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xen_block_release_request(request);
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qemu_bh_schedule(dataplane->bh);
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if (dataplane->more_work) {
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qemu_bh_schedule(dataplane->bh);
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}
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done:
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aio_context_release(dataplane->ctx);
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@ -515,12 +517,13 @@ static int xen_block_get_request(XenBlockDataPlane *dataplane,
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*/
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#define IO_PLUG_THRESHOLD 1
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static void xen_block_handle_requests(XenBlockDataPlane *dataplane)
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static bool xen_block_handle_requests(XenBlockDataPlane *dataplane)
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{
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RING_IDX rc, rp;
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XenBlockRequest *request;
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int inflight_atstart = dataplane->requests_inflight;
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int batched = 0;
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bool done_something = false;
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dataplane->more_work = 0;
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@ -552,6 +555,7 @@ static void xen_block_handle_requests(XenBlockDataPlane *dataplane)
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}
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xen_block_get_request(dataplane, request, rc);
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dataplane->rings.common.req_cons = ++rc;
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done_something = true;
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/* parse them */
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if (xen_block_parse_request(request) != 0) {
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@ -603,10 +607,7 @@ static void xen_block_handle_requests(XenBlockDataPlane *dataplane)
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blk_io_unplug(dataplane->blk);
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}
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if (dataplane->more_work &&
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dataplane->requests_inflight < dataplane->max_requests) {
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qemu_bh_schedule(dataplane->bh);
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}
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return done_something;
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}
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static void xen_block_dataplane_bh(void *opaque)
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@ -618,11 +619,11 @@ static void xen_block_dataplane_bh(void *opaque)
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aio_context_release(dataplane->ctx);
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}
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static void xen_block_dataplane_event(void *opaque)
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static bool xen_block_dataplane_event(void *opaque)
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{
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XenBlockDataPlane *dataplane = opaque;
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qemu_bh_schedule(dataplane->bh);
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return xen_block_handle_requests(dataplane);
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}
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XenBlockDataPlane *xen_block_dataplane_create(XenDevice *xendev,
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@ -932,13 +932,20 @@ struct XenEventChannel {
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void *opaque;
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};
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static bool xen_device_poll(void *opaque)
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{
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XenEventChannel *channel = opaque;
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return channel->handler(channel->opaque);
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}
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static void xen_device_event(void *opaque)
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{
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XenEventChannel *channel = opaque;
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unsigned long port = xenevtchn_pending(channel->xeh);
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if (port == channel->local_port) {
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channel->handler(channel->opaque);
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xen_device_poll(channel);
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xenevtchn_unmask(channel->xeh, port);
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}
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@ -973,7 +980,7 @@ XenEventChannel *xen_device_bind_event_channel(XenDevice *xendev,
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channel->ctx = ctx;
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aio_set_fd_handler(channel->ctx, xenevtchn_fd(channel->xeh), true,
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xen_device_event, NULL, NULL, channel);
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xen_device_event, NULL, xen_device_poll, channel);
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QLIST_INSERT_HEAD(&xendev->event_channels, channel, list);
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@ -119,7 +119,7 @@ void xen_device_copy_grant_refs(XenDevice *xendev, bool to_domain,
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XenDeviceGrantCopySegment segs[],
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unsigned int nr_segs, Error **errp);
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typedef void (*XenEventHandler)(void *opaque);
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typedef bool (*XenEventHandler)(void *opaque);
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XenEventChannel *xen_device_bind_event_channel(XenDevice *xendev,
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AioContext *ctx,
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