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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>
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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17
hw/block/dataplane/xen-block.c
View File

@ -318,7 +318,9 @@ static void xen_block_complete_aio(void *opaque, int ret)
}
xen_block_release_request(request);
qemu_bh_schedule(dataplane->bh);
if (dataplane->more_work) {
qemu_bh_schedule(dataplane->bh);
}
done:
aio_context_release(dataplane->ctx);
@ -515,12 +517,13 @@ static int xen_block_get_request(XenBlockDataPlane *dataplane,
*/
#define IO_PLUG_THRESHOLD 1
static void xen_block_handle_requests(XenBlockDataPlane *dataplane)
static bool xen_block_handle_requests(XenBlockDataPlane *dataplane)
{
RING_IDX rc, rp;
XenBlockRequest *request;
int inflight_atstart = dataplane->requests_inflight;
int batched = 0;
bool done_something = false;
dataplane->more_work = 0;
@ -552,6 +555,7 @@ static void xen_block_handle_requests(XenBlockDataPlane *dataplane)
}
xen_block_get_request(dataplane, request, rc);
dataplane->rings.common.req_cons = ++rc;
done_something = true;
/* parse them */
if (xen_block_parse_request(request) != 0) {
@ -603,10 +607,7 @@ static void xen_block_handle_requests(XenBlockDataPlane *dataplane)
blk_io_unplug(dataplane->blk);
}
if (dataplane->more_work &&
dataplane->requests_inflight < dataplane->max_requests) {
qemu_bh_schedule(dataplane->bh);
}
return done_something;
}
static void xen_block_dataplane_bh(void *opaque)
@ -618,11 +619,11 @@ static void xen_block_dataplane_bh(void *opaque)
aio_context_release(dataplane->ctx);
}
static void xen_block_dataplane_event(void *opaque)
static bool xen_block_dataplane_event(void *opaque)
{
XenBlockDataPlane *dataplane = opaque;
qemu_bh_schedule(dataplane->bh);
return xen_block_handle_requests(dataplane);
}
XenBlockDataPlane *xen_block_dataplane_create(XenDevice *xendev,

11
hw/xen/xen-bus.c
View File

@ -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);

2
include/hw/xen/xen-bus.h
View File

@ -119,7 +119,7 @@ void xen_device_copy_grant_refs(XenDevice *xendev, bool to_domain,
XenDeviceGrantCopySegment segs[],
unsigned int nr_segs, Error **errp);
typedef void (*XenEventHandler)(void *opaque);
typedef bool (*XenEventHandler)(void *opaque);
XenEventChannel *xen_device_bind_event_channel(XenDevice *xendev,
AioContext *ctx,