Commit 345f42b4 authored by Paul Durrant's avatar Paul Durrant Committed by Anthony PERARD
Browse files

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: default avatarPaul Durrant <paul.durrant@citrix.com>
Reviewed-by: default avatarAnthony PERARD <anthony.perard@citrix.com>
Message-Id: <20190408151617.13025-4-paul.durrant@citrix.com>
Signed-off-by: default avatarAnthony PERARD <anthony.perard@citrix.com>
parent 83361a8a

hw/block/dataplane/xen-block.c

+9 −8
Original line number Diff line number Diff line
@@ -318,7 +318,9 @@ static void xen_block_complete_aio(void *opaque, int ret) 
    }

    xen_block_release_request(request);



    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,

hw/xen/xen-bus.c

+9 −2
Original line number Diff line number Diff line
@@ -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);

include/hw/xen/xen-bus.h

+1 −1
Original line number Diff line number Diff line
@@ -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,