From 345f42b4be9f9975ff3f7f3e95acae4f67c74f89 Mon Sep 17 00:00:00 2001 From: Paul Durrant Date: Mon, 8 Apr 2019 16:16:17 +0100 Subject: [PATCH] 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 Reviewed-by: Anthony PERARD Message-Id: <20190408151617.13025-4-paul.durrant@citrix.com> Signed-off-by: Anthony PERARD --- hw/block/dataplane/xen-block.c | 17 +++++++++-------- hw/xen/xen-bus.c | 11 +++++++++-- include/hw/xen/xen-bus.h | 2 +- 3 files changed, 19 insertions(+), 11 deletions(-) diff --git a/hw/block/dataplane/xen-block.c b/hw/block/dataplane/xen-block.c index aadca75644..0f200c5fb0 100644 --- a/hw/block/dataplane/xen-block.c +++ b/hw/block/dataplane/xen-block.c @@ -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, diff --git a/hw/xen/xen-bus.c b/hw/xen/xen-bus.c index 2210526490..7503eea9e9 100644 --- a/hw/xen/xen-bus.c +++ b/hw/xen/xen-bus.c @@ -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); diff --git a/include/hw/xen/xen-bus.h b/include/hw/xen/xen-bus.h index 8183b98c7d..1c2d9dfdb8 100644 --- a/include/hw/xen/xen-bus.h +++ b/include/hw/xen/xen-bus.h @@ -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, -- 2.11.0