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[Qemu-block] [PATCH 3/3] xen-bus / xen-block: add support for event chan
From: |
Paul Durrant |
Subject: |
[Qemu-block] [PATCH 3/3] xen-bus / xen-block: add support for event channel polling |
Date: |
Mon, 8 Apr 2019 16:16:17 +0100 |
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 <address@hidden>
---
Cc: Stefan Hajnoczi <address@hidden>
Cc: Stefano Stabellini <address@hidden>
Cc: Anthony Perard <address@hidden>
Cc: Kevin Wolf <address@hidden>
Cc: Max Reitz <address@hidden>
---
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 1046f965c4..908bd27bbd 100644
--- a/hw/block/dataplane/xen-block.c
+++ b/hw/block/dataplane/xen-block.c
@@ -317,7 +317,9 @@ 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);
@@ -514,12 +516,13 @@ 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;
@@ -551,6 +554,7 @@ 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) {
@@ -602,10 +606,7 @@ 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)
@@ -617,11 +618,11 @@ 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 4f634d1291..c90fc62a8d 100644
--- a/hw/xen/xen-bus.c
+++ b/hw/xen/xen-bus.c
@@ -931,13 +931,20 @@ 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);
}
@@ -972,7 +979,7 @@ XenEventChannel *xen_device_bind_event_channel(XenDevice
*xendev,
channel->ctx = ctx;
aio_set_fd_handler(channel->ctx, xenevtchn_fd(channel->xeh), false,
- 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,
--
2.20.1.2.gb21ebb6
[Qemu-block] [PATCH 3/3] xen-bus / xen-block: add support for event channel polling,
Paul Durrant <=