From 83d768b5640946b7da55ce8335509df297e2c7cd Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Fri, 18 Nov 2016 16:07:02 +0100 Subject: virtio: set ISR on dataplane notifications Dataplane has been omitting forever the step of setting ISR when an interrupt is raised. This caused little breakage, because the specification actually says that ISR may not be updated in MSI mode. Some versions of the Windows drivers however didn't clear MSI mode correctly, and proceeded using polling mode (using ISR, not the used ring index!) for crashdump and hibernation. If it were just crashdump and hibernation it would not be a big deal, but recent releases of Windows do not really shut down, but rather log out and hibernate to make the next startup faster. Hence, this manifested as a more serious hang during shutdown with e.g. Windows 8.1 and virtio-win 1.8.0 RPMs. Newer versions fixed this, while older versions do not use MSI at all. The failure has always been there for virtio dataplane, but it became visible after commits 9ffe337 ("virtio-blk: always use dataplane path if ioeventfd is active", 2016-10-30) and ad07cd6 ("virtio-scsi: always use dataplane path if ioeventfd is active", 2016-10-30) made virtio-blk and virtio-scsi always use the dataplane code under KVM. The good news therefore is that it was not a bug in the patches---they were doing exactly what they were meant for, i.e. shake out remaining dataplane bugs. The fix is not hard, so it's worth arranging for the broken drivers. The virtio_should_notify+event_notifier_set pair that is common to virtio-blk and virtio-scsi dataplane is replaced with a new public function virtio_notify_irqfd that also sets ISR. The irqfd emulation code now need not set ISR anymore, so virtio_irq is removed. Reviewed-by: Stefan Hajnoczi Tested-by: Farhan Ali Tested-by: Alex Williamson Signed-off-by: Paolo Bonzini Reviewed-by: Michael S. Tsirkin Signed-off-by: Michael S. Tsirkin --- hw/block/dataplane/virtio-blk.c | 4 +--- hw/scsi/virtio-scsi-dataplane.c | 7 ------- hw/scsi/virtio-scsi.c | 2 +- hw/virtio/trace-events | 2 +- hw/virtio/virtio.c | 36 ++++++++++++++++++++++++++++-------- 5 files changed, 31 insertions(+), 20 deletions(-) (limited to 'hw') diff --git a/hw/block/dataplane/virtio-blk.c b/hw/block/dataplane/virtio-blk.c index 90ef557..d1f9f63 100644 --- a/hw/block/dataplane/virtio-blk.c +++ b/hw/block/dataplane/virtio-blk.c @@ -68,9 +68,7 @@ static void notify_guest_bh(void *opaque) unsigned i = j + ctzl(bits); VirtQueue *vq = virtio_get_queue(s->vdev, i); - if (virtio_should_notify(s->vdev, vq)) { - event_notifier_set(virtio_queue_get_guest_notifier(vq)); - } + virtio_notify_irqfd(s->vdev, vq); bits &= bits - 1; /* clear right-most bit */ } diff --git a/hw/scsi/virtio-scsi-dataplane.c b/hw/scsi/virtio-scsi-dataplane.c index f2ea29d..6b8d0f0 100644 --- a/hw/scsi/virtio-scsi-dataplane.c +++ b/hw/scsi/virtio-scsi-dataplane.c @@ -95,13 +95,6 @@ static int virtio_scsi_vring_init(VirtIOSCSI *s, VirtQueue *vq, int n, return 0; } -void virtio_scsi_dataplane_notify(VirtIODevice *vdev, VirtIOSCSIReq *req) -{ - if (virtio_should_notify(vdev, req->vq)) { - event_notifier_set(virtio_queue_get_guest_notifier(req->vq)); - } -} - /* assumes s->ctx held */ static void virtio_scsi_clear_aio(VirtIOSCSI *s) { diff --git a/hw/scsi/virtio-scsi.c b/hw/scsi/virtio-scsi.c index 3e5ae6a..10fd687 100644 --- a/hw/scsi/virtio-scsi.c +++ b/hw/scsi/virtio-scsi.c @@ -69,7 +69,7 @@ static void virtio_scsi_complete_req(VirtIOSCSIReq *req) qemu_iovec_from_buf(&req->resp_iov, 0, &req->resp, req->resp_size); virtqueue_push(vq, &req->elem, req->qsgl.size + req->resp_iov.size); if (s->dataplane_started && !s->dataplane_fenced) { - virtio_scsi_dataplane_notify(vdev, req); + virtio_notify_irqfd(vdev, vq); } else { virtio_notify(vdev, vq); } diff --git a/hw/virtio/trace-events b/hw/virtio/trace-events index 8756cef..7b6f55e 100644 --- a/hw/virtio/trace-events +++ b/hw/virtio/trace-events @@ -5,7 +5,7 @@ virtqueue_fill(void *vq, const void *elem, unsigned int len, unsigned int idx) " virtqueue_flush(void *vq, unsigned int count) "vq %p count %u" virtqueue_pop(void *vq, void *elem, unsigned int in_num, unsigned int out_num) "vq %p elem %p in_num %u out_num %u" virtio_queue_notify(void *vdev, int n, void *vq) "vdev %p n %d vq %p" -virtio_irq(void *vq) "vq %p" +virtio_notify_irqfd(void *vdev, void *vq) "vdev %p vq %p" virtio_notify(void *vdev, void *vq) "vdev %p vq %p" virtio_set_status(void *vdev, uint8_t val) "vdev %p val %u" diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c index 138a414..1af2de2 100644 --- a/hw/virtio/virtio.c +++ b/hw/virtio/virtio.c @@ -1330,13 +1330,6 @@ static void virtio_set_isr(VirtIODevice *vdev, int value) } } -void virtio_irq(VirtQueue *vq) -{ - trace_virtio_irq(vq); - virtio_set_isr(vq->vdev, 0x1); - virtio_notify_vector(vq->vdev, vq->vector); -} - bool virtio_should_notify(VirtIODevice *vdev, VirtQueue *vq) { uint16_t old, new; @@ -1360,6 +1353,33 @@ bool virtio_should_notify(VirtIODevice *vdev, VirtQueue *vq) return !v || vring_need_event(vring_get_used_event(vq), new, old); } +void virtio_notify_irqfd(VirtIODevice *vdev, VirtQueue *vq) +{ + if (!virtio_should_notify(vdev, vq)) { + return; + } + + trace_virtio_notify_irqfd(vdev, vq); + + /* + * virtio spec 1.0 says ISR bit 0 should be ignored with MSI, but + * windows drivers included in virtio-win 1.8.0 (circa 2015) are + * incorrectly polling this bit during crashdump and hibernation + * in MSI mode, causing a hang if this bit is never updated. + * Recent releases of Windows do not really shut down, but rather + * log out and hibernate to make the next startup faster. Hence, + * this manifested as a more serious hang during shutdown with + * + * Next driver release from 2016 fixed this problem, so working around it + * is not a must, but it's easy to do so let's do it here. + * + * Note: it's safe to update ISR from any thread as it was switched + * to an atomic operation. + */ + virtio_set_isr(vq->vdev, 0x1); + event_notifier_set(&vq->guest_notifier); +} + void virtio_notify(VirtIODevice *vdev, VirtQueue *vq) { if (!virtio_should_notify(vdev, vq)) { @@ -1994,7 +2014,7 @@ static void virtio_queue_guest_notifier_read(EventNotifier *n) { VirtQueue *vq = container_of(n, VirtQueue, guest_notifier); if (event_notifier_test_and_clear(n)) { - virtio_irq(vq); + virtio_notify_vector(vq->vdev, vq->vector); } } -- cgit v1.1