66 lines
2.8 KiB
Diff
66 lines
2.8 KiB
Diff
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Hanna Czenczek <hreitz@redhat.com>
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Date: Fri, 2 Feb 2024 16:31:56 +0100
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Subject: [PATCH] virtio-scsi: Attach event vq notifier with no_poll
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As of commit 38738f7dbbda90fbc161757b7f4be35b52205552 ("virtio-scsi:
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don't waste CPU polling the event virtqueue"), we only attach an io_read
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notifier for the virtio-scsi event virtqueue instead, and no polling
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notifiers. During operation, the event virtqueue is typically
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non-empty, but none of the buffers are intended to be used immediately.
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Instead, they only get used when certain events occur. Therefore, it
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makes no sense to continuously poll it when non-empty, because it is
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supposed to be and stay non-empty.
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We do this by using virtio_queue_aio_attach_host_notifier_no_poll()
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instead of virtio_queue_aio_attach_host_notifier() for the event
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virtqueue.
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Commit 766aa2de0f29b657148e04599320d771c36fd126 ("virtio-scsi: implement
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BlockDevOps->drained_begin()") however has virtio_scsi_drained_end() use
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virtio_queue_aio_attach_host_notifier() for all virtqueues, including
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the event virtqueue. This can lead to it being polled again, undoing
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the benefit of commit 38738f7dbbda90fbc161757b7f4be35b52205552.
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Fix it by using virtio_queue_aio_attach_host_notifier_no_poll() for the
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event virtqueue.
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("virtio-scsi: implement BlockDevOps->drained_begin()")
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Reported-by: Fiona Ebner <f.ebner@proxmox.com>
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Fixes: 766aa2de0f29b657148e04599320d771c36fd126
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Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
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Tested-by: Fiona Ebner <f.ebner@proxmox.com>
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Reviewed-by: Fiona Ebner <f.ebner@proxmox.com>
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Signed-off-by: Hanna Czenczek <hreitz@redhat.com>
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Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
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---
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hw/scsi/virtio-scsi.c | 7 ++++++-
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1 file changed, 6 insertions(+), 1 deletion(-)
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diff --git a/hw/scsi/virtio-scsi.c b/hw/scsi/virtio-scsi.c
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index 45b95ea070..ad24a882fd 100644
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--- a/hw/scsi/virtio-scsi.c
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+++ b/hw/scsi/virtio-scsi.c
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@@ -1148,6 +1148,7 @@ static void virtio_scsi_drained_begin(SCSIBus *bus)
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static void virtio_scsi_drained_end(SCSIBus *bus)
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{
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VirtIOSCSI *s = container_of(bus, VirtIOSCSI, bus);
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+ VirtIOSCSICommon *vs = VIRTIO_SCSI_COMMON(s);
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VirtIODevice *vdev = VIRTIO_DEVICE(s);
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uint32_t total_queues = VIRTIO_SCSI_VQ_NUM_FIXED +
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s->parent_obj.conf.num_queues;
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@@ -1165,7 +1166,11 @@ static void virtio_scsi_drained_end(SCSIBus *bus)
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for (uint32_t i = 0; i < total_queues; i++) {
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VirtQueue *vq = virtio_get_queue(vdev, i);
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- virtio_queue_aio_attach_host_notifier(vq, s->ctx);
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+ if (vq == vs->event_vq) {
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+ virtio_queue_aio_attach_host_notifier_no_poll(vq, s->ctx);
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+ } else {
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+ virtio_queue_aio_attach_host_notifier(vq, s->ctx);
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+ }
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}
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}
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