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73 lines
2.6 KiB
73 lines
2.6 KiB
8 months ago
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From f62b56c68d50a149a07e15797bf3605e63b2c501 Mon Sep 17 00:00:00 2001
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From: Stefan Hajnoczi <stefanha@redhat.com>
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Date: Mon, 22 Jan 2024 12:26:25 -0500
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Subject: [PATCH 4/6] virtio-blk: avoid using ioeventfd state in irqfd
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conditional
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RH-Author: Stefan Hajnoczi <stefanha@redhat.com>
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RH-MergeRequest: 224: virtio-blk: avoid using ioeventfd state in irqfd conditional
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RH-Jira: RHEL-15394
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RH-Acked-by: Kevin Wolf <kwolf@redhat.com>
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RH-Acked-by: Hanna Czenczek <hreitz@redhat.com>
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RH-Commit: [1/1] 8f24084669db52457e55e2523b9f56f5560dd6ce (stefanha/centos-stream-qemu-kvm)
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Requests that complete in an IOThread use irqfd to notify the guest
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while requests that complete in the main loop thread use the traditional
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qdev irq code path. The reason for this conditional is that the irq code
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path requires the BQL:
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if (s->ioeventfd_started && !s->ioeventfd_disabled) {
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virtio_notify_irqfd(vdev, req->vq);
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} else {
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virtio_notify(vdev, req->vq);
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}
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There is a corner case where the conditional invokes the irq code path
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instead of the irqfd code path:
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static void virtio_blk_stop_ioeventfd(VirtIODevice *vdev)
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{
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...
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/*
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* Set ->ioeventfd_started to false before draining so that host notifiers
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* are not detached/attached anymore.
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*/
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s->ioeventfd_started = false;
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/* Wait for virtio_blk_dma_restart_bh() and in flight I/O to complete */
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blk_drain(s->conf.conf.blk);
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During blk_drain() the conditional produces the wrong result because
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ioeventfd_started is false.
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Use qemu_in_iothread() instead of checking the ioeventfd state.
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Cc: qemu-stable@nongnu.org
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Buglink: https://issues.redhat.com/browse/RHEL-15394
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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Message-ID: <20240122172625.415386-1-stefanha@redhat.com>
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Reviewed-by: Kevin Wolf <kwolf@redhat.com>
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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(cherry picked from commit bfa36802d1704fc413c590ebdcc4e5ae0eacf439)
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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---
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hw/block/virtio-blk.c | 2 +-
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1 file changed, 1 insertion(+), 1 deletion(-)
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diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
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index 7fdeaf2d12..2ae2f6a823 100644
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--- a/hw/block/virtio-blk.c
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+++ b/hw/block/virtio-blk.c
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@@ -66,7 +66,7 @@ static void virtio_blk_req_complete(VirtIOBlockReq *req, unsigned char status)
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iov_discard_undo(&req->inhdr_undo);
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iov_discard_undo(&req->outhdr_undo);
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virtqueue_push(req->vq, &req->elem, req->in_len);
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- if (s->ioeventfd_started && !s->ioeventfd_disabled) {
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+ if (qemu_in_iothread()) {
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virtio_notify_irqfd(vdev, req->vq);
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} else {
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virtio_notify(vdev, req->vq);
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--
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2.39.3
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