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From 5aaf33dbbbc89d58a52337985641723b9ee13541 Mon Sep 17 00:00:00 2001
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From: Stefan Hajnoczi <stefanha@redhat.com>
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Date: Wed, 27 Apr 2022 15:35:36 +0100
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Subject: [PATCH 09/16] virtio-scsi: fix ctrl and event handler functions in
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dataplane mode
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RH-Author: Stefan Hajnoczi <stefanha@redhat.com>
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RH-MergeRequest: 88: virtio-scsi: fix 100% CPU consumption with IOThreads
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RH-Commit: [1/6] 3087889041b960f14a6b3893243f78523a78f637 (stefanha/centos-stream-qemu-kvm)
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RH-Bugzilla: 2079347
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RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>
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RH-Acked-by: Kevin Wolf <kwolf@redhat.com>
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RH-Acked-by: Stefano Garzarella <sgarzare@redhat.com>
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Commit f34e8d8b8d48d73f36a67b6d5e492ef9784b5012 ("virtio-scsi: prepare
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virtio_scsi_handle_cmd for dataplane") prepared the virtio-scsi cmd
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virtqueue handler function to be used in both the dataplane and
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non-datpalane code paths.
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It failed to convert the ctrl and event virtqueue handler functions,
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which are not designed to be called from the dataplane code path but
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will be since the ioeventfd is set up for those virtqueues when
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dataplane starts.
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Convert the ctrl and event virtqueue handler functions now so they
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operate correctly when called from the dataplane code path. Avoid code
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duplication by extracting this code into a helper function.
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Fixes: f34e8d8b8d48d73f36a67b6d5e492ef9784b5012 ("virtio-scsi: prepare virtio_scsi_handle_cmd for dataplane")
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
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Message-id: 20220427143541.119567-2-stefanha@redhat.com
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[Fixed s/by used/be used/ typo pointed out by Michael Tokarev
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<mjt@tls.msk.ru>.
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--Stefan]
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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(cherry picked from commit 2f743ef6366c2df4ef51ef3ae318138cdc0125ab)
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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---
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hw/scsi/virtio-scsi.c | 42 +++++++++++++++++++++++++++---------------
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1 file changed, 27 insertions(+), 15 deletions(-)
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diff --git a/hw/scsi/virtio-scsi.c b/hw/scsi/virtio-scsi.c
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index 7f6da33a8a..7b69eeed64 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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@@ -472,16 +472,32 @@ bool virtio_scsi_handle_ctrl_vq(VirtIOSCSI *s, VirtQueue *vq)
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return progress;
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}
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+/*
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+ * If dataplane is configured but not yet started, do so now and return true on
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+ * success.
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+ *
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+ * Dataplane is started by the core virtio code but virtqueue handler functions
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+ * can also be invoked when a guest kicks before DRIVER_OK, so this helper
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+ * function helps us deal with manually starting ioeventfd in that case.
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+ */
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+static bool virtio_scsi_defer_to_dataplane(VirtIOSCSI *s)
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+{
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+ if (!s->ctx || s->dataplane_started) {
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+ return false;
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+ }
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+
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+ virtio_device_start_ioeventfd(&s->parent_obj.parent_obj);
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+ return !s->dataplane_fenced;
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+}
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+
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static void virtio_scsi_handle_ctrl(VirtIODevice *vdev, VirtQueue *vq)
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{
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VirtIOSCSI *s = (VirtIOSCSI *)vdev;
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- if (s->ctx) {
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- virtio_device_start_ioeventfd(vdev);
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- if (!s->dataplane_fenced) {
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- return;
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- }
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+ if (virtio_scsi_defer_to_dataplane(s)) {
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+ return;
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}
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+
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virtio_scsi_acquire(s);
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virtio_scsi_handle_ctrl_vq(s, vq);
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virtio_scsi_release(s);
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@@ -720,12 +736,10 @@ static void virtio_scsi_handle_cmd(VirtIODevice *vdev, VirtQueue *vq)
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/* use non-QOM casts in the data path */
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VirtIOSCSI *s = (VirtIOSCSI *)vdev;
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- if (s->ctx && !s->dataplane_started) {
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- virtio_device_start_ioeventfd(vdev);
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- if (!s->dataplane_fenced) {
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- return;
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- }
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+ if (virtio_scsi_defer_to_dataplane(s)) {
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+ return;
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}
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+
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virtio_scsi_acquire(s);
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virtio_scsi_handle_cmd_vq(s, vq);
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virtio_scsi_release(s);
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@@ -855,12 +869,10 @@ static void virtio_scsi_handle_event(VirtIODevice *vdev, VirtQueue *vq)
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{
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VirtIOSCSI *s = VIRTIO_SCSI(vdev);
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- if (s->ctx) {
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- virtio_device_start_ioeventfd(vdev);
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- if (!s->dataplane_fenced) {
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- return;
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- }
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+ if (virtio_scsi_defer_to_dataplane(s)) {
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+ return;
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}
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+
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virtio_scsi_acquire(s);
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virtio_scsi_handle_event_vq(s, vq);
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virtio_scsi_release(s);
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--
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2.31.1
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