From 5aaf33dbbbc89d58a52337985641723b9ee13541 Mon Sep 17 00:00:00 2001 From: Stefan Hajnoczi Date: Wed, 27 Apr 2022 15:35:36 +0100 Subject: [PATCH 09/16] virtio-scsi: fix ctrl and event handler functions in dataplane mode RH-Author: Stefan Hajnoczi RH-MergeRequest: 88: virtio-scsi: fix 100% CPU consumption with IOThreads RH-Commit: [1/6] 3087889041b960f14a6b3893243f78523a78f637 (stefanha/centos-stream-qemu-kvm) RH-Bugzilla: 2079347 RH-Acked-by: Miroslav Rezanina RH-Acked-by: Kevin Wolf RH-Acked-by: Stefano Garzarella Commit f34e8d8b8d48d73f36a67b6d5e492ef9784b5012 ("virtio-scsi: prepare virtio_scsi_handle_cmd for dataplane") prepared the virtio-scsi cmd virtqueue handler function to be used in both the dataplane and non-datpalane code paths. It failed to convert the ctrl and event virtqueue handler functions, which are not designed to be called from the dataplane code path but will be since the ioeventfd is set up for those virtqueues when dataplane starts. Convert the ctrl and event virtqueue handler functions now so they operate correctly when called from the dataplane code path. Avoid code duplication by extracting this code into a helper function. Fixes: f34e8d8b8d48d73f36a67b6d5e492ef9784b5012 ("virtio-scsi: prepare virtio_scsi_handle_cmd for dataplane") Signed-off-by: Stefan Hajnoczi Reviewed-by: Paolo Bonzini Message-id: 20220427143541.119567-2-stefanha@redhat.com [Fixed s/by used/be used/ typo pointed out by Michael Tokarev . --Stefan] Signed-off-by: Stefan Hajnoczi (cherry picked from commit 2f743ef6366c2df4ef51ef3ae318138cdc0125ab) Signed-off-by: Stefan Hajnoczi --- hw/scsi/virtio-scsi.c | 42 +++++++++++++++++++++++++++--------------- 1 file changed, 27 insertions(+), 15 deletions(-) diff --git a/hw/scsi/virtio-scsi.c b/hw/scsi/virtio-scsi.c index 7f6da33a8a..7b69eeed64 100644 --- a/hw/scsi/virtio-scsi.c +++ b/hw/scsi/virtio-scsi.c @@ -472,16 +472,32 @@ bool virtio_scsi_handle_ctrl_vq(VirtIOSCSI *s, VirtQueue *vq) return progress; } +/* + * If dataplane is configured but not yet started, do so now and return true on + * success. + * + * Dataplane is started by the core virtio code but virtqueue handler functions + * can also be invoked when a guest kicks before DRIVER_OK, so this helper + * function helps us deal with manually starting ioeventfd in that case. + */ +static bool virtio_scsi_defer_to_dataplane(VirtIOSCSI *s) +{ + if (!s->ctx || s->dataplane_started) { + return false; + } + + virtio_device_start_ioeventfd(&s->parent_obj.parent_obj); + return !s->dataplane_fenced; +} + static void virtio_scsi_handle_ctrl(VirtIODevice *vdev, VirtQueue *vq) { VirtIOSCSI *s = (VirtIOSCSI *)vdev; - if (s->ctx) { - virtio_device_start_ioeventfd(vdev); - if (!s->dataplane_fenced) { - return; - } + if (virtio_scsi_defer_to_dataplane(s)) { + return; } + virtio_scsi_acquire(s); virtio_scsi_handle_ctrl_vq(s, vq); virtio_scsi_release(s); @@ -720,12 +736,10 @@ static void virtio_scsi_handle_cmd(VirtIODevice *vdev, VirtQueue *vq) /* use non-QOM casts in the data path */ VirtIOSCSI *s = (VirtIOSCSI *)vdev; - if (s->ctx && !s->dataplane_started) { - virtio_device_start_ioeventfd(vdev); - if (!s->dataplane_fenced) { - return; - } + if (virtio_scsi_defer_to_dataplane(s)) { + return; } + virtio_scsi_acquire(s); virtio_scsi_handle_cmd_vq(s, vq); virtio_scsi_release(s); @@ -855,12 +869,10 @@ static void virtio_scsi_handle_event(VirtIODevice *vdev, VirtQueue *vq) { VirtIOSCSI *s = VIRTIO_SCSI(vdev); - if (s->ctx) { - virtio_device_start_ioeventfd(vdev); - if (!s->dataplane_fenced) { - return; - } + if (virtio_scsi_defer_to_dataplane(s)) { + return; } + virtio_scsi_acquire(s); virtio_scsi_handle_event_vq(s, vq); virtio_scsi_release(s); -- 2.31.1