diff options
Diffstat (limited to 'app-emulation/qemu/files/qemu-7.0.0-virtio-scsi-fixes.patch')
| -rw-r--r-- | app-emulation/qemu/files/qemu-7.0.0-virtio-scsi-fixes.patch | 182 |
1 files changed, 182 insertions, 0 deletions
diff --git a/app-emulation/qemu/files/qemu-7.0.0-virtio-scsi-fixes.patch b/app-emulation/qemu/files/qemu-7.0.0-virtio-scsi-fixes.patch new file mode 100644 index 000000000000..9ec6ede80896 --- /dev/null +++ b/app-emulation/qemu/files/qemu-7.0.0-virtio-scsi-fixes.patch @@ -0,0 +1,182 @@ +https://bugs.gentoo.org/849500 +https://gitlab.com/qemu-project/qemu/-/commit/2f743ef6366c2df4ef51ef3ae318138cdc0125ab.patch +https://gitlab.com/qemu-project/qemu/-/commit/38738f7dbbda90fbc161757b7f4be35b52205552.patch + +From: Stefan Hajnoczi <stefanha@redhat.com> +Date: Wed, 27 Apr 2022 15:35:36 +0100 +Subject: [PATCH] virtio-scsi: fix ctrl and event handler functions in + dataplane mode + +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 <stefanha@redhat.com> +Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> +Message-id: 20220427143541.119567-2-stefanha@redhat.com +[Fixed s/by used/be used/ typo pointed out by Michael Tokarev +<mjt@tls.msk.ru>. +--Stefan] +Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> +--- 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); +GitLab + +From: Stefan Hajnoczi <stefanha@redhat.com> +Date: Wed, 27 Apr 2022 15:35:37 +0100 +Subject: [PATCH] virtio-scsi: don't waste CPU polling the event virtqueue + +The virtio-scsi event virtqueue is not emptied by its handler function. +This is typical for rx virtqueues where the device uses buffers when +some event occurs (e.g. a packet is received, an error condition +happens, etc). + +Polling non-empty virtqueues wastes CPU cycles. We are not waiting for +new buffers to become available, we are waiting for an event to occur, +so it's a misuse of CPU resources to poll for buffers. + +Introduce the new virtio_queue_aio_attach_host_notifier_no_poll() API, +which is identical to virtio_queue_aio_attach_host_notifier() except +that it does not poll the virtqueue. + +Before this patch the following command-line consumed 100% CPU in the +IOThread polling and calling virtio_scsi_handle_event(): + + $ qemu-system-x86_64 -M accel=kvm -m 1G -cpu host \ + --object iothread,id=iothread0 \ + --device virtio-scsi-pci,iothread=iothread0 \ + --blockdev file,filename=test.img,aio=native,cache.direct=on,node-name=drive0 \ + --device scsi-hd,drive=drive0 + +After this patch CPU is no longer wasted. + +Reported-by: Nir Soffer <nsoffer@redhat.com> +Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> +Tested-by: Nir Soffer <nsoffer@redhat.com> +Message-id: 20220427143541.119567-3-stefanha@redhat.com +Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> +--- a/hw/scsi/virtio-scsi-dataplane.c ++++ b/hw/scsi/virtio-scsi-dataplane.c +@@ -138,7 +138,7 @@ int virtio_scsi_dataplane_start(VirtIODevice *vdev) + + aio_context_acquire(s->ctx); + virtio_queue_aio_attach_host_notifier(vs->ctrl_vq, s->ctx); +- virtio_queue_aio_attach_host_notifier(vs->event_vq, s->ctx); ++ virtio_queue_aio_attach_host_notifier_no_poll(vs->event_vq, s->ctx); + + for (i = 0; i < vs->conf.num_queues; i++) { + virtio_queue_aio_attach_host_notifier(vs->cmd_vqs[i], s->ctx); +--- a/hw/virtio/virtio.c ++++ b/hw/virtio/virtio.c +@@ -3534,6 +3534,19 @@ void virtio_queue_aio_attach_host_notifier(VirtQueue *vq, AioContext *ctx) + virtio_queue_host_notifier_aio_poll_end); + } + ++/* ++ * Same as virtio_queue_aio_attach_host_notifier() but without polling. Use ++ * this for rx virtqueues and similar cases where the virtqueue handler ++ * function does not pop all elements. When the virtqueue is left non-empty ++ * polling consumes CPU cycles and should not be used. ++ */ ++void virtio_queue_aio_attach_host_notifier_no_poll(VirtQueue *vq, AioContext *ctx) ++{ ++ aio_set_event_notifier(ctx, &vq->host_notifier, true, ++ virtio_queue_host_notifier_read, ++ NULL, NULL); ++} ++ + void virtio_queue_aio_detach_host_notifier(VirtQueue *vq, AioContext *ctx) + { + aio_set_event_notifier(ctx, &vq->host_notifier, true, NULL, NULL, NULL); +--- a/include/hw/virtio/virtio.h ++++ b/include/hw/virtio/virtio.h +@@ -317,6 +317,7 @@ EventNotifier *virtio_queue_get_host_notifier(VirtQueue *vq); + void virtio_queue_set_host_notifier_enabled(VirtQueue *vq, bool enabled); + void virtio_queue_host_notifier_read(EventNotifier *n); + void virtio_queue_aio_attach_host_notifier(VirtQueue *vq, AioContext *ctx); ++void virtio_queue_aio_attach_host_notifier_no_poll(VirtQueue *vq, AioContext *ctx); + void virtio_queue_aio_detach_host_notifier(VirtQueue *vq, AioContext *ctx); + VirtQueue *virtio_vector_first_queue(VirtIODevice *vdev, uint16_t vector); + VirtQueue *virtio_vector_next_queue(VirtQueue *vq); +GitLab |