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Re: [Qemu-devel] [RFC PATCH v2 09/10] virtio-scsi-dataplane: Code to run
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [RFC PATCH v2 09/10] virtio-scsi-dataplane: Code to run virtio-scsi on iothread |
Date: |
Fri, 19 Sep 2014 11:29:32 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.0 |
Il 06/08/2014 07:35, Fam Zheng ha scritto:
> This implements the core part of dataplane feature of virtio-scsi.
>
> A few fields are added in VirtIOSCSICommon to maintain the dataplane
> status. These fields are managed by a new source file:
> virtio-scsi-dataplane.c.
>
> Most code in this file will run on an iothread, unless otherwise
> commented as in a global mutex context, such as those functions to
> start, stop and setting the iothread property.
>
> Upon start, we set up guest/host event notifiers, in a same way as
> virtio-blk does. The handlers then pop request from vring and call into
> virtio-scsi.c functions to process it. So we need to make sure make all
> those called functions work with iothread, too.
>
> Signed-off-by: Fam Zheng <address@hidden>
> ---
> hw/scsi/Makefile.objs | 2 +-
> hw/scsi/virtio-scsi-dataplane.c | 219
> ++++++++++++++++++++++++++++++++++++++++
> include/hw/virtio/virtio-scsi.h | 19 ++++
> 3 files changed, 239 insertions(+), 1 deletion(-)
> create mode 100644 hw/scsi/virtio-scsi-dataplane.c
>
> diff --git a/hw/scsi/Makefile.objs b/hw/scsi/Makefile.objs
> index 121ddc5..40c79d3 100644
> --- a/hw/scsi/Makefile.objs
> +++ b/hw/scsi/Makefile.objs
> @@ -8,6 +8,6 @@ common-obj-$(CONFIG_ESP_PCI) += esp-pci.o
> obj-$(CONFIG_PSERIES) += spapr_vscsi.o
>
> ifeq ($(CONFIG_VIRTIO),y)
> -obj-y += virtio-scsi.o
> +obj-y += virtio-scsi.o virtio-scsi-dataplane.o
> obj-$(CONFIG_VHOST_SCSI) += vhost-scsi.o
> endif
> diff --git a/hw/scsi/virtio-scsi-dataplane.c b/hw/scsi/virtio-scsi-dataplane.c
> new file mode 100644
> index 0000000..d077b67
> --- /dev/null
> +++ b/hw/scsi/virtio-scsi-dataplane.c
> @@ -0,0 +1,219 @@
> +/*
> + * Virtio SCSI dataplane
> + *
> + * Copyright Red Hat, Inc. 2014
> + *
> + * Authors:
> + * Fam Zheng <address@hidden>
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or later.
> + * See the COPYING file in the top-level directory.
> + *
> + */
> +
> +#include "hw/virtio/virtio-scsi.h"
> +#include "qemu/error-report.h"
> +#include <hw/scsi/scsi.h>
> +#include <block/scsi.h>
> +#include <hw/virtio/virtio-bus.h>
> +#include "hw/virtio/virtio-access.h"
> +#include "stdio.h"
> +
> +/* Context: QEMU global mutex held */
> +void virtio_scsi_set_iothread(VirtIOSCSICommon *s, IOThread *iothread)
> +{
> + BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(s)));
> + VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
> +
> + s->ctx = iothread_get_aio_context(s->conf.iothread);
assert that it's NULL?
> +
> + /* Don't try if transport does not support notifiers. */
> + if (!k->set_guest_notifiers || !k->set_host_notifier) {
> + fprintf(stderr, "virtio-scsi: Failed to set iothread "
> + "(transport does not support notifiers)");
> + exit(1);
> + }
> +}
> +
> +static VirtIOSCSIVring *virtio_scsi_vring_init(VirtIOSCSICommon *s,
> + VirtQueue *vq,
> + EventNotifierHandler *handler,
> + int n)
> +{
> + BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(s)));
> + VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
> + VirtIOSCSIVring *r = g_slice_new(VirtIOSCSIVring);
> +
> + /* Set up virtqueue notify */
> + if (k->set_host_notifier(qbus->parent, n, true) != 0) {
> + fprintf(stderr, "virtio-scsi: Failed to set host notifier\n");
> + exit(1);
> + }
> + r->host_notifier = *virtio_queue_get_host_notifier(vq);
> + r->guest_notifier = *virtio_queue_get_guest_notifier(vq);
> + aio_set_event_notifier(s->ctx, &r->host_notifier, handler);
> +
> + r->parent = s;
> +
> + if (!vring_setup(&r->vring, VIRTIO_DEVICE(s), n)) {
> + fprintf(stderr, "virtio-scsi: VRing setup failed\n");
> + exit(1);
> + }
> + return r;
> +}
> +
> +VirtIOSCSIReq *virtio_scsi_pop_req_vring(VirtIOSCSI *s,
> + VirtIOSCSIVring *vring)
> +{
> + VirtIOSCSIReq *req = virtio_scsi_init_req(s, NULL);
> + int r;
> +
> + req->vring = vring;
> + r = vring_pop((VirtIODevice *)s, &vring->vring, &req->elem);
> + if (r < 0) {
> + virtio_scsi_free_req(req);
> + req = NULL;
> + }
> + return req;
> +}
> +
> +void virtio_scsi_vring_push_notify(VirtIOSCSIReq *req)
> +{
> + vring_push(&req->vring->vring, &req->elem,
> + req->qsgl.size + req->resp_iov.size);
> + event_notifier_set(&req->vring->guest_notifier);
> +}
> +
> +static void virtio_scsi_iothread_handle_ctrl(EventNotifier *notifier)
> +{
> + VirtIOSCSIVring *vring = container_of(notifier,
> + VirtIOSCSIVring, host_notifier);
> + VirtIOSCSI *s = VIRTIO_SCSI(vring->parent);
> + VirtIOSCSIReq *req;
> +
> + event_notifier_test_and_clear(notifier);
> + while ((req = virtio_scsi_pop_req_vring(s, vring))) {
> + virtio_scsi_handle_ctrl_req(s, req);
> + }
> +}
> +
> +static void virtio_scsi_iothread_handle_event(EventNotifier *notifier)
> +{
> + VirtIOSCSIVring *vring = container_of(notifier,
> + VirtIOSCSIVring, host_notifier);
> + VirtIOSCSICommon *vs = vring->parent;
> + VirtIOSCSI *s = VIRTIO_SCSI(vs);
> + VirtIODevice *vdev = VIRTIO_DEVICE(s);
> +
> + event_notifier_test_and_clear(notifier);
> +
> + if (!(vdev->status & VIRTIO_CONFIG_S_DRIVER_OK)) {
> + return;
> + }
> +
> + if (s->events_dropped) {
> + virtio_scsi_push_event(s, NULL, VIRTIO_SCSI_T_NO_EVENT, 0);
> + }
> +}
> +
> +static void virtio_scsi_iothread_handle_cmd(EventNotifier *notifier)
> +{
> + VirtIOSCSIVring *vring = container_of(notifier,
> + VirtIOSCSIVring, host_notifier);
> + VirtIOSCSI *s = VIRTIO_SCSI(vring->parent);
> + VirtIOSCSIReq *req;
> +
> + event_notifier_test_and_clear(notifier);
> + while ((req = virtio_scsi_pop_req_vring(s, vring))) {
> + virtio_scsi_handle_cmd_req(s, req);
> + }
Perhaps add bdrv_io_plug/bdrv_io_unplug?
> +}
> +
> +/* Context: QEMU global mutex held */
> +void virtio_scsi_dataplane_start(VirtIOSCSICommon *s)
> +{
> + int i;
> + int rc;
> + BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(s)));
> + VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
> +
> + if (s->dataplane_started ||
> + s->dataplane_starting ||
> + s->ctx != iothread_get_aio_context(s->conf.iothread)) {
> + return;
> + }
> +
> + s->dataplane_starting = true;
Please do a bdrv_drain_all() here. Then you can set the contexts for
all children here too (for the hotplug case: in virtio_scsi_hotplug).
Then you do not have to do it in virtio_scsi_do_tmf and
virtio_scsi_handle_cmd_req.
> + /* Set up guest notifier (irq) */
> + rc = k->set_guest_notifiers(qbus->parent, s->conf.num_queues + 2, true);
> + if (rc != 0) {
> + fprintf(stderr, "virtio-scsi: Failed to set guest notifiers, "
> + "ensure -enable-kvm is set\n");
> + exit(1);
> + }
> +
> + aio_context_acquire(s->ctx);
> + s->ctrl_vring = virtio_scsi_vring_init(s, s->ctrl_vq,
> + virtio_scsi_iothread_handle_ctrl,
> + 0);
> + s->event_vring = virtio_scsi_vring_init(s, s->event_vq,
> +
> virtio_scsi_iothread_handle_event,
> + 1);
> + s->cmd_vrings = g_malloc0(sizeof(VirtIOSCSIVring) * s->conf.num_queues);
> + for (i = 0; i < s->conf.num_queues; i++) {
> + s->cmd_vrings[i] =
> + virtio_scsi_vring_init(s, s->cmd_vqs[i],
> + virtio_scsi_iothread_handle_cmd,
> + i + 2);
> + }
> +
> + aio_context_release(s->ctx);
> + s->dataplane_starting = false;
> + s->dataplane_started = true;
> +}
> +
> +/* Context: QEMU global mutex held */
> +void virtio_scsi_dataplane_stop(VirtIOSCSICommon *s)
> +{
> + BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(s)));
> + VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
> + VirtIODevice *vdev = VIRTIO_DEVICE(s);
> + int i;
> +
> + if (!s->dataplane_started || s->dataplane_stopping) {
> + return;
> + }
> + s->dataplane_stopping = true;
> + assert(s->ctx == iothread_get_aio_context(s->conf.iothread));
> +
> + aio_context_acquire(s->ctx);
> +
> + aio_set_event_notifier(s->ctx, &s->ctrl_vring->host_notifier, NULL);
> + aio_set_event_notifier(s->ctx, &s->event_vring->host_notifier, NULL);
> + for (i = 0; i < s->conf.num_queues; i++) {
> + aio_set_event_notifier(s->ctx, &s->cmd_vrings[i]->host_notifier,
> NULL);
> + }
> +
> + bdrv_drain_all(); /* ensure there are no in-flight requests */
> +
> + aio_context_release(s->ctx);
> +
> + /* Sync vring state back to virtqueue so that non-dataplane request
> + * processing can continue when we disable the host notifier below.
> + */
> + vring_teardown(&s->ctrl_vring->vring, vdev, 0);
> + vring_teardown(&s->event_vring->vring, vdev, 1);
> + for (i = 0; i < s->conf.num_queues; i++) {
> + vring_teardown(&s->cmd_vrings[i]->vring, vdev, 2 + i);
> + }
> +
> + for (i = 0; i < s->conf.num_queues + 2; i++) {
> + k->set_host_notifier(qbus->parent, i, false);
> + }
> +
> + /* Clean up guest notifier (irq) */
> + k->set_guest_notifiers(qbus->parent, s->conf.num_queues + 2, false);
> + s->dataplane_stopping = false;
> + s->dataplane_started = false;
> +}
> diff --git a/include/hw/virtio/virtio-scsi.h b/include/hw/virtio/virtio-scsi.h
> index 6f92c29..b9f2197 100644
> --- a/include/hw/virtio/virtio-scsi.h
> +++ b/include/hw/virtio/virtio-scsi.h
> @@ -174,6 +174,18 @@ typedef struct VirtIOSCSICommon {
> VirtQueue *ctrl_vq;
> VirtQueue *event_vq;
> VirtQueue **cmd_vqs;
> +
> + /* Fields for dataplane below */
> + AioContext *ctx; /* one iothread per virtio-scsi-pci for now */
> +
> + /* Vring is used instead of vq in dataplane code, because of the
> underlying
> + * memory layer thread safety */
> + VirtIOSCSIVring *ctrl_vring;
> + VirtIOSCSIVring *event_vring;
> + VirtIOSCSIVring **cmd_vrings;
> + bool dataplane_started;
> + bool dataplane_starting;
> + bool dataplane_stopping;
Please add these to VirtIOSCSI rather than VirtIOSCSICommon. Same for
the new functions you declare below.
Paolo
> } VirtIOSCSICommon;
>
> typedef struct {
> @@ -239,4 +251,11 @@ void virtio_scsi_free_req(VirtIOSCSIReq *req);
> void virtio_scsi_push_event(VirtIOSCSI *s, SCSIDevice *dev,
> uint32_t event, uint32_t reason);
>
> +void virtio_scsi_set_iothread(VirtIOSCSICommon *s, IOThread *iothread);
> +void virtio_scsi_dataplane_start(VirtIOSCSICommon *s);
> +void virtio_scsi_dataplane_stop(VirtIOSCSICommon *s);
> +void virtio_scsi_vring_push_notify(VirtIOSCSIReq *req);
> +VirtIOSCSIReq *virtio_scsi_pop_req_vring(VirtIOSCSI *s,
> + VirtIOSCSIVring *vring);
> +
> #endif /* _QEMU_VIRTIO_SCSI_H */
>
- Re: [Qemu-devel] [RFC PATCH v2 09/10] virtio-scsi-dataplane: Code to run virtio-scsi on iothread,
Paolo Bonzini <=