1 /*
2  * Virtio SCSI dataplane
3  *
4  * Copyright Red Hat, Inc. 2014
5  *
6  * Authors:
7  *   Fam Zheng <famz@redhat.com>
8  *
9  * This work is licensed under the terms of the GNU GPL, version 2 or later.
10  * See the COPYING file in the top-level directory.
11  *
12  */
13 
14 #include "qemu/osdep.h"
15 #include "qapi/error.h"
16 #include "hw/virtio/virtio-scsi.h"
17 #include "qemu/error-report.h"
18 #include "sysemu/block-backend.h"
19 #include "hw/scsi/scsi.h"
20 #include "scsi/constants.h"
21 #include "hw/virtio/virtio-bus.h"
22 
23 /* Context: QEMU global mutex held */
24 void virtio_scsi_dataplane_setup(VirtIOSCSI *s, Error **errp)
25 {
26     VirtIOSCSICommon *vs = VIRTIO_SCSI_COMMON(s);
27     VirtIODevice *vdev = VIRTIO_DEVICE(s);
28     BusState *qbus = qdev_get_parent_bus(DEVICE(vdev));
29     VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
30 
31     if (vs->conf.iothread) {
32         if (!k->set_guest_notifiers || !k->ioeventfd_assign) {
33             error_setg(errp,
34                        "device is incompatible with iothread "
35                        "(transport does not support notifiers)");
36             return;
37         }
38         if (!virtio_device_ioeventfd_enabled(vdev)) {
39             error_setg(errp, "ioeventfd is required for iothread");
40             return;
41         }
42         s->ctx = iothread_get_aio_context(vs->conf.iothread);
43     } else {
44         if (!virtio_device_ioeventfd_enabled(vdev)) {
45             return;
46         }
47         s->ctx = qemu_get_aio_context();
48     }
49 }
50 
51 static int virtio_scsi_set_host_notifier(VirtIOSCSI *s, VirtQueue *vq, int n)
52 {
53     BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(s)));
54     int rc;
55 
56     /* Set up virtqueue notify */
57     rc = virtio_bus_set_host_notifier(VIRTIO_BUS(qbus), n, true);
58     if (rc != 0) {
59         fprintf(stderr, "virtio-scsi: Failed to set host notifier (%d)\n",
60                 rc);
61         s->dataplane_fenced = true;
62         return rc;
63     }
64 
65     return 0;
66 }
67 
68 /* Context: BH in IOThread */
69 static void virtio_scsi_dataplane_stop_bh(void *opaque)
70 {
71     VirtIOSCSI *s = opaque;
72     VirtIOSCSICommon *vs = VIRTIO_SCSI_COMMON(s);
73     EventNotifier *host_notifier;
74     int i;
75 
76     virtio_queue_aio_detach_host_notifier(vs->ctrl_vq, s->ctx);
77     host_notifier = virtio_queue_get_host_notifier(vs->ctrl_vq);
78 
79     /*
80      * Test and clear notifier after disabling event, in case poll callback
81      * didn't have time to run.
82      */
83     virtio_queue_host_notifier_read(host_notifier);
84 
85     virtio_queue_aio_detach_host_notifier(vs->event_vq, s->ctx);
86     host_notifier = virtio_queue_get_host_notifier(vs->event_vq);
87     virtio_queue_host_notifier_read(host_notifier);
88 
89     for (i = 0; i < vs->conf.num_queues; i++) {
90         virtio_queue_aio_detach_host_notifier(vs->cmd_vqs[i], s->ctx);
91         host_notifier = virtio_queue_get_host_notifier(vs->cmd_vqs[i]);
92         virtio_queue_host_notifier_read(host_notifier);
93     }
94 }
95 
96 /* Context: QEMU global mutex held */
97 int virtio_scsi_dataplane_start(VirtIODevice *vdev)
98 {
99     int i;
100     int rc;
101     int vq_init_count = 0;
102     BusState *qbus = qdev_get_parent_bus(DEVICE(vdev));
103     VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
104     VirtIOSCSICommon *vs = VIRTIO_SCSI_COMMON(vdev);
105     VirtIOSCSI *s = VIRTIO_SCSI(vdev);
106 
107     if (s->dataplane_started ||
108         s->dataplane_starting ||
109         s->dataplane_fenced) {
110         return 0;
111     }
112 
113     s->dataplane_starting = true;
114 
115     /* Set up guest notifier (irq) */
116     rc = k->set_guest_notifiers(qbus->parent, vs->conf.num_queues + 2, true);
117     if (rc != 0) {
118         error_report("virtio-scsi: Failed to set guest notifiers (%d), "
119                      "ensure -accel kvm is set.", rc);
120         goto fail_guest_notifiers;
121     }
122 
123     /*
124      * Batch all the host notifiers in a single transaction to avoid
125      * quadratic time complexity in address_space_update_ioeventfds().
126      */
127     memory_region_transaction_begin();
128 
129     rc = virtio_scsi_set_host_notifier(s, vs->ctrl_vq, 0);
130     if (rc != 0) {
131         goto fail_host_notifiers;
132     }
133 
134     vq_init_count++;
135     rc = virtio_scsi_set_host_notifier(s, vs->event_vq, 1);
136     if (rc != 0) {
137         goto fail_host_notifiers;
138     }
139 
140     vq_init_count++;
141 
142     for (i = 0; i < vs->conf.num_queues; i++) {
143         rc = virtio_scsi_set_host_notifier(s, vs->cmd_vqs[i], i + 2);
144         if (rc) {
145             goto fail_host_notifiers;
146         }
147         vq_init_count++;
148     }
149 
150     memory_region_transaction_commit();
151 
152     s->dataplane_starting = false;
153     s->dataplane_started = true;
154     smp_wmb(); /* paired with aio_notify_accept() */
155 
156     if (s->bus.drain_count == 0) {
157         virtio_queue_aio_attach_host_notifier(vs->ctrl_vq, s->ctx);
158         virtio_queue_aio_attach_host_notifier_no_poll(vs->event_vq, s->ctx);
159 
160         for (i = 0; i < vs->conf.num_queues; i++) {
161             virtio_queue_aio_attach_host_notifier(vs->cmd_vqs[i], s->ctx);
162         }
163     }
164     return 0;
165 
166 fail_host_notifiers:
167     for (i = 0; i < vq_init_count; i++) {
168         virtio_bus_set_host_notifier(VIRTIO_BUS(qbus), i, false);
169     }
170 
171     /*
172      * The transaction expects the ioeventfds to be open when it
173      * commits. Do it now, before the cleanup loop.
174      */
175     memory_region_transaction_commit();
176 
177     for (i = 0; i < vq_init_count; i++) {
178         virtio_bus_cleanup_host_notifier(VIRTIO_BUS(qbus), i);
179     }
180     k->set_guest_notifiers(qbus->parent, vs->conf.num_queues + 2, false);
181 fail_guest_notifiers:
182     s->dataplane_fenced = true;
183     s->dataplane_starting = false;
184     s->dataplane_started = true;
185     return -ENOSYS;
186 }
187 
188 /* Context: QEMU global mutex held */
189 void virtio_scsi_dataplane_stop(VirtIODevice *vdev)
190 {
191     BusState *qbus = qdev_get_parent_bus(DEVICE(vdev));
192     VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
193     VirtIOSCSICommon *vs = VIRTIO_SCSI_COMMON(vdev);
194     VirtIOSCSI *s = VIRTIO_SCSI(vdev);
195     int i;
196 
197     if (!s->dataplane_started || s->dataplane_stopping) {
198         return;
199     }
200 
201     /* Better luck next time. */
202     if (s->dataplane_fenced) {
203         s->dataplane_fenced = false;
204         s->dataplane_started = false;
205         return;
206     }
207     s->dataplane_stopping = true;
208 
209     if (s->bus.drain_count == 0) {
210         aio_wait_bh_oneshot(s->ctx, virtio_scsi_dataplane_stop_bh, s);
211     }
212 
213     blk_drain_all(); /* ensure there are no in-flight requests */
214 
215     /*
216      * Batch all the host notifiers in a single transaction to avoid
217      * quadratic time complexity in address_space_update_ioeventfds().
218      */
219     memory_region_transaction_begin();
220 
221     for (i = 0; i < vs->conf.num_queues + 2; i++) {
222         virtio_bus_set_host_notifier(VIRTIO_BUS(qbus), i, false);
223     }
224 
225     /*
226      * The transaction expects the ioeventfds to be open when it
227      * commits. Do it now, before the cleanup loop.
228      */
229     memory_region_transaction_commit();
230 
231     for (i = 0; i < vs->conf.num_queues + 2; i++) {
232         virtio_bus_cleanup_host_notifier(VIRTIO_BUS(qbus), i);
233     }
234 
235     /* Clean up guest notifier (irq) */
236     k->set_guest_notifiers(qbus->parent, vs->conf.num_queues + 2, false);
237     s->dataplane_stopping = false;
238     s->dataplane_started = false;
239 }
240