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 "hw/virtio/virtio-scsi.h"
15 #include "qemu/error-report.h"
16 #include "sysemu/block-backend.h"
17 #include <hw/scsi/scsi.h>
18 #include <block/scsi.h>
19 #include <hw/virtio/virtio-bus.h>
20 #include "hw/virtio/virtio-access.h"
21 #include "stdio.h"
22 
23 /* Context: QEMU global mutex held */
24 void virtio_scsi_set_iothread(VirtIOSCSI *s, IOThread *iothread)
25 {
26     BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(s)));
27     VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
28     VirtIOSCSICommon *vs = VIRTIO_SCSI_COMMON(s);
29 
30     assert(!s->ctx);
31     s->ctx = iothread_get_aio_context(vs->conf.iothread);
32 
33     /* Don't try if transport does not support notifiers. */
34     if (!k->set_guest_notifiers || !k->set_host_notifier) {
35         fprintf(stderr, "virtio-scsi: Failed to set iothread "
36                    "(transport does not support notifiers)");
37         exit(1);
38     }
39 }
40 
41 static VirtIOSCSIVring *virtio_scsi_vring_init(VirtIOSCSI *s,
42                                                VirtQueue *vq,
43                                                EventNotifierHandler *handler,
44                                                int n)
45 {
46     BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(s)));
47     VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
48     VirtIOSCSIVring *r;
49     int rc;
50 
51     /* Set up virtqueue notify */
52     rc = k->set_host_notifier(qbus->parent, n, true);
53     if (rc != 0) {
54         fprintf(stderr, "virtio-scsi: Failed to set host notifier (%d)\n",
55                 rc);
56         s->dataplane_fenced = true;
57         return NULL;
58     }
59 
60     r = g_new(VirtIOSCSIVring, 1);
61     r->host_notifier = *virtio_queue_get_host_notifier(vq);
62     r->guest_notifier = *virtio_queue_get_guest_notifier(vq);
63     aio_set_event_notifier(s->ctx, &r->host_notifier, true, handler);
64 
65     r->parent = s;
66 
67     if (!vring_setup(&r->vring, VIRTIO_DEVICE(s), n)) {
68         fprintf(stderr, "virtio-scsi: VRing setup failed\n");
69         goto fail_vring;
70     }
71     return r;
72 
73 fail_vring:
74     aio_set_event_notifier(s->ctx, &r->host_notifier, true, NULL);
75     k->set_host_notifier(qbus->parent, n, false);
76     g_free(r);
77     return NULL;
78 }
79 
80 VirtIOSCSIReq *virtio_scsi_pop_req_vring(VirtIOSCSI *s,
81                                          VirtIOSCSIVring *vring)
82 {
83     VirtIOSCSIReq *req = virtio_scsi_init_req(s, NULL);
84     int r;
85 
86     req->vring = vring;
87     r = vring_pop((VirtIODevice *)s, &vring->vring, &req->elem);
88     if (r < 0) {
89         virtio_scsi_free_req(req);
90         req = NULL;
91     }
92     return req;
93 }
94 
95 void virtio_scsi_vring_push_notify(VirtIOSCSIReq *req)
96 {
97     VirtIODevice *vdev = VIRTIO_DEVICE(req->vring->parent);
98 
99     vring_push(vdev, &req->vring->vring, &req->elem,
100                req->qsgl.size + req->resp_iov.size);
101 
102     if (vring_should_notify(vdev, &req->vring->vring)) {
103         event_notifier_set(&req->vring->guest_notifier);
104     }
105 }
106 
107 static void virtio_scsi_iothread_handle_ctrl(EventNotifier *notifier)
108 {
109     VirtIOSCSIVring *vring = container_of(notifier,
110                                           VirtIOSCSIVring, host_notifier);
111     VirtIOSCSI *s = VIRTIO_SCSI(vring->parent);
112     VirtIOSCSIReq *req;
113 
114     event_notifier_test_and_clear(notifier);
115     while ((req = virtio_scsi_pop_req_vring(s, vring))) {
116         virtio_scsi_handle_ctrl_req(s, req);
117     }
118 }
119 
120 static void virtio_scsi_iothread_handle_event(EventNotifier *notifier)
121 {
122     VirtIOSCSIVring *vring = container_of(notifier,
123                                           VirtIOSCSIVring, host_notifier);
124     VirtIOSCSI *s = vring->parent;
125     VirtIODevice *vdev = VIRTIO_DEVICE(s);
126 
127     event_notifier_test_and_clear(notifier);
128 
129     if (!(vdev->status & VIRTIO_CONFIG_S_DRIVER_OK)) {
130         return;
131     }
132 
133     if (s->events_dropped) {
134         virtio_scsi_push_event(s, NULL, VIRTIO_SCSI_T_NO_EVENT, 0);
135     }
136 }
137 
138 static void virtio_scsi_iothread_handle_cmd(EventNotifier *notifier)
139 {
140     VirtIOSCSIVring *vring = container_of(notifier,
141                                           VirtIOSCSIVring, host_notifier);
142     VirtIOSCSI *s = (VirtIOSCSI *)vring->parent;
143     VirtIOSCSIReq *req, *next;
144     QTAILQ_HEAD(, VirtIOSCSIReq) reqs = QTAILQ_HEAD_INITIALIZER(reqs);
145 
146     event_notifier_test_and_clear(notifier);
147     while ((req = virtio_scsi_pop_req_vring(s, vring))) {
148         if (virtio_scsi_handle_cmd_req_prepare(s, req)) {
149             QTAILQ_INSERT_TAIL(&reqs, req, next);
150         }
151     }
152 
153     QTAILQ_FOREACH_SAFE(req, &reqs, next, next) {
154         virtio_scsi_handle_cmd_req_submit(s, req);
155     }
156 }
157 
158 /* assumes s->ctx held */
159 static void virtio_scsi_clear_aio(VirtIOSCSI *s)
160 {
161     VirtIOSCSICommon *vs = VIRTIO_SCSI_COMMON(s);
162     int i;
163 
164     if (s->ctrl_vring) {
165         aio_set_event_notifier(s->ctx, &s->ctrl_vring->host_notifier,
166                                true, NULL);
167     }
168     if (s->event_vring) {
169         aio_set_event_notifier(s->ctx, &s->event_vring->host_notifier,
170                                true, NULL);
171     }
172     if (s->cmd_vrings) {
173         for (i = 0; i < vs->conf.num_queues && s->cmd_vrings[i]; i++) {
174             aio_set_event_notifier(s->ctx, &s->cmd_vrings[i]->host_notifier,
175                                    true, NULL);
176         }
177     }
178 }
179 
180 static void virtio_scsi_vring_teardown(VirtIOSCSI *s)
181 {
182     VirtIODevice *vdev = VIRTIO_DEVICE(s);
183     VirtIOSCSICommon *vs = VIRTIO_SCSI_COMMON(s);
184     int i;
185 
186     if (s->ctrl_vring) {
187         vring_teardown(&s->ctrl_vring->vring, vdev, 0);
188         g_free(s->ctrl_vring);
189         s->ctrl_vring = NULL;
190     }
191     if (s->event_vring) {
192         vring_teardown(&s->event_vring->vring, vdev, 1);
193         g_free(s->event_vring);
194         s->event_vring = NULL;
195     }
196     if (s->cmd_vrings) {
197         for (i = 0; i < vs->conf.num_queues && s->cmd_vrings[i]; i++) {
198             vring_teardown(&s->cmd_vrings[i]->vring, vdev, 2 + i);
199             g_free(s->cmd_vrings[i]);
200             s->cmd_vrings[i] = NULL;
201         }
202         free(s->cmd_vrings);
203         s->cmd_vrings = NULL;
204     }
205 }
206 
207 /* Context: QEMU global mutex held */
208 void virtio_scsi_dataplane_start(VirtIOSCSI *s)
209 {
210     int i;
211     int rc;
212     BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(s)));
213     VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
214     VirtIOSCSICommon *vs = VIRTIO_SCSI_COMMON(s);
215 
216     if (s->dataplane_started ||
217         s->dataplane_starting ||
218         s->dataplane_fenced ||
219         s->ctx != iothread_get_aio_context(vs->conf.iothread)) {
220         return;
221     }
222 
223     s->dataplane_starting = true;
224 
225     /* Set up guest notifier (irq) */
226     rc = k->set_guest_notifiers(qbus->parent, vs->conf.num_queues + 2, true);
227     if (rc != 0) {
228         fprintf(stderr, "virtio-scsi: Failed to set guest notifiers (%d), "
229                 "ensure -enable-kvm is set\n", rc);
230         s->dataplane_fenced = true;
231         goto fail_guest_notifiers;
232     }
233 
234     aio_context_acquire(s->ctx);
235     s->ctrl_vring = virtio_scsi_vring_init(s, vs->ctrl_vq,
236                                            virtio_scsi_iothread_handle_ctrl,
237                                            0);
238     if (!s->ctrl_vring) {
239         goto fail_vrings;
240     }
241     s->event_vring = virtio_scsi_vring_init(s, vs->event_vq,
242                                             virtio_scsi_iothread_handle_event,
243                                             1);
244     if (!s->event_vring) {
245         goto fail_vrings;
246     }
247     s->cmd_vrings = g_new(VirtIOSCSIVring *, vs->conf.num_queues);
248     for (i = 0; i < vs->conf.num_queues; i++) {
249         s->cmd_vrings[i] =
250             virtio_scsi_vring_init(s, vs->cmd_vqs[i],
251                                    virtio_scsi_iothread_handle_cmd,
252                                    i + 2);
253         if (!s->cmd_vrings[i]) {
254             goto fail_vrings;
255         }
256     }
257 
258     s->dataplane_starting = false;
259     s->dataplane_started = true;
260     aio_context_release(s->ctx);
261     return;
262 
263 fail_vrings:
264     virtio_scsi_clear_aio(s);
265     aio_context_release(s->ctx);
266     virtio_scsi_vring_teardown(s);
267     for (i = 0; i < vs->conf.num_queues + 2; i++) {
268         k->set_host_notifier(qbus->parent, i, false);
269     }
270     k->set_guest_notifiers(qbus->parent, vs->conf.num_queues + 2, false);
271 fail_guest_notifiers:
272     s->dataplane_starting = false;
273 }
274 
275 /* Context: QEMU global mutex held */
276 void virtio_scsi_dataplane_stop(VirtIOSCSI *s)
277 {
278     BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(s)));
279     VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
280     VirtIOSCSICommon *vs = VIRTIO_SCSI_COMMON(s);
281     int i;
282 
283     /* Better luck next time. */
284     if (s->dataplane_fenced) {
285         s->dataplane_fenced = false;
286         return;
287     }
288     if (!s->dataplane_started || s->dataplane_stopping) {
289         return;
290     }
291     s->dataplane_stopping = true;
292     assert(s->ctx == iothread_get_aio_context(vs->conf.iothread));
293 
294     aio_context_acquire(s->ctx);
295 
296     aio_set_event_notifier(s->ctx, &s->ctrl_vring->host_notifier,
297                            true, NULL);
298     aio_set_event_notifier(s->ctx, &s->event_vring->host_notifier,
299                            true, NULL);
300     for (i = 0; i < vs->conf.num_queues; i++) {
301         aio_set_event_notifier(s->ctx, &s->cmd_vrings[i]->host_notifier,
302                                true, NULL);
303     }
304 
305     blk_drain_all(); /* ensure there are no in-flight requests */
306 
307     aio_context_release(s->ctx);
308 
309     /* Sync vring state back to virtqueue so that non-dataplane request
310      * processing can continue when we disable the host notifier below.
311      */
312     virtio_scsi_vring_teardown(s);
313 
314     for (i = 0; i < vs->conf.num_queues + 2; i++) {
315         k->set_host_notifier(qbus->parent, i, false);
316     }
317 
318     /* Clean up guest notifier (irq) */
319     k->set_guest_notifiers(qbus->parent, vs->conf.num_queues + 2, false);
320     s->dataplane_stopping = false;
321     s->dataplane_started = false;
322 }
323