xref: /qemu/hw/9pfs/xen-9p-backend.c (revision dcc474c6) 
1 /*
2  * Xen 9p backend
3  *
4  * Copyright Aporeto 2017
5  *
6  * Authors:
7  *  Stefano Stabellini <stefano@aporeto.com>
8  *
9  */
10 
11 #include "qemu/osdep.h"
12 
13 #include "hw/9pfs/9p.h"
14 #include "hw/xen/xen-legacy-backend.h"
15 #include "hw/9pfs/xen-9pfs.h"
16 #include "qapi/error.h"
17 #include "qemu/config-file.h"
18 #include "qemu/main-loop.h"
19 #include "qemu/option.h"
20 #include "fsdev/qemu-fsdev.h"
21 
22 #define VERSIONS "1"
23 #define MAX_RINGS 8
24 #define MAX_RING_ORDER 8
25 
26 typedef struct Xen9pfsRing {
27     struct Xen9pfsDev *priv;
28 
29     int ref;
30     xenevtchn_handle   *evtchndev;
31     int evtchn;
32     int local_port;
33     int ring_order;
34     struct xen_9pfs_data_intf *intf;
35     unsigned char *data;
36     struct xen_9pfs_data ring;
37 
38     struct iovec *sg;
39     QEMUBH *bh;
40 
41     /* local copies, so that we can read/write PDU data directly from
42      * the ring */
43     RING_IDX out_cons, out_size, in_cons;
44     bool inprogress;
45 } Xen9pfsRing;
46 
47 typedef struct Xen9pfsDev {
48     struct XenLegacyDevice xendev;  /* must be first */
49     V9fsState state;
50     char *path;
51     char *security_model;
52     char *tag;
53     char *id;
54 
55     int num_rings;
56     Xen9pfsRing *rings;
57 } Xen9pfsDev;
58 
59 static void xen_9pfs_disconnect(struct XenLegacyDevice *xendev);
60 
61 static void xen_9pfs_in_sg(Xen9pfsRing *ring,
62                            struct iovec *in_sg,
63                            int *num,
64                            uint32_t idx,
65                            uint32_t size)
66 {
67     RING_IDX cons, prod, masked_prod, masked_cons;
68 
69     cons = ring->intf->in_cons;
70     prod = ring->intf->in_prod;
71     xen_rmb();
72     masked_prod = xen_9pfs_mask(prod, XEN_FLEX_RING_SIZE(ring->ring_order));
73     masked_cons = xen_9pfs_mask(cons, XEN_FLEX_RING_SIZE(ring->ring_order));
74 
75     if (masked_prod < masked_cons) {
76         in_sg[0].iov_base = ring->ring.in + masked_prod;
77         in_sg[0].iov_len = masked_cons - masked_prod;
78         *num = 1;
79     } else {
80         in_sg[0].iov_base = ring->ring.in + masked_prod;
81         in_sg[0].iov_len = XEN_FLEX_RING_SIZE(ring->ring_order) - masked_prod;
82         in_sg[1].iov_base = ring->ring.in;
83         in_sg[1].iov_len = masked_cons;
84         *num = 2;
85     }
86 }
87 
88 static void xen_9pfs_out_sg(Xen9pfsRing *ring,
89                             struct iovec *out_sg,
90                             int *num,
91                             uint32_t idx)
92 {
93     RING_IDX cons, prod, masked_prod, masked_cons;
94 
95     cons = ring->intf->out_cons;
96     prod = ring->intf->out_prod;
97     xen_rmb();
98     masked_prod = xen_9pfs_mask(prod, XEN_FLEX_RING_SIZE(ring->ring_order));
99     masked_cons = xen_9pfs_mask(cons, XEN_FLEX_RING_SIZE(ring->ring_order));
100 
101     if (masked_cons < masked_prod) {
102         out_sg[0].iov_base = ring->ring.out + masked_cons;
103         out_sg[0].iov_len = ring->out_size;
104         *num = 1;
105     } else {
106         if (ring->out_size >
107             (XEN_FLEX_RING_SIZE(ring->ring_order) - masked_cons)) {
108             out_sg[0].iov_base = ring->ring.out + masked_cons;
109             out_sg[0].iov_len = XEN_FLEX_RING_SIZE(ring->ring_order) -
110                                 masked_cons;
111             out_sg[1].iov_base = ring->ring.out;
112             out_sg[1].iov_len = ring->out_size -
113                                 (XEN_FLEX_RING_SIZE(ring->ring_order) -
114                                  masked_cons);
115             *num = 2;
116         } else {
117             out_sg[0].iov_base = ring->ring.out + masked_cons;
118             out_sg[0].iov_len = ring->out_size;
119             *num = 1;
120         }
121     }
122 }
123 
124 static ssize_t xen_9pfs_pdu_vmarshal(V9fsPDU *pdu,
125                                      size_t offset,
126                                      const char *fmt,
127                                      va_list ap)
128 {
129     Xen9pfsDev *xen_9pfs = container_of(pdu->s, Xen9pfsDev, state);
130     struct iovec in_sg[2];
131     int num;
132     ssize_t ret;
133 
134     xen_9pfs_in_sg(&xen_9pfs->rings[pdu->tag % xen_9pfs->num_rings],
135                    in_sg, &num, pdu->idx, ROUND_UP(offset + 128, 512));
136 
137     ret = v9fs_iov_vmarshal(in_sg, num, offset, 0, fmt, ap);
138     if (ret < 0) {
139         xen_pv_printf(&xen_9pfs->xendev, 0,
140                       "Failed to encode VirtFS request type %d\n", pdu->id + 1);
141         xen_be_set_state(&xen_9pfs->xendev, XenbusStateClosing);
142         xen_9pfs_disconnect(&xen_9pfs->xendev);
143     }
144     return ret;
145 }
146 
147 static ssize_t xen_9pfs_pdu_vunmarshal(V9fsPDU *pdu,
148                                        size_t offset,
149                                        const char *fmt,
150                                        va_list ap)
151 {
152     Xen9pfsDev *xen_9pfs = container_of(pdu->s, Xen9pfsDev, state);
153     struct iovec out_sg[2];
154     int num;
155     ssize_t ret;
156 
157     xen_9pfs_out_sg(&xen_9pfs->rings[pdu->tag % xen_9pfs->num_rings],
158                     out_sg, &num, pdu->idx);
159 
160     ret = v9fs_iov_vunmarshal(out_sg, num, offset, 0, fmt, ap);
161     if (ret < 0) {
162         xen_pv_printf(&xen_9pfs->xendev, 0,
163                       "Failed to decode VirtFS request type %d\n", pdu->id);
164         xen_be_set_state(&xen_9pfs->xendev, XenbusStateClosing);
165         xen_9pfs_disconnect(&xen_9pfs->xendev);
166     }
167     return ret;
168 }
169 
170 static void xen_9pfs_init_out_iov_from_pdu(V9fsPDU *pdu,
171                                            struct iovec **piov,
172                                            unsigned int *pniov,
173                                            size_t size)
174 {
175     Xen9pfsDev *xen_9pfs = container_of(pdu->s, Xen9pfsDev, state);
176     Xen9pfsRing *ring = &xen_9pfs->rings[pdu->tag % xen_9pfs->num_rings];
177     int num;
178 
179     g_free(ring->sg);
180 
181     ring->sg = g_new0(struct iovec, 2);
182     xen_9pfs_out_sg(ring, ring->sg, &num, pdu->idx);
183     *piov = ring->sg;
184     *pniov = num;
185 }
186 
187 static void xen_9pfs_init_in_iov_from_pdu(V9fsPDU *pdu,
188                                           struct iovec **piov,
189                                           unsigned int *pniov,
190                                           size_t *size)
191 {
192     Xen9pfsDev *xen_9pfs = container_of(pdu->s, Xen9pfsDev, state);
193     Xen9pfsRing *ring = &xen_9pfs->rings[pdu->tag % xen_9pfs->num_rings];
194     int num;
195     size_t buf_size;
196 
197     g_free(ring->sg);
198 
199     ring->sg = g_new0(struct iovec, 2);
200     xen_9pfs_in_sg(ring, ring->sg, &num, pdu->idx, *size);
201 
202     buf_size = iov_size(ring->sg, num);
203     if (buf_size  < P9_IOHDRSZ) {
204         xen_pv_printf(&xen_9pfs->xendev, 0, "Xen 9pfs request type %d"
205                 "needs %zu bytes, buffer has %zu, less than minimum\n",
206                 pdu->id, *size, buf_size);
207         xen_be_set_state(&xen_9pfs->xendev, XenbusStateClosing);
208         xen_9pfs_disconnect(&xen_9pfs->xendev);
209     }
210     if (buf_size  < *size) {
211         *size = buf_size;
212     }
213 
214     *piov = ring->sg;
215     *pniov = num;
216 }
217 
218 static void xen_9pfs_push_and_notify(V9fsPDU *pdu)
219 {
220     RING_IDX prod;
221     Xen9pfsDev *priv = container_of(pdu->s, Xen9pfsDev, state);
222     Xen9pfsRing *ring = &priv->rings[pdu->tag % priv->num_rings];
223 
224     g_free(ring->sg);
225     ring->sg = NULL;
226 
227     ring->intf->out_cons = ring->out_cons;
228     xen_wmb();
229 
230     prod = ring->intf->in_prod;
231     xen_rmb();
232     ring->intf->in_prod = prod + pdu->size;
233     xen_wmb();
234 
235     ring->inprogress = false;
236     xenevtchn_notify(ring->evtchndev, ring->local_port);
237 
238     qemu_bh_schedule(ring->bh);
239 }
240 
241 static const V9fsTransport xen_9p_transport = {
242     .pdu_vmarshal = xen_9pfs_pdu_vmarshal,
243     .pdu_vunmarshal = xen_9pfs_pdu_vunmarshal,
244     .init_in_iov_from_pdu = xen_9pfs_init_in_iov_from_pdu,
245     .init_out_iov_from_pdu = xen_9pfs_init_out_iov_from_pdu,
246     .push_and_notify = xen_9pfs_push_and_notify,
247 };
248 
249 static int xen_9pfs_init(struct XenLegacyDevice *xendev)
250 {
251     return 0;
252 }
253 
254 static int xen_9pfs_receive(Xen9pfsRing *ring)
255 {
256     P9MsgHeader h;
257     RING_IDX cons, prod, masked_prod, masked_cons, queued;
258     V9fsPDU *pdu;
259 
260     if (ring->inprogress) {
261         return 0;
262     }
263 
264     cons = ring->intf->out_cons;
265     prod = ring->intf->out_prod;
266     xen_rmb();
267 
268     queued = xen_9pfs_queued(prod, cons, XEN_FLEX_RING_SIZE(ring->ring_order));
269     if (queued < sizeof(h)) {
270         return 0;
271     }
272     ring->inprogress = true;
273 
274     masked_prod = xen_9pfs_mask(prod, XEN_FLEX_RING_SIZE(ring->ring_order));
275     masked_cons = xen_9pfs_mask(cons, XEN_FLEX_RING_SIZE(ring->ring_order));
276 
277     xen_9pfs_read_packet((uint8_t *) &h, ring->ring.out, sizeof(h),
278                          masked_prod, &masked_cons,
279                          XEN_FLEX_RING_SIZE(ring->ring_order));
280     if (queued < le32_to_cpu(h.size_le)) {
281         return 0;
282     }
283 
284     /* cannot fail, because we only handle one request per ring at a time */
285     pdu = pdu_alloc(&ring->priv->state);
286     ring->out_size = le32_to_cpu(h.size_le);
287     ring->out_cons = cons + le32_to_cpu(h.size_le);
288 
289     pdu_submit(pdu, &h);
290 
291     return 0;
292 }
293 
294 static void xen_9pfs_bh(void *opaque)
295 {
296     Xen9pfsRing *ring = opaque;
297     xen_9pfs_receive(ring);
298 }
299 
300 static void xen_9pfs_evtchn_event(void *opaque)
301 {
302     Xen9pfsRing *ring = opaque;
303     evtchn_port_t port;
304 
305     port = xenevtchn_pending(ring->evtchndev);
306     xenevtchn_unmask(ring->evtchndev, port);
307 
308     qemu_bh_schedule(ring->bh);
309 }
310 
311 static void xen_9pfs_disconnect(struct XenLegacyDevice *xendev)
312 {
313     Xen9pfsDev *xen_9pdev = container_of(xendev, Xen9pfsDev, xendev);
314     int i;
315 
316     for (i = 0; i < xen_9pdev->num_rings; i++) {
317         if (xen_9pdev->rings[i].evtchndev != NULL) {
318             qemu_set_fd_handler(xenevtchn_fd(xen_9pdev->rings[i].evtchndev),
319                     NULL, NULL, NULL);
320             xenevtchn_unbind(xen_9pdev->rings[i].evtchndev,
321                              xen_9pdev->rings[i].local_port);
322             xen_9pdev->rings[i].evtchndev = NULL;
323         }
324     }
325 }
326 
327 static int xen_9pfs_free(struct XenLegacyDevice *xendev)
328 {
329     Xen9pfsDev *xen_9pdev = container_of(xendev, Xen9pfsDev, xendev);
330     int i;
331 
332     if (xen_9pdev->rings[0].evtchndev != NULL) {
333         xen_9pfs_disconnect(xendev);
334     }
335 
336     for (i = 0; i < xen_9pdev->num_rings; i++) {
337         if (xen_9pdev->rings[i].data != NULL) {
338             xen_be_unmap_grant_refs(&xen_9pdev->xendev,
339                                     xen_9pdev->rings[i].data,
340                                     (1 << xen_9pdev->rings[i].ring_order));
341         }
342         if (xen_9pdev->rings[i].intf != NULL) {
343             xen_be_unmap_grant_refs(&xen_9pdev->xendev,
344                                     xen_9pdev->rings[i].intf,
345                                     1);
346         }
347         if (xen_9pdev->rings[i].bh != NULL) {
348             qemu_bh_delete(xen_9pdev->rings[i].bh);
349         }
350     }
351 
352     g_free(xen_9pdev->id);
353     g_free(xen_9pdev->tag);
354     g_free(xen_9pdev->path);
355     g_free(xen_9pdev->security_model);
356     g_free(xen_9pdev->rings);
357     return 0;
358 }
359 
360 static int xen_9pfs_connect(struct XenLegacyDevice *xendev)
361 {
362     Error *err = NULL;
363     int i;
364     Xen9pfsDev *xen_9pdev = container_of(xendev, Xen9pfsDev, xendev);
365     V9fsState *s = &xen_9pdev->state;
366     QemuOpts *fsdev;
367 
368     if (xenstore_read_fe_int(&xen_9pdev->xendev, "num-rings",
369                              &xen_9pdev->num_rings) == -1 ||
370         xen_9pdev->num_rings > MAX_RINGS || xen_9pdev->num_rings < 1) {
371         return -1;
372     }
373 
374     xen_9pdev->rings = g_new0(Xen9pfsRing, xen_9pdev->num_rings);
375     for (i = 0; i < xen_9pdev->num_rings; i++) {
376         char *str;
377         int ring_order;
378 
379         xen_9pdev->rings[i].priv = xen_9pdev;
380         xen_9pdev->rings[i].evtchn = -1;
381         xen_9pdev->rings[i].local_port = -1;
382 
383         str = g_strdup_printf("ring-ref%u", i);
384         if (xenstore_read_fe_int(&xen_9pdev->xendev, str,
385                                  &xen_9pdev->rings[i].ref) == -1) {
386             g_free(str);
387             goto out;
388         }
389         g_free(str);
390         str = g_strdup_printf("event-channel-%u", i);
391         if (xenstore_read_fe_int(&xen_9pdev->xendev, str,
392                                  &xen_9pdev->rings[i].evtchn) == -1) {
393             g_free(str);
394             goto out;
395         }
396         g_free(str);
397 
398         xen_9pdev->rings[i].intf =
399             xen_be_map_grant_ref(&xen_9pdev->xendev,
400                                  xen_9pdev->rings[i].ref,
401                                  PROT_READ | PROT_WRITE);
402         if (!xen_9pdev->rings[i].intf) {
403             goto out;
404         }
405         ring_order = xen_9pdev->rings[i].intf->ring_order;
406         if (ring_order > MAX_RING_ORDER) {
407             goto out;
408         }
409         xen_9pdev->rings[i].ring_order = ring_order;
410         xen_9pdev->rings[i].data =
411             xen_be_map_grant_refs(&xen_9pdev->xendev,
412                                   xen_9pdev->rings[i].intf->ref,
413                                   (1 << ring_order),
414                                   PROT_READ | PROT_WRITE);
415         if (!xen_9pdev->rings[i].data) {
416             goto out;
417         }
418         xen_9pdev->rings[i].ring.in = xen_9pdev->rings[i].data;
419         xen_9pdev->rings[i].ring.out = xen_9pdev->rings[i].data +
420                                        XEN_FLEX_RING_SIZE(ring_order);
421 
422         xen_9pdev->rings[i].bh = qemu_bh_new(xen_9pfs_bh, &xen_9pdev->rings[i]);
423         xen_9pdev->rings[i].out_cons = 0;
424         xen_9pdev->rings[i].out_size = 0;
425         xen_9pdev->rings[i].inprogress = false;
426 
427 
428         xen_9pdev->rings[i].evtchndev = xenevtchn_open(NULL, 0);
429         if (xen_9pdev->rings[i].evtchndev == NULL) {
430             goto out;
431         }
432         qemu_set_cloexec(xenevtchn_fd(xen_9pdev->rings[i].evtchndev));
433         xen_9pdev->rings[i].local_port = xenevtchn_bind_interdomain
434                                             (xen_9pdev->rings[i].evtchndev,
435                                              xendev->dom,
436                                              xen_9pdev->rings[i].evtchn);
437         if (xen_9pdev->rings[i].local_port == -1) {
438             xen_pv_printf(xendev, 0,
439                           "xenevtchn_bind_interdomain failed port=%d\n",
440                           xen_9pdev->rings[i].evtchn);
441             goto out;
442         }
443         xen_pv_printf(xendev, 2, "bind evtchn port %d\n", xendev->local_port);
444         qemu_set_fd_handler(xenevtchn_fd(xen_9pdev->rings[i].evtchndev),
445                 xen_9pfs_evtchn_event, NULL, &xen_9pdev->rings[i]);
446     }
447 
448     xen_9pdev->security_model = xenstore_read_be_str(xendev, "security_model");
449     xen_9pdev->path = xenstore_read_be_str(xendev, "path");
450     xen_9pdev->id = s->fsconf.fsdev_id =
451         g_strdup_printf("xen9p%d", xendev->dev);
452     xen_9pdev->tag = s->fsconf.tag = xenstore_read_fe_str(xendev, "tag");
453     fsdev = qemu_opts_create(qemu_find_opts("fsdev"),
454             s->fsconf.tag,
455             1, NULL);
456     qemu_opt_set(fsdev, "fsdriver", "local", NULL);
457     qemu_opt_set(fsdev, "path", xen_9pdev->path, NULL);
458     qemu_opt_set(fsdev, "security_model", xen_9pdev->security_model, NULL);
459     qemu_opts_set_id(fsdev, s->fsconf.fsdev_id);
460     qemu_fsdev_add(fsdev, &err);
461     if (err) {
462         error_report_err(err);
463     }
464     v9fs_device_realize_common(s, &xen_9p_transport, NULL);
465 
466     return 0;
467 
468 out:
469     xen_9pfs_free(xendev);
470     return -1;
471 }
472 
473 static void xen_9pfs_alloc(struct XenLegacyDevice *xendev)
474 {
475     xenstore_write_be_str(xendev, "versions", VERSIONS);
476     xenstore_write_be_int(xendev, "max-rings", MAX_RINGS);
477     xenstore_write_be_int(xendev, "max-ring-page-order", MAX_RING_ORDER);
478 }
479 
480 struct XenDevOps xen_9pfs_ops = {
481     .size       = sizeof(Xen9pfsDev),
482     .flags      = DEVOPS_FLAG_NEED_GNTDEV,
483     .alloc      = xen_9pfs_alloc,
484     .init       = xen_9pfs_init,
485     .initialise = xen_9pfs_connect,
486     .disconnect = xen_9pfs_disconnect,
487     .free       = xen_9pfs_free,
488 };
489