xref: /openbmc/qemu/hw/9pfs/xen-9p-backend.c (revision 59a3a1c0) 
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  < size) {
204         xen_pv_printf(&xen_9pfs->xendev, 0, "Xen 9pfs request type %d"
205                 "needs %zu bytes, buffer has %zu\n", pdu->id, size,
206                 buf_size);
207         xen_be_set_state(&xen_9pfs->xendev, XenbusStateClosing);
208         xen_9pfs_disconnect(&xen_9pfs->xendev);
209     }
210 
211     *piov = ring->sg;
212     *pniov = num;
213 }
214 
215 static void xen_9pfs_push_and_notify(V9fsPDU *pdu)
216 {
217     RING_IDX prod;
218     Xen9pfsDev *priv = container_of(pdu->s, Xen9pfsDev, state);
219     Xen9pfsRing *ring = &priv->rings[pdu->tag % priv->num_rings];
220 
221     g_free(ring->sg);
222     ring->sg = NULL;
223 
224     ring->intf->out_cons = ring->out_cons;
225     xen_wmb();
226 
227     prod = ring->intf->in_prod;
228     xen_rmb();
229     ring->intf->in_prod = prod + pdu->size;
230     xen_wmb();
231 
232     ring->inprogress = false;
233     xenevtchn_notify(ring->evtchndev, ring->local_port);
234 
235     qemu_bh_schedule(ring->bh);
236 }
237 
238 static const V9fsTransport xen_9p_transport = {
239     .pdu_vmarshal = xen_9pfs_pdu_vmarshal,
240     .pdu_vunmarshal = xen_9pfs_pdu_vunmarshal,
241     .init_in_iov_from_pdu = xen_9pfs_init_in_iov_from_pdu,
242     .init_out_iov_from_pdu = xen_9pfs_init_out_iov_from_pdu,
243     .push_and_notify = xen_9pfs_push_and_notify,
244 };
245 
246 static int xen_9pfs_init(struct XenLegacyDevice *xendev)
247 {
248     return 0;
249 }
250 
251 static int xen_9pfs_receive(Xen9pfsRing *ring)
252 {
253     P9MsgHeader h;
254     RING_IDX cons, prod, masked_prod, masked_cons, queued;
255     V9fsPDU *pdu;
256 
257     if (ring->inprogress) {
258         return 0;
259     }
260 
261     cons = ring->intf->out_cons;
262     prod = ring->intf->out_prod;
263     xen_rmb();
264 
265     queued = xen_9pfs_queued(prod, cons, XEN_FLEX_RING_SIZE(ring->ring_order));
266     if (queued < sizeof(h)) {
267         return 0;
268     }
269     ring->inprogress = true;
270 
271     masked_prod = xen_9pfs_mask(prod, XEN_FLEX_RING_SIZE(ring->ring_order));
272     masked_cons = xen_9pfs_mask(cons, XEN_FLEX_RING_SIZE(ring->ring_order));
273 
274     xen_9pfs_read_packet((uint8_t *) &h, ring->ring.out, sizeof(h),
275                          masked_prod, &masked_cons,
276                          XEN_FLEX_RING_SIZE(ring->ring_order));
277     if (queued < le32_to_cpu(h.size_le)) {
278         return 0;
279     }
280 
281     /* cannot fail, because we only handle one request per ring at a time */
282     pdu = pdu_alloc(&ring->priv->state);
283     ring->out_size = le32_to_cpu(h.size_le);
284     ring->out_cons = cons + le32_to_cpu(h.size_le);
285 
286     pdu_submit(pdu, &h);
287 
288     return 0;
289 }
290 
291 static void xen_9pfs_bh(void *opaque)
292 {
293     Xen9pfsRing *ring = opaque;
294     xen_9pfs_receive(ring);
295 }
296 
297 static void xen_9pfs_evtchn_event(void *opaque)
298 {
299     Xen9pfsRing *ring = opaque;
300     evtchn_port_t port;
301 
302     port = xenevtchn_pending(ring->evtchndev);
303     xenevtchn_unmask(ring->evtchndev, port);
304 
305     qemu_bh_schedule(ring->bh);
306 }
307 
308 static void xen_9pfs_disconnect(struct XenLegacyDevice *xendev)
309 {
310     Xen9pfsDev *xen_9pdev = container_of(xendev, Xen9pfsDev, xendev);
311     int i;
312 
313     for (i = 0; i < xen_9pdev->num_rings; i++) {
314         if (xen_9pdev->rings[i].evtchndev != NULL) {
315             qemu_set_fd_handler(xenevtchn_fd(xen_9pdev->rings[i].evtchndev),
316                     NULL, NULL, NULL);
317             xenevtchn_unbind(xen_9pdev->rings[i].evtchndev,
318                              xen_9pdev->rings[i].local_port);
319             xen_9pdev->rings[i].evtchndev = NULL;
320         }
321     }
322 }
323 
324 static int xen_9pfs_free(struct XenLegacyDevice *xendev)
325 {
326     Xen9pfsDev *xen_9pdev = container_of(xendev, Xen9pfsDev, xendev);
327     int i;
328 
329     if (xen_9pdev->rings[0].evtchndev != NULL) {
330         xen_9pfs_disconnect(xendev);
331     }
332 
333     for (i = 0; i < xen_9pdev->num_rings; i++) {
334         if (xen_9pdev->rings[i].data != NULL) {
335             xen_be_unmap_grant_refs(&xen_9pdev->xendev,
336                                     xen_9pdev->rings[i].data,
337                                     (1 << xen_9pdev->rings[i].ring_order));
338         }
339         if (xen_9pdev->rings[i].intf != NULL) {
340             xen_be_unmap_grant_refs(&xen_9pdev->xendev,
341                                     xen_9pdev->rings[i].intf,
342                                     1);
343         }
344         if (xen_9pdev->rings[i].bh != NULL) {
345             qemu_bh_delete(xen_9pdev->rings[i].bh);
346         }
347     }
348 
349     g_free(xen_9pdev->id);
350     g_free(xen_9pdev->tag);
351     g_free(xen_9pdev->path);
352     g_free(xen_9pdev->security_model);
353     g_free(xen_9pdev->rings);
354     return 0;
355 }
356 
357 static int xen_9pfs_connect(struct XenLegacyDevice *xendev)
358 {
359     Error *err = NULL;
360     int i;
361     Xen9pfsDev *xen_9pdev = container_of(xendev, Xen9pfsDev, xendev);
362     V9fsState *s = &xen_9pdev->state;
363     QemuOpts *fsdev;
364 
365     if (xenstore_read_fe_int(&xen_9pdev->xendev, "num-rings",
366                              &xen_9pdev->num_rings) == -1 ||
367         xen_9pdev->num_rings > MAX_RINGS || xen_9pdev->num_rings < 1) {
368         return -1;
369     }
370 
371     xen_9pdev->rings = g_new0(Xen9pfsRing, xen_9pdev->num_rings);
372     for (i = 0; i < xen_9pdev->num_rings; i++) {
373         char *str;
374         int ring_order;
375 
376         xen_9pdev->rings[i].priv = xen_9pdev;
377         xen_9pdev->rings[i].evtchn = -1;
378         xen_9pdev->rings[i].local_port = -1;
379 
380         str = g_strdup_printf("ring-ref%u", i);
381         if (xenstore_read_fe_int(&xen_9pdev->xendev, str,
382                                  &xen_9pdev->rings[i].ref) == -1) {
383             g_free(str);
384             goto out;
385         }
386         g_free(str);
387         str = g_strdup_printf("event-channel-%u", i);
388         if (xenstore_read_fe_int(&xen_9pdev->xendev, str,
389                                  &xen_9pdev->rings[i].evtchn) == -1) {
390             g_free(str);
391             goto out;
392         }
393         g_free(str);
394 
395         xen_9pdev->rings[i].intf =
396             xen_be_map_grant_ref(&xen_9pdev->xendev,
397                                  xen_9pdev->rings[i].ref,
398                                  PROT_READ | PROT_WRITE);
399         if (!xen_9pdev->rings[i].intf) {
400             goto out;
401         }
402         ring_order = xen_9pdev->rings[i].intf->ring_order;
403         if (ring_order > MAX_RING_ORDER) {
404             goto out;
405         }
406         xen_9pdev->rings[i].ring_order = ring_order;
407         xen_9pdev->rings[i].data =
408             xen_be_map_grant_refs(&xen_9pdev->xendev,
409                                   xen_9pdev->rings[i].intf->ref,
410                                   (1 << ring_order),
411                                   PROT_READ | PROT_WRITE);
412         if (!xen_9pdev->rings[i].data) {
413             goto out;
414         }
415         xen_9pdev->rings[i].ring.in = xen_9pdev->rings[i].data;
416         xen_9pdev->rings[i].ring.out = xen_9pdev->rings[i].data +
417                                        XEN_FLEX_RING_SIZE(ring_order);
418 
419         xen_9pdev->rings[i].bh = qemu_bh_new(xen_9pfs_bh, &xen_9pdev->rings[i]);
420         xen_9pdev->rings[i].out_cons = 0;
421         xen_9pdev->rings[i].out_size = 0;
422         xen_9pdev->rings[i].inprogress = false;
423 
424 
425         xen_9pdev->rings[i].evtchndev = xenevtchn_open(NULL, 0);
426         if (xen_9pdev->rings[i].evtchndev == NULL) {
427             goto out;
428         }
429         qemu_set_cloexec(xenevtchn_fd(xen_9pdev->rings[i].evtchndev));
430         xen_9pdev->rings[i].local_port = xenevtchn_bind_interdomain
431                                             (xen_9pdev->rings[i].evtchndev,
432                                              xendev->dom,
433                                              xen_9pdev->rings[i].evtchn);
434         if (xen_9pdev->rings[i].local_port == -1) {
435             xen_pv_printf(xendev, 0,
436                           "xenevtchn_bind_interdomain failed port=%d\n",
437                           xen_9pdev->rings[i].evtchn);
438             goto out;
439         }
440         xen_pv_printf(xendev, 2, "bind evtchn port %d\n", xendev->local_port);
441         qemu_set_fd_handler(xenevtchn_fd(xen_9pdev->rings[i].evtchndev),
442                 xen_9pfs_evtchn_event, NULL, &xen_9pdev->rings[i]);
443     }
444 
445     xen_9pdev->security_model = xenstore_read_be_str(xendev, "security_model");
446     xen_9pdev->path = xenstore_read_be_str(xendev, "path");
447     xen_9pdev->id = s->fsconf.fsdev_id =
448         g_strdup_printf("xen9p%d", xendev->dev);
449     xen_9pdev->tag = s->fsconf.tag = xenstore_read_fe_str(xendev, "tag");
450     fsdev = qemu_opts_create(qemu_find_opts("fsdev"),
451             s->fsconf.tag,
452             1, NULL);
453     qemu_opt_set(fsdev, "fsdriver", "local", NULL);
454     qemu_opt_set(fsdev, "path", xen_9pdev->path, NULL);
455     qemu_opt_set(fsdev, "security_model", xen_9pdev->security_model, NULL);
456     qemu_opts_set_id(fsdev, s->fsconf.fsdev_id);
457     qemu_fsdev_add(fsdev, &err);
458     if (err) {
459         error_report_err(err);
460     }
461     v9fs_device_realize_common(s, &xen_9p_transport, NULL);
462 
463     return 0;
464 
465 out:
466     xen_9pfs_free(xendev);
467     return -1;
468 }
469 
470 static void xen_9pfs_alloc(struct XenLegacyDevice *xendev)
471 {
472     xenstore_write_be_str(xendev, "versions", VERSIONS);
473     xenstore_write_be_int(xendev, "max-rings", MAX_RINGS);
474     xenstore_write_be_int(xendev, "max-ring-page-order", MAX_RING_ORDER);
475 }
476 
477 struct XenDevOps xen_9pfs_ops = {
478     .size       = sizeof(Xen9pfsDev),
479     .flags      = DEVOPS_FLAG_NEED_GNTDEV,
480     .alloc      = xen_9pfs_alloc,
481     .init       = xen_9pfs_init,
482     .initialise = xen_9pfs_connect,
483     .disconnect = xen_9pfs_disconnect,
484     .free       = xen_9pfs_free,
485 };
486