xref: /openbmc/qemu/hw/9pfs/xen-9p-backend.c (revision 56e2cd24) 
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/hw.h"
14 #include "hw/9pfs/9p.h"
15 #include "hw/xen/xen_backend.h"
16 #include "hw/9pfs/xen-9pfs.h"
17 #include "qemu/config-file.h"
18 #include "fsdev/qemu-fsdev.h"
19 
20 #define VERSIONS "1"
21 #define MAX_RINGS 8
22 #define MAX_RING_ORDER 8
23 
24 typedef struct Xen9pfsRing {
25     struct Xen9pfsDev *priv;
26 
27     int ref;
28     xenevtchn_handle   *evtchndev;
29     int evtchn;
30     int local_port;
31     int ring_order;
32     struct xen_9pfs_data_intf *intf;
33     unsigned char *data;
34     struct xen_9pfs_data ring;
35 
36     struct iovec *sg;
37     QEMUBH *bh;
38 
39     /* local copies, so that we can read/write PDU data directly from
40      * the ring */
41     RING_IDX out_cons, out_size, in_cons;
42     bool inprogress;
43 } Xen9pfsRing;
44 
45 typedef struct Xen9pfsDev {
46     struct XenDevice xendev;  /* must be first */
47     V9fsState state;
48     char *path;
49     char *security_model;
50     char *tag;
51     char *id;
52 
53     int num_rings;
54     Xen9pfsRing *rings;
55 } Xen9pfsDev;
56 
57 static void xen_9pfs_in_sg(Xen9pfsRing *ring,
58                            struct iovec *in_sg,
59                            int *num,
60                            uint32_t idx,
61                            uint32_t size)
62 {
63     RING_IDX cons, prod, masked_prod, masked_cons;
64 
65     cons = ring->intf->in_cons;
66     prod = ring->intf->in_prod;
67     xen_rmb();
68     masked_prod = xen_9pfs_mask(prod, XEN_FLEX_RING_SIZE(ring->ring_order));
69     masked_cons = xen_9pfs_mask(cons, XEN_FLEX_RING_SIZE(ring->ring_order));
70 
71     if (masked_prod < masked_cons) {
72         in_sg[0].iov_base = ring->ring.in + masked_prod;
73         in_sg[0].iov_len = masked_cons - masked_prod;
74         *num = 1;
75     } else {
76         in_sg[0].iov_base = ring->ring.in + masked_prod;
77         in_sg[0].iov_len = XEN_FLEX_RING_SIZE(ring->ring_order) - masked_prod;
78         in_sg[1].iov_base = ring->ring.in;
79         in_sg[1].iov_len = masked_cons;
80         *num = 2;
81     }
82 }
83 
84 static void xen_9pfs_out_sg(Xen9pfsRing *ring,
85                             struct iovec *out_sg,
86                             int *num,
87                             uint32_t idx)
88 {
89     RING_IDX cons, prod, masked_prod, masked_cons;
90 
91     cons = ring->intf->out_cons;
92     prod = ring->intf->out_prod;
93     xen_rmb();
94     masked_prod = xen_9pfs_mask(prod, XEN_FLEX_RING_SIZE(ring->ring_order));
95     masked_cons = xen_9pfs_mask(cons, XEN_FLEX_RING_SIZE(ring->ring_order));
96 
97     if (masked_cons < masked_prod) {
98         out_sg[0].iov_base = ring->ring.out + masked_cons;
99         out_sg[0].iov_len = ring->out_size;
100         *num = 1;
101     } else {
102         if (ring->out_size >
103             (XEN_FLEX_RING_SIZE(ring->ring_order) - masked_cons)) {
104             out_sg[0].iov_base = ring->ring.out + masked_cons;
105             out_sg[0].iov_len = XEN_FLEX_RING_SIZE(ring->ring_order) -
106                                 masked_cons;
107             out_sg[1].iov_base = ring->ring.out;
108             out_sg[1].iov_len = ring->out_size -
109                                 (XEN_FLEX_RING_SIZE(ring->ring_order) -
110                                  masked_cons);
111             *num = 2;
112         } else {
113             out_sg[0].iov_base = ring->ring.out + masked_cons;
114             out_sg[0].iov_len = ring->out_size;
115             *num = 1;
116         }
117     }
118 }
119 
120 static ssize_t xen_9pfs_pdu_vmarshal(V9fsPDU *pdu,
121                                      size_t offset,
122                                      const char *fmt,
123                                      va_list ap)
124 {
125     Xen9pfsDev *xen_9pfs = container_of(pdu->s, Xen9pfsDev, state);
126     struct iovec in_sg[2];
127     int num;
128 
129     xen_9pfs_in_sg(&xen_9pfs->rings[pdu->tag % xen_9pfs->num_rings],
130                    in_sg, &num, pdu->idx, ROUND_UP(offset + 128, 512));
131     return v9fs_iov_vmarshal(in_sg, num, offset, 0, fmt, ap);
132 }
133 
134 static ssize_t xen_9pfs_pdu_vunmarshal(V9fsPDU *pdu,
135                                        size_t offset,
136                                        const char *fmt,
137                                        va_list ap)
138 {
139     Xen9pfsDev *xen_9pfs = container_of(pdu->s, Xen9pfsDev, state);
140     struct iovec out_sg[2];
141     int num;
142 
143     xen_9pfs_out_sg(&xen_9pfs->rings[pdu->tag % xen_9pfs->num_rings],
144                     out_sg, &num, pdu->idx);
145     return v9fs_iov_vunmarshal(out_sg, num, offset, 0, fmt, ap);
146 }
147 
148 static void xen_9pfs_init_out_iov_from_pdu(V9fsPDU *pdu,
149                                            struct iovec **piov,
150                                            unsigned int *pniov)
151 {
152     Xen9pfsDev *xen_9pfs = container_of(pdu->s, Xen9pfsDev, state);
153     Xen9pfsRing *ring = &xen_9pfs->rings[pdu->tag % xen_9pfs->num_rings];
154     int num;
155 
156     g_free(ring->sg);
157 
158     ring->sg = g_malloc0(sizeof(*ring->sg) * 2);
159     xen_9pfs_out_sg(ring, ring->sg, &num, pdu->idx);
160     *piov = ring->sg;
161     *pniov = num;
162 }
163 
164 static void xen_9pfs_init_in_iov_from_pdu(V9fsPDU *pdu,
165                                           struct iovec **piov,
166                                           unsigned int *pniov,
167                                           size_t size)
168 {
169     Xen9pfsDev *xen_9pfs = container_of(pdu->s, Xen9pfsDev, state);
170     Xen9pfsRing *ring = &xen_9pfs->rings[pdu->tag % xen_9pfs->num_rings];
171     int num;
172 
173     g_free(ring->sg);
174 
175     ring->sg = g_malloc0(sizeof(*ring->sg) * 2);
176     xen_9pfs_in_sg(ring, ring->sg, &num, pdu->idx, size);
177     *piov = ring->sg;
178     *pniov = num;
179 }
180 
181 static void xen_9pfs_push_and_notify(V9fsPDU *pdu)
182 {
183     RING_IDX prod;
184     Xen9pfsDev *priv = container_of(pdu->s, Xen9pfsDev, state);
185     Xen9pfsRing *ring = &priv->rings[pdu->tag % priv->num_rings];
186 
187     g_free(ring->sg);
188     ring->sg = NULL;
189 
190     ring->intf->out_cons = ring->out_cons;
191     xen_wmb();
192 
193     prod = ring->intf->in_prod;
194     xen_rmb();
195     ring->intf->in_prod = prod + pdu->size;
196     xen_wmb();
197 
198     ring->inprogress = false;
199     xenevtchn_notify(ring->evtchndev, ring->local_port);
200 
201     qemu_bh_schedule(ring->bh);
202 }
203 
204 static const struct V9fsTransport xen_9p_transport = {
205     .pdu_vmarshal = xen_9pfs_pdu_vmarshal,
206     .pdu_vunmarshal = xen_9pfs_pdu_vunmarshal,
207     .init_in_iov_from_pdu = xen_9pfs_init_in_iov_from_pdu,
208     .init_out_iov_from_pdu = xen_9pfs_init_out_iov_from_pdu,
209     .push_and_notify = xen_9pfs_push_and_notify,
210 };
211 
212 static int xen_9pfs_init(struct XenDevice *xendev)
213 {
214     return 0;
215 }
216 
217 static int xen_9pfs_receive(Xen9pfsRing *ring)
218 {
219     P9MsgHeader h;
220     RING_IDX cons, prod, masked_prod, masked_cons;
221     V9fsPDU *pdu;
222 
223     if (ring->inprogress) {
224         return 0;
225     }
226 
227     cons = ring->intf->out_cons;
228     prod = ring->intf->out_prod;
229     xen_rmb();
230 
231     if (xen_9pfs_queued(prod, cons, XEN_FLEX_RING_SIZE(ring->ring_order)) <
232         sizeof(h)) {
233         return 0;
234     }
235     ring->inprogress = true;
236 
237     masked_prod = xen_9pfs_mask(prod, XEN_FLEX_RING_SIZE(ring->ring_order));
238     masked_cons = xen_9pfs_mask(cons, XEN_FLEX_RING_SIZE(ring->ring_order));
239 
240     xen_9pfs_read_packet((uint8_t *) &h, ring->ring.out, sizeof(h),
241                          masked_prod, &masked_cons,
242                          XEN_FLEX_RING_SIZE(ring->ring_order));
243 
244     /* cannot fail, because we only handle one request per ring at a time */
245     pdu = pdu_alloc(&ring->priv->state);
246     pdu->size = le32_to_cpu(h.size_le);
247     pdu->id = h.id;
248     pdu->tag = le32_to_cpu(h.tag_le);
249     ring->out_size = le32_to_cpu(h.size_le);
250     ring->out_cons = cons + le32_to_cpu(h.size_le);
251 
252     qemu_co_queue_init(&pdu->complete);
253     pdu_submit(pdu);
254 
255     return 0;
256 }
257 
258 static void xen_9pfs_bh(void *opaque)
259 {
260     Xen9pfsRing *ring = opaque;
261     xen_9pfs_receive(ring);
262 }
263 
264 static void xen_9pfs_evtchn_event(void *opaque)
265 {
266     Xen9pfsRing *ring = opaque;
267     evtchn_port_t port;
268 
269     port = xenevtchn_pending(ring->evtchndev);
270     xenevtchn_unmask(ring->evtchndev, port);
271 
272     qemu_bh_schedule(ring->bh);
273 }
274 
275 static int xen_9pfs_free(struct XenDevice *xendev)
276 {
277     int i;
278     Xen9pfsDev *xen_9pdev = container_of(xendev, Xen9pfsDev, xendev);
279 
280     g_free(xen_9pdev->id);
281     g_free(xen_9pdev->tag);
282     g_free(xen_9pdev->path);
283     g_free(xen_9pdev->security_model);
284 
285     for (i = 0; i < xen_9pdev->num_rings; i++) {
286         if (xen_9pdev->rings[i].data != NULL) {
287             xengnttab_unmap(xen_9pdev->xendev.gnttabdev,
288                     xen_9pdev->rings[i].data,
289                     (1 << xen_9pdev->rings[i].ring_order));
290         }
291         if (xen_9pdev->rings[i].intf != NULL) {
292             xengnttab_unmap(xen_9pdev->xendev.gnttabdev,
293                     xen_9pdev->rings[i].intf,
294                     1);
295         }
296         if (xen_9pdev->rings[i].evtchndev > 0) {
297             qemu_set_fd_handler(xenevtchn_fd(xen_9pdev->rings[i].evtchndev),
298                     NULL, NULL, NULL);
299             xenevtchn_unbind(xen_9pdev->rings[i].evtchndev,
300                              xen_9pdev->rings[i].local_port);
301         }
302         if (xen_9pdev->rings[i].bh != NULL) {
303             qemu_bh_delete(xen_9pdev->rings[i].bh);
304         }
305     }
306     g_free(xen_9pdev->rings);
307     return 0;
308 }
309 
310 static int xen_9pfs_connect(struct XenDevice *xendev)
311 {
312     int i;
313     Xen9pfsDev *xen_9pdev = container_of(xendev, Xen9pfsDev, xendev);
314     V9fsState *s = &xen_9pdev->state;
315     QemuOpts *fsdev;
316 
317     if (xenstore_read_fe_int(&xen_9pdev->xendev, "num-rings",
318                              &xen_9pdev->num_rings) == -1 ||
319         xen_9pdev->num_rings > MAX_RINGS || xen_9pdev->num_rings < 1) {
320         return -1;
321     }
322 
323     xen_9pdev->rings = g_malloc0(xen_9pdev->num_rings * sizeof(Xen9pfsRing));
324     for (i = 0; i < xen_9pdev->num_rings; i++) {
325         char *str;
326         int ring_order;
327 
328         xen_9pdev->rings[i].priv = xen_9pdev;
329         xen_9pdev->rings[i].evtchn = -1;
330         xen_9pdev->rings[i].local_port = -1;
331 
332         str = g_strdup_printf("ring-ref%u", i);
333         if (xenstore_read_fe_int(&xen_9pdev->xendev, str,
334                                  &xen_9pdev->rings[i].ref) == -1) {
335             goto out;
336         }
337         g_free(str);
338         str = g_strdup_printf("event-channel-%u", i);
339         if (xenstore_read_fe_int(&xen_9pdev->xendev, str,
340                                  &xen_9pdev->rings[i].evtchn) == -1) {
341             goto out;
342         }
343         g_free(str);
344 
345         xen_9pdev->rings[i].intf =  xengnttab_map_grant_ref(
346                 xen_9pdev->xendev.gnttabdev,
347                 xen_9pdev->xendev.dom,
348                 xen_9pdev->rings[i].ref,
349                 PROT_READ | PROT_WRITE);
350         if (!xen_9pdev->rings[i].intf) {
351             goto out;
352         }
353         ring_order = xen_9pdev->rings[i].intf->ring_order;
354         if (ring_order > MAX_RING_ORDER) {
355             goto out;
356         }
357         xen_9pdev->rings[i].ring_order = ring_order;
358         xen_9pdev->rings[i].data = xengnttab_map_domain_grant_refs(
359                 xen_9pdev->xendev.gnttabdev,
360                 (1 << ring_order),
361                 xen_9pdev->xendev.dom,
362                 xen_9pdev->rings[i].intf->ref,
363                 PROT_READ | PROT_WRITE);
364         if (!xen_9pdev->rings[i].data) {
365             goto out;
366         }
367         xen_9pdev->rings[i].ring.in = xen_9pdev->rings[i].data;
368         xen_9pdev->rings[i].ring.out = xen_9pdev->rings[i].data +
369                                        XEN_FLEX_RING_SIZE(ring_order);
370 
371         xen_9pdev->rings[i].bh = qemu_bh_new(xen_9pfs_bh, &xen_9pdev->rings[i]);
372         xen_9pdev->rings[i].out_cons = 0;
373         xen_9pdev->rings[i].out_size = 0;
374         xen_9pdev->rings[i].inprogress = false;
375 
376 
377         xen_9pdev->rings[i].evtchndev = xenevtchn_open(NULL, 0);
378         if (xen_9pdev->rings[i].evtchndev == NULL) {
379             goto out;
380         }
381         fcntl(xenevtchn_fd(xen_9pdev->rings[i].evtchndev), F_SETFD, FD_CLOEXEC);
382         xen_9pdev->rings[i].local_port = xenevtchn_bind_interdomain
383                                             (xen_9pdev->rings[i].evtchndev,
384                                              xendev->dom,
385                                              xen_9pdev->rings[i].evtchn);
386         if (xen_9pdev->rings[i].local_port == -1) {
387             xen_pv_printf(xendev, 0,
388                           "xenevtchn_bind_interdomain failed port=%d\n",
389                           xen_9pdev->rings[i].evtchn);
390             goto out;
391         }
392         xen_pv_printf(xendev, 2, "bind evtchn port %d\n", xendev->local_port);
393         qemu_set_fd_handler(xenevtchn_fd(xen_9pdev->rings[i].evtchndev),
394                 xen_9pfs_evtchn_event, NULL, &xen_9pdev->rings[i]);
395     }
396 
397     xen_9pdev->security_model = xenstore_read_be_str(xendev, "security_model");
398     xen_9pdev->path = xenstore_read_be_str(xendev, "path");
399     xen_9pdev->id = s->fsconf.fsdev_id =
400         g_strdup_printf("xen9p%d", xendev->dev);
401     xen_9pdev->tag = s->fsconf.tag = xenstore_read_fe_str(xendev, "tag");
402     v9fs_register_transport(s, &xen_9p_transport);
403     fsdev = qemu_opts_create(qemu_find_opts("fsdev"),
404             s->fsconf.tag,
405             1, NULL);
406     qemu_opt_set(fsdev, "fsdriver", "local", NULL);
407     qemu_opt_set(fsdev, "path", xen_9pdev->path, NULL);
408     qemu_opt_set(fsdev, "security_model", xen_9pdev->security_model, NULL);
409     qemu_opts_set_id(fsdev, s->fsconf.fsdev_id);
410     qemu_fsdev_add(fsdev);
411     v9fs_device_realize_common(s, NULL);
412 
413     return 0;
414 
415 out:
416     xen_9pfs_free(xendev);
417     return -1;
418 }
419 
420 static void xen_9pfs_alloc(struct XenDevice *xendev)
421 {
422     xenstore_write_be_str(xendev, "versions", VERSIONS);
423     xenstore_write_be_int(xendev, "max-rings", MAX_RINGS);
424     xenstore_write_be_int(xendev, "max-ring-page-order", MAX_RING_ORDER);
425 }
426 
427 static void xen_9pfs_disconnect(struct XenDevice *xendev)
428 {
429     /* Dynamic hotplug of PV filesystems at runtime is not supported. */
430 }
431 
432 struct XenDevOps xen_9pfs_ops = {
433     .size       = sizeof(Xen9pfsDev),
434     .flags      = DEVOPS_FLAG_NEED_GNTDEV,
435     .alloc      = xen_9pfs_alloc,
436     .init       = xen_9pfs_init,
437     .initialise = xen_9pfs_connect,
438     .disconnect = xen_9pfs_disconnect,
439     .free       = xen_9pfs_free,
440 };
441