xref: /openbmc/qemu/hw/9pfs/xen-9p-backend.c (revision ac06724a715864942e2b5e28f92d5d5421f0a0b0) 
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     ring->out_size = le32_to_cpu(h.size_le);
247     ring->out_cons = cons + le32_to_cpu(h.size_le);
248 
249     pdu_submit(pdu, &h);
250 
251     return 0;
252 }
253 
254 static void xen_9pfs_bh(void *opaque)
255 {
256     Xen9pfsRing *ring = opaque;
257     xen_9pfs_receive(ring);
258 }
259 
260 static void xen_9pfs_evtchn_event(void *opaque)
261 {
262     Xen9pfsRing *ring = opaque;
263     evtchn_port_t port;
264 
265     port = xenevtchn_pending(ring->evtchndev);
266     xenevtchn_unmask(ring->evtchndev, port);
267 
268     qemu_bh_schedule(ring->bh);
269 }
270 
271 static int xen_9pfs_free(struct XenDevice *xendev)
272 {
273     int i;
274     Xen9pfsDev *xen_9pdev = container_of(xendev, Xen9pfsDev, xendev);
275 
276     g_free(xen_9pdev->id);
277     g_free(xen_9pdev->tag);
278     g_free(xen_9pdev->path);
279     g_free(xen_9pdev->security_model);
280 
281     for (i = 0; i < xen_9pdev->num_rings; i++) {
282         if (xen_9pdev->rings[i].data != NULL) {
283             xengnttab_unmap(xen_9pdev->xendev.gnttabdev,
284                     xen_9pdev->rings[i].data,
285                     (1 << xen_9pdev->rings[i].ring_order));
286         }
287         if (xen_9pdev->rings[i].intf != NULL) {
288             xengnttab_unmap(xen_9pdev->xendev.gnttabdev,
289                     xen_9pdev->rings[i].intf,
290                     1);
291         }
292         if (xen_9pdev->rings[i].evtchndev > 0) {
293             qemu_set_fd_handler(xenevtchn_fd(xen_9pdev->rings[i].evtchndev),
294                     NULL, NULL, NULL);
295             xenevtchn_unbind(xen_9pdev->rings[i].evtchndev,
296                              xen_9pdev->rings[i].local_port);
297         }
298         if (xen_9pdev->rings[i].bh != NULL) {
299             qemu_bh_delete(xen_9pdev->rings[i].bh);
300         }
301     }
302     g_free(xen_9pdev->rings);
303     return 0;
304 }
305 
306 static int xen_9pfs_connect(struct XenDevice *xendev)
307 {
308     int i;
309     Xen9pfsDev *xen_9pdev = container_of(xendev, Xen9pfsDev, xendev);
310     V9fsState *s = &xen_9pdev->state;
311     QemuOpts *fsdev;
312 
313     if (xenstore_read_fe_int(&xen_9pdev->xendev, "num-rings",
314                              &xen_9pdev->num_rings) == -1 ||
315         xen_9pdev->num_rings > MAX_RINGS || xen_9pdev->num_rings < 1) {
316         return -1;
317     }
318 
319     xen_9pdev->rings = g_malloc0(xen_9pdev->num_rings * sizeof(Xen9pfsRing));
320     for (i = 0; i < xen_9pdev->num_rings; i++) {
321         char *str;
322         int ring_order;
323 
324         xen_9pdev->rings[i].priv = xen_9pdev;
325         xen_9pdev->rings[i].evtchn = -1;
326         xen_9pdev->rings[i].local_port = -1;
327 
328         str = g_strdup_printf("ring-ref%u", i);
329         if (xenstore_read_fe_int(&xen_9pdev->xendev, str,
330                                  &xen_9pdev->rings[i].ref) == -1) {
331             g_free(str);
332             goto out;
333         }
334         g_free(str);
335         str = g_strdup_printf("event-channel-%u", i);
336         if (xenstore_read_fe_int(&xen_9pdev->xendev, str,
337                                  &xen_9pdev->rings[i].evtchn) == -1) {
338             g_free(str);
339             goto out;
340         }
341         g_free(str);
342 
343         xen_9pdev->rings[i].intf =  xengnttab_map_grant_ref(
344                 xen_9pdev->xendev.gnttabdev,
345                 xen_9pdev->xendev.dom,
346                 xen_9pdev->rings[i].ref,
347                 PROT_READ | PROT_WRITE);
348         if (!xen_9pdev->rings[i].intf) {
349             goto out;
350         }
351         ring_order = xen_9pdev->rings[i].intf->ring_order;
352         if (ring_order > MAX_RING_ORDER) {
353             goto out;
354         }
355         xen_9pdev->rings[i].ring_order = ring_order;
356         xen_9pdev->rings[i].data = xengnttab_map_domain_grant_refs(
357                 xen_9pdev->xendev.gnttabdev,
358                 (1 << ring_order),
359                 xen_9pdev->xendev.dom,
360                 xen_9pdev->rings[i].intf->ref,
361                 PROT_READ | PROT_WRITE);
362         if (!xen_9pdev->rings[i].data) {
363             goto out;
364         }
365         xen_9pdev->rings[i].ring.in = xen_9pdev->rings[i].data;
366         xen_9pdev->rings[i].ring.out = xen_9pdev->rings[i].data +
367                                        XEN_FLEX_RING_SIZE(ring_order);
368 
369         xen_9pdev->rings[i].bh = qemu_bh_new(xen_9pfs_bh, &xen_9pdev->rings[i]);
370         xen_9pdev->rings[i].out_cons = 0;
371         xen_9pdev->rings[i].out_size = 0;
372         xen_9pdev->rings[i].inprogress = false;
373 
374 
375         xen_9pdev->rings[i].evtchndev = xenevtchn_open(NULL, 0);
376         if (xen_9pdev->rings[i].evtchndev == NULL) {
377             goto out;
378         }
379         qemu_set_cloexec(xenevtchn_fd(xen_9pdev->rings[i].evtchndev));
380         xen_9pdev->rings[i].local_port = xenevtchn_bind_interdomain
381                                             (xen_9pdev->rings[i].evtchndev,
382                                              xendev->dom,
383                                              xen_9pdev->rings[i].evtchn);
384         if (xen_9pdev->rings[i].local_port == -1) {
385             xen_pv_printf(xendev, 0,
386                           "xenevtchn_bind_interdomain failed port=%d\n",
387                           xen_9pdev->rings[i].evtchn);
388             goto out;
389         }
390         xen_pv_printf(xendev, 2, "bind evtchn port %d\n", xendev->local_port);
391         qemu_set_fd_handler(xenevtchn_fd(xen_9pdev->rings[i].evtchndev),
392                 xen_9pfs_evtchn_event, NULL, &xen_9pdev->rings[i]);
393     }
394 
395     xen_9pdev->security_model = xenstore_read_be_str(xendev, "security_model");
396     xen_9pdev->path = xenstore_read_be_str(xendev, "path");
397     xen_9pdev->id = s->fsconf.fsdev_id =
398         g_strdup_printf("xen9p%d", xendev->dev);
399     xen_9pdev->tag = s->fsconf.tag = xenstore_read_fe_str(xendev, "tag");
400     v9fs_register_transport(s, &xen_9p_transport);
401     fsdev = qemu_opts_create(qemu_find_opts("fsdev"),
402             s->fsconf.tag,
403             1, NULL);
404     qemu_opt_set(fsdev, "fsdriver", "local", NULL);
405     qemu_opt_set(fsdev, "path", xen_9pdev->path, NULL);
406     qemu_opt_set(fsdev, "security_model", xen_9pdev->security_model, NULL);
407     qemu_opts_set_id(fsdev, s->fsconf.fsdev_id);
408     qemu_fsdev_add(fsdev);
409     v9fs_device_realize_common(s, NULL);
410 
411     return 0;
412 
413 out:
414     xen_9pfs_free(xendev);
415     return -1;
416 }
417 
418 static void xen_9pfs_alloc(struct XenDevice *xendev)
419 {
420     xenstore_write_be_str(xendev, "versions", VERSIONS);
421     xenstore_write_be_int(xendev, "max-rings", MAX_RINGS);
422     xenstore_write_be_int(xendev, "max-ring-page-order", MAX_RING_ORDER);
423 }
424 
425 static void xen_9pfs_disconnect(struct XenDevice *xendev)
426 {
427     /* Dynamic hotplug of PV filesystems at runtime is not supported. */
428 }
429 
430 struct XenDevOps xen_9pfs_ops = {
431     .size       = sizeof(Xen9pfsDev),
432     .flags      = DEVOPS_FLAG_NEED_GNTDEV,
433     .alloc      = xen_9pfs_alloc,
434     .init       = xen_9pfs_init,
435     .initialise = xen_9pfs_connect,
436     .disconnect = xen_9pfs_disconnect,
437     .free       = xen_9pfs_free,
438 };
439