1 /******************************************************************************
2 * Client-facing interface for the Xenbus driver. In other words, the
3 * interface between the Xenbus and the device-specific code, be it the
4 * frontend or the backend of that driver.
6 * Copyright (C) 2005 XenSource Ltd
8 * This program is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU General Public License version 2
10 * as published by the Free Software Foundation; or, when distributed
11 * separately from the Linux kernel or incorporated into other
12 * software packages, subject to the following license:
14 * Permission is hereby granted, free of charge, to any person obtaining a copy
15 * of this source file (the "Software"), to deal in the Software without
16 * restriction, including without limitation the rights to use, copy, modify,
17 * merge, publish, distribute, sublicense, and/or sell copies of the Software,
18 * and to permit persons to whom the Software is furnished to do so, subject to
19 * the following conditions:
21 * The above copyright notice and this permission notice shall be included in
22 * all copies or substantial portions of the Software.
24 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
25 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
26 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
27 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
28 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
29 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
34 #include <linux/slab.h>
35 #include <linux/types.h>
36 #include <linux/spinlock.h>
37 #include <linux/vmalloc.h>
38 #include <linux/export.h>
39 #include <asm/xen/hypervisor.h>
41 #include <xen/interface/xen.h>
42 #include <xen/interface/event_channel.h>
43 #include <xen/balloon.h>
44 #include <xen/events.h>
45 #include <xen/grant_table.h>
46 #include <xen/xenbus.h>
48 #include <xen/features.h>
52 #define XENBUS_PAGES(_grants) (DIV_ROUND_UP(_grants, XEN_PFN_PER_PAGE))
54 #define XENBUS_MAX_RING_PAGES (XENBUS_PAGES(XENBUS_MAX_RING_GRANTS))
56 struct xenbus_map_node {
57 struct list_head next;
60 struct vm_struct *area;
63 struct page *pages[XENBUS_MAX_RING_PAGES];
64 unsigned long addrs[XENBUS_MAX_RING_GRANTS];
68 grant_handle_t handles[XENBUS_MAX_RING_GRANTS];
69 unsigned int nr_handles;
72 struct map_ring_valloc {
73 struct xenbus_map_node *node;
75 /* Why do we need two arrays? See comment of __xenbus_map_ring */
76 unsigned long addrs[XENBUS_MAX_RING_GRANTS];
77 phys_addr_t phys_addrs[XENBUS_MAX_RING_GRANTS];
79 struct gnttab_map_grant_ref map[XENBUS_MAX_RING_GRANTS];
80 struct gnttab_unmap_grant_ref unmap[XENBUS_MAX_RING_GRANTS];
85 static DEFINE_SPINLOCK(xenbus_valloc_lock);
86 static LIST_HEAD(xenbus_valloc_pages);
88 struct xenbus_ring_ops {
89 int (*map)(struct xenbus_device *dev, struct map_ring_valloc *info,
90 grant_ref_t *gnt_refs, unsigned int nr_grefs,
92 int (*unmap)(struct xenbus_device *dev, void *vaddr);
95 static const struct xenbus_ring_ops *ring_ops __read_mostly;
97 const char *xenbus_strstate(enum xenbus_state state)
99 static const char *const name[] = {
100 [ XenbusStateUnknown ] = "Unknown",
101 [ XenbusStateInitialising ] = "Initialising",
102 [ XenbusStateInitWait ] = "InitWait",
103 [ XenbusStateInitialised ] = "Initialised",
104 [ XenbusStateConnected ] = "Connected",
105 [ XenbusStateClosing ] = "Closing",
106 [ XenbusStateClosed ] = "Closed",
107 [XenbusStateReconfiguring] = "Reconfiguring",
108 [XenbusStateReconfigured] = "Reconfigured",
110 return (state < ARRAY_SIZE(name)) ? name[state] : "INVALID";
112 EXPORT_SYMBOL_GPL(xenbus_strstate);
115 * xenbus_watch_path - register a watch
116 * @dev: xenbus device
117 * @path: path to watch
118 * @watch: watch to register
119 * @callback: callback to register
121 * Register a @watch on the given path, using the given xenbus_watch structure
122 * for storage, and the given @callback function as the callback. Return 0 on
123 * success, or -errno on error. On success, the given @path will be saved as
124 * @watch->node, and remains the caller's to free. On error, @watch->node will
125 * be NULL, the device will switch to %XenbusStateClosing, and the error will
126 * be saved in the store.
128 int xenbus_watch_path(struct xenbus_device *dev, const char *path,
129 struct xenbus_watch *watch,
130 bool (*will_handle)(struct xenbus_watch *,
131 const char *, const char *),
132 void (*callback)(struct xenbus_watch *,
133 const char *, const char *))
138 watch->will_handle = will_handle;
139 watch->callback = callback;
141 err = register_xenbus_watch(watch);
145 watch->will_handle = NULL;
146 watch->callback = NULL;
147 xenbus_dev_fatal(dev, err, "adding watch on %s", path);
152 EXPORT_SYMBOL_GPL(xenbus_watch_path);
156 * xenbus_watch_pathfmt - register a watch on a sprintf-formatted path
157 * @dev: xenbus device
158 * @watch: watch to register
159 * @callback: callback to register
160 * @pathfmt: format of path to watch
162 * Register a watch on the given @path, using the given xenbus_watch
163 * structure for storage, and the given @callback function as the callback.
164 * Return 0 on success, or -errno on error. On success, the watched path
165 * (@path/@path2) will be saved as @watch->node, and becomes the caller's to
166 * kfree(). On error, watch->node will be NULL, so the caller has nothing to
167 * free, the device will switch to %XenbusStateClosing, and the error will be
168 * saved in the store.
170 int xenbus_watch_pathfmt(struct xenbus_device *dev,
171 struct xenbus_watch *watch,
172 bool (*will_handle)(struct xenbus_watch *,
173 const char *, const char *),
174 void (*callback)(struct xenbus_watch *,
175 const char *, const char *),
176 const char *pathfmt, ...)
182 va_start(ap, pathfmt);
183 path = kvasprintf(GFP_NOIO | __GFP_HIGH, pathfmt, ap);
187 xenbus_dev_fatal(dev, -ENOMEM, "allocating path for watch");
190 err = xenbus_watch_path(dev, path, watch, will_handle, callback);
196 EXPORT_SYMBOL_GPL(xenbus_watch_pathfmt);
198 static void xenbus_switch_fatal(struct xenbus_device *, int, int,
202 __xenbus_switch_state(struct xenbus_device *dev,
203 enum xenbus_state state, int depth)
205 /* We check whether the state is currently set to the given value, and
206 if not, then the state is set. We don't want to unconditionally
207 write the given state, because we don't want to fire watches
208 unnecessarily. Furthermore, if the node has gone, we don't write
209 to it, as the device will be tearing down, and we don't want to
210 resurrect that directory.
212 Note that, because of this cached value of our state, this
213 function will not take a caller's Xenstore transaction
214 (something it was trying to in the past) because dev->state
215 would not get reset if the transaction was aborted.
218 struct xenbus_transaction xbt;
222 if (state == dev->state)
228 err = xenbus_transaction_start(&xbt);
230 xenbus_switch_fatal(dev, depth, err, "starting transaction");
234 err = xenbus_scanf(xbt, dev->nodename, "state", "%d", ¤t_state);
238 err = xenbus_printf(xbt, dev->nodename, "state", "%d", state);
240 xenbus_switch_fatal(dev, depth, err, "writing new state");
246 err = xenbus_transaction_end(xbt, abort);
248 if (err == -EAGAIN && !abort)
250 xenbus_switch_fatal(dev, depth, err, "ending transaction");
258 * xenbus_switch_state
259 * @dev: xenbus device
262 * Advertise in the store a change of the given driver to the given new_state.
263 * Return 0 on success, or -errno on error. On error, the device will switch
264 * to XenbusStateClosing, and the error will be saved in the store.
266 int xenbus_switch_state(struct xenbus_device *dev, enum xenbus_state state)
268 return __xenbus_switch_state(dev, state, 0);
271 EXPORT_SYMBOL_GPL(xenbus_switch_state);
273 int xenbus_frontend_closed(struct xenbus_device *dev)
275 xenbus_switch_state(dev, XenbusStateClosed);
276 complete(&dev->down);
279 EXPORT_SYMBOL_GPL(xenbus_frontend_closed);
281 static void xenbus_va_dev_error(struct xenbus_device *dev, int err,
282 const char *fmt, va_list ap)
288 #define PRINTF_BUFFER_SIZE 4096
290 printf_buffer = kmalloc(PRINTF_BUFFER_SIZE, GFP_KERNEL);
294 len = sprintf(printf_buffer, "%i ", -err);
295 vsnprintf(printf_buffer + len, PRINTF_BUFFER_SIZE - len, fmt, ap);
297 dev_err(&dev->dev, "%s\n", printf_buffer);
299 path_buffer = kasprintf(GFP_KERNEL, "error/%s", dev->nodename);
301 xenbus_write(XBT_NIL, path_buffer, "error", printf_buffer);
303 kfree(printf_buffer);
309 * @dev: xenbus device
310 * @err: error to report
311 * @fmt: error message format
313 * Report the given negative errno into the store, along with the given
316 void xenbus_dev_error(struct xenbus_device *dev, int err, const char *fmt, ...)
321 xenbus_va_dev_error(dev, err, fmt, ap);
324 EXPORT_SYMBOL_GPL(xenbus_dev_error);
328 * @dev: xenbus device
329 * @err: error to report
330 * @fmt: error message format
332 * Equivalent to xenbus_dev_error(dev, err, fmt, args), followed by
333 * xenbus_switch_state(dev, XenbusStateClosing) to schedule an orderly
334 * closedown of this driver and its peer.
337 void xenbus_dev_fatal(struct xenbus_device *dev, int err, const char *fmt, ...)
342 xenbus_va_dev_error(dev, err, fmt, ap);
345 xenbus_switch_state(dev, XenbusStateClosing);
347 EXPORT_SYMBOL_GPL(xenbus_dev_fatal);
350 * Equivalent to xenbus_dev_fatal(dev, err, fmt, args), but helps
351 * avoiding recursion within xenbus_switch_state.
353 static void xenbus_switch_fatal(struct xenbus_device *dev, int depth, int err,
354 const char *fmt, ...)
359 xenbus_va_dev_error(dev, err, fmt, ap);
363 __xenbus_switch_state(dev, XenbusStateClosing, 1);
368 * @dev: xenbus device
369 * @vaddr: starting virtual address of the ring
370 * @nr_pages: number of pages to be granted
371 * @grefs: grant reference array to be filled in
373 * Grant access to the given @vaddr to the peer of the given device.
374 * Then fill in @grefs with grant references. Return 0 on success, or
375 * -errno on error. On error, the device will switch to
376 * XenbusStateClosing, and the error will be saved in the store.
378 int xenbus_grant_ring(struct xenbus_device *dev, void *vaddr,
379 unsigned int nr_pages, grant_ref_t *grefs)
383 grant_ref_t gref_head;
385 err = gnttab_alloc_grant_references(nr_pages, &gref_head);
387 xenbus_dev_fatal(dev, err, "granting access to ring page");
391 for (i = 0; i < nr_pages; i++) {
394 if (is_vmalloc_addr(vaddr))
395 gfn = pfn_to_gfn(vmalloc_to_pfn(vaddr));
397 gfn = virt_to_gfn(vaddr);
399 grefs[i] = gnttab_claim_grant_reference(&gref_head);
400 gnttab_grant_foreign_access_ref(grefs[i], dev->otherend_id,
403 vaddr = vaddr + XEN_PAGE_SIZE;
408 EXPORT_SYMBOL_GPL(xenbus_grant_ring);
412 * Allocate an event channel for the given xenbus_device, assigning the newly
413 * created local port to *port. Return 0 on success, or -errno on error. On
414 * error, the device will switch to XenbusStateClosing, and the error will be
415 * saved in the store.
417 int xenbus_alloc_evtchn(struct xenbus_device *dev, evtchn_port_t *port)
419 struct evtchn_alloc_unbound alloc_unbound;
422 alloc_unbound.dom = DOMID_SELF;
423 alloc_unbound.remote_dom = dev->otherend_id;
425 err = HYPERVISOR_event_channel_op(EVTCHNOP_alloc_unbound,
428 xenbus_dev_fatal(dev, err, "allocating event channel");
430 *port = alloc_unbound.port;
434 EXPORT_SYMBOL_GPL(xenbus_alloc_evtchn);
438 * Free an existing event channel. Returns 0 on success or -errno on error.
440 int xenbus_free_evtchn(struct xenbus_device *dev, evtchn_port_t port)
442 struct evtchn_close close;
447 err = HYPERVISOR_event_channel_op(EVTCHNOP_close, &close);
449 xenbus_dev_error(dev, err, "freeing event channel %u", port);
453 EXPORT_SYMBOL_GPL(xenbus_free_evtchn);
457 * xenbus_map_ring_valloc
458 * @dev: xenbus device
459 * @gnt_refs: grant reference array
460 * @nr_grefs: number of grant references
461 * @vaddr: pointer to address to be filled out by mapping
463 * Map @nr_grefs pages of memory into this domain from another
464 * domain's grant table. xenbus_map_ring_valloc allocates @nr_grefs
465 * pages of virtual address space, maps the pages to that address, and
466 * sets *vaddr to that address. Returns 0 on success, and -errno on
467 * error. If an error is returned, device will switch to
468 * XenbusStateClosing and the error message will be saved in XenStore.
470 int xenbus_map_ring_valloc(struct xenbus_device *dev, grant_ref_t *gnt_refs,
471 unsigned int nr_grefs, void **vaddr)
474 struct map_ring_valloc *info;
478 if (nr_grefs > XENBUS_MAX_RING_GRANTS)
481 info = kzalloc(sizeof(*info), GFP_KERNEL);
485 info->node = kzalloc(sizeof(*info->node), GFP_KERNEL);
489 err = ring_ops->map(dev, info, gnt_refs, nr_grefs, vaddr);
495 EXPORT_SYMBOL_GPL(xenbus_map_ring_valloc);
497 /* N.B. sizeof(phys_addr_t) doesn't always equal to sizeof(unsigned
498 * long), e.g. 32-on-64. Caller is responsible for preparing the
499 * right array to feed into this function */
500 static int __xenbus_map_ring(struct xenbus_device *dev,
501 grant_ref_t *gnt_refs,
502 unsigned int nr_grefs,
503 grant_handle_t *handles,
504 struct map_ring_valloc *info,
510 if (nr_grefs > XENBUS_MAX_RING_GRANTS)
513 for (i = 0; i < nr_grefs; i++) {
514 gnttab_set_map_op(&info->map[i], info->phys_addrs[i], flags,
515 gnt_refs[i], dev->otherend_id);
516 handles[i] = INVALID_GRANT_HANDLE;
519 gnttab_batch_map(info->map, i);
521 for (i = 0; i < nr_grefs; i++) {
522 if (info->map[i].status != GNTST_okay) {
523 xenbus_dev_fatal(dev, info->map[i].status,
524 "mapping in shared page %d from domain %d",
525 gnt_refs[i], dev->otherend_id);
528 handles[i] = info->map[i].handle;
534 for (i = j = 0; i < nr_grefs; i++) {
535 if (handles[i] != INVALID_GRANT_HANDLE) {
536 gnttab_set_unmap_op(&info->unmap[j],
538 GNTMAP_host_map, handles[i]);
543 if (HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, info->unmap, j))
547 for (i = 0; i < j; i++) {
548 if (info->unmap[i].status != GNTST_okay) {
559 * @dev: xenbus device
560 * @handles: grant handle array
561 * @nr_handles: number of handles in the array
562 * @vaddrs: addresses to unmap
564 * Unmap memory in this domain that was imported from another domain.
565 * Returns 0 on success and returns GNTST_* on error
566 * (see xen/include/interface/grant_table.h).
568 static int xenbus_unmap_ring(struct xenbus_device *dev, grant_handle_t *handles,
569 unsigned int nr_handles, unsigned long *vaddrs)
571 struct gnttab_unmap_grant_ref unmap[XENBUS_MAX_RING_GRANTS];
575 if (nr_handles > XENBUS_MAX_RING_GRANTS)
578 for (i = 0; i < nr_handles; i++)
579 gnttab_set_unmap_op(&unmap[i], vaddrs[i],
580 GNTMAP_host_map, handles[i]);
582 if (HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, unmap, i))
586 for (i = 0; i < nr_handles; i++) {
587 if (unmap[i].status != GNTST_okay) {
588 xenbus_dev_error(dev, unmap[i].status,
589 "unmapping page at handle %d error %d",
590 handles[i], unmap[i].status);
591 err = unmap[i].status;
599 static void xenbus_map_ring_setup_grant_hvm(unsigned long gfn,
600 unsigned int goffset,
604 struct map_ring_valloc *info = data;
605 unsigned long vaddr = (unsigned long)gfn_to_virt(gfn);
607 info->phys_addrs[info->idx] = vaddr;
608 info->addrs[info->idx] = vaddr;
613 static int xenbus_map_ring_hvm(struct xenbus_device *dev,
614 struct map_ring_valloc *info,
615 grant_ref_t *gnt_ref,
616 unsigned int nr_grefs,
619 struct xenbus_map_node *node = info->node;
623 unsigned int nr_pages = XENBUS_PAGES(nr_grefs);
625 err = xen_alloc_unpopulated_pages(nr_pages, node->hvm.pages);
629 gnttab_foreach_grant(node->hvm.pages, nr_grefs,
630 xenbus_map_ring_setup_grant_hvm,
633 err = __xenbus_map_ring(dev, gnt_ref, nr_grefs, node->handles,
634 info, GNTMAP_host_map, &leaked);
635 node->nr_handles = nr_grefs;
638 goto out_free_ballooned_pages;
640 addr = vmap(node->hvm.pages, nr_pages, VM_MAP | VM_IOREMAP,
644 goto out_xenbus_unmap_ring;
647 node->hvm.addr = addr;
649 spin_lock(&xenbus_valloc_lock);
650 list_add(&node->next, &xenbus_valloc_pages);
651 spin_unlock(&xenbus_valloc_lock);
658 out_xenbus_unmap_ring:
660 xenbus_unmap_ring(dev, node->handles, nr_grefs, info->addrs);
662 pr_alert("leaking %p size %u page(s)",
664 out_free_ballooned_pages:
666 xen_free_unpopulated_pages(nr_pages, node->hvm.pages);
672 * xenbus_unmap_ring_vfree
673 * @dev: xenbus device
674 * @vaddr: addr to unmap
676 * Based on Rusty Russell's skeleton driver's unmap_page.
677 * Unmap a page of memory in this domain that was imported from another domain.
678 * Use xenbus_unmap_ring_vfree if you mapped in your memory with
679 * xenbus_map_ring_valloc (it will free the virtual address space).
680 * Returns 0 on success and returns GNTST_* on error
681 * (see xen/include/interface/grant_table.h).
683 int xenbus_unmap_ring_vfree(struct xenbus_device *dev, void *vaddr)
685 return ring_ops->unmap(dev, vaddr);
687 EXPORT_SYMBOL_GPL(xenbus_unmap_ring_vfree);
690 static int map_ring_apply(pte_t *pte, unsigned long addr, void *data)
692 struct map_ring_valloc *info = data;
694 info->phys_addrs[info->idx++] = arbitrary_virt_to_machine(pte).maddr;
698 static int xenbus_map_ring_pv(struct xenbus_device *dev,
699 struct map_ring_valloc *info,
700 grant_ref_t *gnt_refs,
701 unsigned int nr_grefs,
704 struct xenbus_map_node *node = info->node;
705 struct vm_struct *area;
709 area = get_vm_area(XEN_PAGE_SIZE * nr_grefs, VM_IOREMAP);
712 if (apply_to_page_range(&init_mm, (unsigned long)area->addr,
713 XEN_PAGE_SIZE * nr_grefs, map_ring_apply, info))
715 err = __xenbus_map_ring(dev, gnt_refs, nr_grefs, node->handles,
716 info, GNTMAP_host_map | GNTMAP_contains_pte,
721 node->nr_handles = nr_grefs;
722 node->pv.area = area;
724 spin_lock(&xenbus_valloc_lock);
725 list_add(&node->next, &xenbus_valloc_pages);
726 spin_unlock(&xenbus_valloc_lock);
737 pr_alert("leaking VM area %p size %u page(s)", area, nr_grefs);
742 static int xenbus_unmap_ring_pv(struct xenbus_device *dev, void *vaddr)
744 struct xenbus_map_node *node;
745 struct gnttab_unmap_grant_ref unmap[XENBUS_MAX_RING_GRANTS];
751 spin_lock(&xenbus_valloc_lock);
752 list_for_each_entry(node, &xenbus_valloc_pages, next) {
753 if (node->pv.area->addr == vaddr) {
754 list_del(&node->next);
760 spin_unlock(&xenbus_valloc_lock);
763 xenbus_dev_error(dev, -ENOENT,
764 "can't find mapped virtual address %p", vaddr);
765 return GNTST_bad_virt_addr;
768 for (i = 0; i < node->nr_handles; i++) {
771 memset(&unmap[i], 0, sizeof(unmap[i]));
772 addr = (unsigned long)vaddr + (XEN_PAGE_SIZE * i);
773 unmap[i].host_addr = arbitrary_virt_to_machine(
774 lookup_address(addr, &level)).maddr;
775 unmap[i].dev_bus_addr = 0;
776 unmap[i].handle = node->handles[i];
779 if (HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, unmap, i))
784 for (i = 0; i < node->nr_handles; i++) {
785 if (unmap[i].status != GNTST_okay) {
787 xenbus_dev_error(dev, unmap[i].status,
788 "unmapping page at handle %d error %d",
789 node->handles[i], unmap[i].status);
790 err = unmap[i].status;
796 free_vm_area(node->pv.area);
798 pr_alert("leaking VM area %p size %u page(s)",
799 node->pv.area, node->nr_handles);
805 static const struct xenbus_ring_ops ring_ops_pv = {
806 .map = xenbus_map_ring_pv,
807 .unmap = xenbus_unmap_ring_pv,
811 struct unmap_ring_hvm
814 unsigned long addrs[XENBUS_MAX_RING_GRANTS];
817 static void xenbus_unmap_ring_setup_grant_hvm(unsigned long gfn,
818 unsigned int goffset,
822 struct unmap_ring_hvm *info = data;
824 info->addrs[info->idx] = (unsigned long)gfn_to_virt(gfn);
829 static int xenbus_unmap_ring_hvm(struct xenbus_device *dev, void *vaddr)
832 struct xenbus_map_node *node;
834 struct unmap_ring_hvm info = {
837 unsigned int nr_pages;
839 spin_lock(&xenbus_valloc_lock);
840 list_for_each_entry(node, &xenbus_valloc_pages, next) {
841 addr = node->hvm.addr;
843 list_del(&node->next);
849 spin_unlock(&xenbus_valloc_lock);
852 xenbus_dev_error(dev, -ENOENT,
853 "can't find mapped virtual address %p", vaddr);
854 return GNTST_bad_virt_addr;
857 nr_pages = XENBUS_PAGES(node->nr_handles);
859 gnttab_foreach_grant(node->hvm.pages, node->nr_handles,
860 xenbus_unmap_ring_setup_grant_hvm,
863 rv = xenbus_unmap_ring(dev, node->handles, node->nr_handles,
867 xen_free_unpopulated_pages(nr_pages, node->hvm.pages);
870 WARN(1, "Leaking %p, size %u page(s)\n", vaddr, nr_pages);
877 * xenbus_read_driver_state
878 * @path: path for driver
880 * Return the state of the driver rooted at the given store path, or
881 * XenbusStateUnknown if no state can be read.
883 enum xenbus_state xenbus_read_driver_state(const char *path)
885 enum xenbus_state result;
886 int err = xenbus_gather(XBT_NIL, path, "state", "%d", &result, NULL);
888 result = XenbusStateUnknown;
892 EXPORT_SYMBOL_GPL(xenbus_read_driver_state);
894 static const struct xenbus_ring_ops ring_ops_hvm = {
895 .map = xenbus_map_ring_hvm,
896 .unmap = xenbus_unmap_ring_hvm,
899 void __init xenbus_ring_ops_init(void)
902 if (!xen_feature(XENFEAT_auto_translated_physmap))
903 ring_ops = &ring_ops_pv;
906 ring_ops = &ring_ops_hvm;