/****************************************************************************** * grant_table.c * * Granting foreign access to our memory reservation. * * Copyright (c) 2005-2006, Christopher Clark * Copyright (c) 2004-2005, K A Fraser * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License version 2 * as published by the Free Software Foundation; or, when distributed * separately from the Linux kernel or incorporated into other * software packages, subject to the following license: * * Permission is hereby granted, free of charge, to any person obtaining a copy * of this source file (the "Software"), to deal in the Software without * restriction, including without limitation the rights to use, copy, modify, * merge, publish, distribute, sublicense, and/or sell copies of the Software, * and to permit persons to whom the Software is furnished to do so, subject to * the following conditions: * * The above copyright notice and this permission notice shall be included in * all copies or substantial portions of the Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS * IN THE SOFTWARE. */ #include <linux/module.h> #include <linux/sched.h> #include <linux/mm.h> #include <linux/vmalloc.h> #include <linux/uaccess.h> #include <xen/interface/xen.h> #include <xen/page.h> #include <xen/grant_table.h> #include <asm/xen/hypercall.h> #include <asm/pgtable.h> #include <asm/sync_bitops.h> /* External tools reserve first few grant table entries. */ #define NR_RESERVED_ENTRIES 8 #define GNTTAB_LIST_END 0xffffffff #define GREFS_PER_GRANT_FRAME (PAGE_SIZE / sizeof(struct grant_entry)) static grant_ref_t **gnttab_list; static unsigned int nr_grant_frames; static unsigned int boot_max_nr_grant_frames; static int gnttab_free_count; static grant_ref_t gnttab_free_head; static DEFINE_SPINLOCK(gnttab_list_lock); static struct grant_entry *shared; static struct gnttab_free_callback *gnttab_free_callback_list; static int gnttab_expand(unsigned int req_entries); #define RPP (PAGE_SIZE / sizeof(grant_ref_t)) static inline grant_ref_t *__gnttab_entry(grant_ref_t entry) { return &gnttab_list[(entry) / RPP][(entry) % RPP]; } /* This can be used as an l-value */ #define gnttab_entry(entry) (*__gnttab_entry(entry)) static int get_free_entries(unsigned count) { unsigned long flags; int ref, rc; grant_ref_t head; spin_lock_irqsave(&gnttab_list_lock, flags); if ((gnttab_free_count < count) && ((rc = gnttab_expand(count - gnttab_free_count)) < 0)) { spin_unlock_irqrestore(&gnttab_list_lock, flags); return rc; } ref = head = gnttab_free_head; gnttab_free_count -= count; while (count-- > 1) head = gnttab_entry(head); gnttab_free_head = gnttab_entry(head); gnttab_entry(head) = GNTTAB_LIST_END; spin_unlock_irqrestore(&gnttab_list_lock, flags); return ref; } static void do_free_callbacks(void) { struct gnttab_free_callback *callback, *next; callback = gnttab_free_callback_list; gnttab_free_callback_list = NULL; while (callback != NULL) { next = callback->next; if (gnttab_free_count >= callback->count) { callback->next = NULL; callback->fn(callback->arg); } else { callback->next = gnttab_free_callback_list; gnttab_free_callback_list = callback; } callback = next; } } static inline void check_free_callbacks(void) { if (unlikely(gnttab_free_callback_list)) do_free_callbacks(); } static void put_free_entry(grant_ref_t ref) { unsigned long flags; spin_lock_irqsave(&gnttab_list_lock, flags); gnttab_entry(ref) = gnttab_free_head; gnttab_free_head = ref; gnttab_free_count++; check_free_callbacks(); spin_unlock_irqrestore(&gnttab_list_lock, flags); } static void update_grant_entry(grant_ref_t ref, domid_t domid, unsigned long frame, unsigned flags) { /* * Introducing a valid entry into the grant table: * 1. Write ent->domid. * 2. Write ent->frame: * GTF_permit_access: Frame to which access is permitted. * GTF_accept_transfer: Pseudo-phys frame slot being filled by new * frame, or zero if none. * 3. Write memory barrier (WMB). * 4. Write ent->flags, inc. valid type. */ shared[ref].frame = frame; shared[ref].domid = domid; wmb(); shared[ref].flags = flags; } /* * Public grant-issuing interface functions */ void gnttab_grant_foreign_access_ref(grant_ref_t ref, domid_t domid, unsigned long frame, int readonly) { update_grant_entry(ref, domid, frame, GTF_permit_access | (readonly ? GTF_readonly : 0)); } EXPORT_SYMBOL_GPL(gnttab_grant_foreign_access_ref); int gnttab_grant_foreign_access(domid_t domid, unsigned long frame, int readonly) { int ref; ref = get_free_entries(1); if (unlikely(ref < 0)) return -ENOSPC; gnttab_grant_foreign_access_ref(ref, domid, frame, readonly); return ref; } EXPORT_SYMBOL_GPL(gnttab_grant_foreign_access); int gnttab_query_foreign_access(grant_ref_t ref) { u16 nflags; nflags = shared[ref].flags; return (nflags & (GTF_reading|GTF_writing)); } EXPORT_SYMBOL_GPL(gnttab_query_foreign_access); int gnttab_end_foreign_access_ref(grant_ref_t ref, int readonly) { u16 flags, nflags; nflags = shared[ref].flags; do { flags = nflags; if (flags & (GTF_reading|GTF_writing)) { printk(KERN_ALERT "WARNING: g.e. still in use!\n"); return 0; } } while ((nflags = sync_cmpxchg(&shared[ref].flags, flags, 0)) != flags); return 1; } EXPORT_SYMBOL_GPL(gnttab_end_foreign_access_ref); void gnttab_end_foreign_access(grant_ref_t ref, int readonly, unsigned long page) { if (gnttab_end_foreign_access_ref(ref, readonly)) { put_free_entry(ref); if (page != 0) free_page(page); } else { /* XXX This needs to be fixed so that the ref and page are placed on a list to be freed up later. */ printk(KERN_WARNING "WARNING: leaking g.e. and page still in use!\n"); } } EXPORT_SYMBOL_GPL(gnttab_end_foreign_access); int gnttab_grant_foreign_transfer(domid_t domid, unsigned long pfn) { int ref; ref = get_free_entries(1); if (unlikely(ref < 0)) return -ENOSPC; gnttab_grant_foreign_transfer_ref(ref, domid, pfn); return ref; } EXPORT_SYMBOL_GPL(gnttab_grant_foreign_transfer); void gnttab_grant_foreign_transfer_ref(grant_ref_t ref, domid_t domid, unsigned long pfn) { update_grant_entry(ref, domid, pfn, GTF_accept_transfer); } EXPORT_SYMBOL_GPL(gnttab_grant_foreign_transfer_ref); unsigned long gnttab_end_foreign_transfer_ref(grant_ref_t ref) { unsigned long frame; u16 flags; /* * If a transfer is not even yet started, try to reclaim the grant * reference and return failure (== 0). */ while (!((flags = shared[ref].flags) & GTF_transfer_committed)) { if (sync_cmpxchg(&shared[ref].flags, flags, 0) == flags) return 0; cpu_relax(); } /* If a transfer is in progress then wait until it is completed. */ while (!(flags & GTF_transfer_completed)) { flags = shared[ref].flags; cpu_relax(); } rmb(); /* Read the frame number /after/ reading completion status. */ frame = shared[ref].frame; BUG_ON(frame == 0); return frame; } EXPORT_SYMBOL_GPL(gnttab_end_foreign_transfer_ref); unsigned long gnttab_end_foreign_transfer(grant_ref_t ref) { unsigned long frame = gnttab_end_foreign_transfer_ref(ref); put_free_entry(ref); return frame; } EXPORT_SYMBOL_GPL(gnttab_end_foreign_transfer); void gnttab_free_grant_reference(grant_ref_t ref) { put_free_entry(ref); } EXPORT_SYMBOL_GPL(gnttab_free_grant_reference); void gnttab_free_grant_references(grant_ref_t head) { grant_ref_t ref; unsigned long flags; int count = 1; if (head == GNTTAB_LIST_END) return; spin_lock_irqsave(&gnttab_list_lock, flags); ref = head; while (gnttab_entry(ref) != GNTTAB_LIST_END) { ref = gnttab_entry(ref); count++; } gnttab_entry(ref) = gnttab_free_head; gnttab_free_head = head; gnttab_free_count += count; check_free_callbacks(); spin_unlock_irqrestore(&gnttab_list_lock, flags); } EXPORT_SYMBOL_GPL(gnttab_free_grant_references); int gnttab_alloc_grant_references(u16 count, grant_ref_t *head) { int h = get_free_entries(count); if (h < 0) return -ENOSPC; *head = h; return 0; } EXPORT_SYMBOL_GPL(gnttab_alloc_grant_references); int gnttab_empty_grant_references(const grant_ref_t *private_head) { return (*private_head == GNTTAB_LIST_END); } EXPORT_SYMBOL_GPL(gnttab_empty_grant_references); int gnttab_claim_grant_reference(grant_ref_t *private_head) { grant_ref_t g = *private_head; if (unlikely(g == GNTTAB_LIST_END)) return -ENOSPC; *private_head = gnttab_entry(g); return g; } EXPORT_SYMBOL_GPL(gnttab_claim_grant_reference); void gnttab_release_grant_reference(grant_ref_t *private_head, grant_ref_t release) { gnttab_entry(release) = *private_head; *private_head = release; } EXPORT_SYMBOL_GPL(gnttab_release_grant_reference); void gnttab_request_free_callback(struct gnttab_free_callback *callback, void (*fn)(void *), void *arg, u16 count) { unsigned long flags; spin_lock_irqsave(&gnttab_list_lock, flags); if (callback->next) goto out; callback->fn = fn; callback->arg = arg; callback->count = count; callback->next = gnttab_free_callback_list; gnttab_free_callback_list = callback; check_free_callbacks(); out: spin_unlock_irqrestore(&gnttab_list_lock, flags); } EXPORT_SYMBOL_GPL(gnttab_request_free_callback); void gnttab_cancel_free_callback(struct gnttab_free_callback *callback) { struct gnttab_free_callback **pcb; unsigned long flags; spin_lock_irqsave(&gnttab_list_lock, flags); for (pcb = &gnttab_free_callback_list; *pcb; pcb = &(*pcb)->next) { if (*pcb == callback) { *pcb = callback->next; break; } } spin_unlock_irqrestore(&gnttab_list_lock, flags); } EXPORT_SYMBOL_GPL(gnttab_cancel_free_callback); static int grow_gnttab_list(unsigned int more_frames) { unsigned int new_nr_grant_frames, extra_entries, i; unsigned int nr_glist_frames, new_nr_glist_frames; new_nr_grant_frames = nr_grant_frames + more_frames; extra_entries = more_frames * GREFS_PER_GRANT_FRAME; nr_glist_frames = (nr_grant_frames * GREFS_PER_GRANT_FRAME + RPP - 1) / RPP; new_nr_glist_frames = (new_nr_grant_frames * GREFS_PER_GRANT_FRAME + RPP - 1) / RPP; for (i = nr_glist_frames; i < new_nr_glist_frames; i++) { gnttab_list[i] = (grant_ref_t *)__get_free_page(GFP_ATOMIC); if (!gnttab_list[i]) goto grow_nomem; } for (i = GREFS_PER_GRANT_FRAME * nr_grant_frames; i < GREFS_PER_GRANT_FRAME * new_nr_grant_frames - 1; i++) gnttab_entry(i) = i + 1; gnttab_entry(i) = gnttab_free_head; gnttab_free_head = GREFS_PER_GRANT_FRAME * nr_grant_frames; gnttab_free_count += extra_entries; nr_grant_frames = new_nr_grant_frames; check_free_callbacks(); return 0; grow_nomem: for ( ; i >= nr_glist_frames; i--) free_page((unsigned long) gnttab_list[i]); return -ENOMEM; } static unsigned int __max_nr_grant_frames(void) { struct gnttab_query_size query; int rc; query.dom = DOMID_SELF; rc = HYPERVISOR_grant_table_op(GNTTABOP_query_size, &query, 1); if ((rc < 0) || (query.status != GNTST_okay)) return 4; /* Legacy max supported number of frames */ return query.max_nr_frames; } static inline unsigned int max_nr_grant_frames(void) { unsigned int xen_max = __max_nr_grant_frames(); if (xen_max > boot_max_nr_grant_frames) return boot_max_nr_grant_frames; return xen_max; } static int gnttab_map(unsigned int start_idx, unsigned int end_idx) { struct gnttab_setup_table setup; unsigned long *frames; unsigned int nr_gframes = end_idx + 1; int rc; frames = kmalloc(nr_gframes * sizeof(unsigned long), GFP_ATOMIC); if (!frames) return -ENOMEM; setup.dom = DOMID_SELF; setup.nr_frames = nr_gframes; set_xen_guest_handle(setup.frame_list, frames); rc = HYPERVISOR_grant_table_op(GNTTABOP_setup_table, &setup, 1); if (rc == -ENOSYS) { kfree(frames); return -ENOSYS; } BUG_ON(rc || setup.status); rc = arch_gnttab_map_shared(frames, nr_gframes, max_nr_grant_frames(), &shared); BUG_ON(rc); kfree(frames); return 0; } int gnttab_resume(void) { if (max_nr_grant_frames() < nr_grant_frames) return -ENOSYS; return gnttab_map(0, nr_grant_frames - 1); } int gnttab_suspend(void) { arch_gnttab_unmap_shared(shared, nr_grant_frames); return 0; } static int gnttab_expand(unsigned int req_entries) { int rc; unsigned int cur, extra; cur = nr_grant_frames; extra = ((req_entries + (GREFS_PER_GRANT_FRAME-1)) / GREFS_PER_GRANT_FRAME); if (cur + extra > max_nr_grant_frames()) return -ENOSPC; rc = gnttab_map(cur, cur + extra - 1); if (rc == 0) rc = grow_gnttab_list(extra); return rc; } static int __devinit gnttab_init(void) { int i; unsigned int max_nr_glist_frames, nr_glist_frames; unsigned int nr_init_grefs; if (!xen_domain()) return -ENODEV; nr_grant_frames = 1; boot_max_nr_grant_frames = __max_nr_grant_frames(); /* Determine the maximum number of frames required for the * grant reference free list on the current hypervisor. */ max_nr_glist_frames = (boot_max_nr_grant_frames * GREFS_PER_GRANT_FRAME / RPP); gnttab_list = kmalloc(max_nr_glist_frames * sizeof(grant_ref_t *), GFP_KERNEL); if (gnttab_list == NULL) return -ENOMEM; nr_glist_frames = (nr_grant_frames * GREFS_PER_GRANT_FRAME + RPP - 1) / RPP; for (i = 0; i < nr_glist_frames; i++) { gnttab_list[i] = (grant_ref_t *)__get_free_page(GFP_KERNEL); if (gnttab_list[i] == NULL) goto ini_nomem; } if (gnttab_resume() < 0) return -ENODEV; nr_init_grefs = nr_grant_frames * GREFS_PER_GRANT_FRAME; for (i = NR_RESERVED_ENTRIES; i < nr_init_grefs - 1; i++) gnttab_entry(i) = i + 1; gnttab_entry(nr_init_grefs - 1) = GNTTAB_LIST_END; gnttab_free_count = nr_init_grefs - NR_RESERVED_ENTRIES; gnttab_free_head = NR_RESERVED_ENTRIES; printk("Grant table initialized\n"); return 0; ini_nomem: for (i--; i >= 0; i--) free_page((unsigned long)gnttab_list[i]); kfree(gnttab_list); return -ENOMEM; } core_initcall(gnttab_init);