x86/xen: safely map and unmap grant frames when in atomic context
arch_gnttab_map_frames() and arch_gnttab_unmap_frames() are called in atomic context but were calling alloc_vm_area() which might sleep. Also, if a driver attempts to allocate a grant ref from an interrupt and the table needs expanding, then the CPU may already by in lazy MMU mode and apply_to_page_range() will BUG when it tries to re-enable lazy MMU mode. These two functions are only used in PV guests. Introduce arch_gnttab_init() to allocates the virtual address space in advance. Avoid the use of apply_to_page_range() by using saving and using the array of PTE addresses from the alloc_vm_area() call. N.B. 'alloc_vm_area' pre-allocates the pagetable so there is no need to worry about having to do a PGD/PUD/PMD walk (like apply_to_page_range does) and we can instead do set_pte. Signed-off-by: David Vrabel <david.vrabel@citrix.com> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> ---- [v2: Add comment about alloc_vm_area] [v3: Fix compile error found by 0-day bot]
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a2c5ae65ad
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162e371712
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@ -51,3 +51,8 @@ int arch_gnttab_map_status(uint64_t *frames, unsigned long nr_gframes,
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{
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return -ENOSYS;
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}
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int arch_gnttab_init(unsigned long nr_shared, unsigned long nr_status)
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{
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return 0;
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}
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@ -36,99 +36,133 @@
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#include <linux/sched.h>
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#include <linux/mm.h>
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#include <linux/slab.h>
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#include <linux/vmalloc.h>
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#include <xen/interface/xen.h>
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#include <xen/page.h>
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#include <xen/grant_table.h>
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#include <xen/xen.h>
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#include <asm/pgtable.h>
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static int map_pte_fn(pte_t *pte, struct page *pmd_page,
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unsigned long addr, void *data)
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{
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unsigned long **frames = (unsigned long **)data;
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set_pte_at(&init_mm, addr, pte, mfn_pte((*frames)[0], PAGE_KERNEL));
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(*frames)++;
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return 0;
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}
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/*
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* This function is used to map shared frames to store grant status. It is
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* different from map_pte_fn above, the frames type here is uint64_t.
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*/
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static int map_pte_fn_status(pte_t *pte, struct page *pmd_page,
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unsigned long addr, void *data)
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{
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uint64_t **frames = (uint64_t **)data;
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set_pte_at(&init_mm, addr, pte, mfn_pte((*frames)[0], PAGE_KERNEL));
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(*frames)++;
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return 0;
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}
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static int unmap_pte_fn(pte_t *pte, struct page *pmd_page,
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unsigned long addr, void *data)
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{
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set_pte_at(&init_mm, addr, pte, __pte(0));
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return 0;
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}
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static struct gnttab_vm_area {
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struct vm_struct *area;
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pte_t **ptes;
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} gnttab_shared_vm_area, gnttab_status_vm_area;
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int arch_gnttab_map_shared(unsigned long *frames, unsigned long nr_gframes,
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unsigned long max_nr_gframes,
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void **__shared)
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{
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int rc;
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void *shared = *__shared;
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unsigned long addr;
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unsigned long i;
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if (shared == NULL) {
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struct vm_struct *area =
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alloc_vm_area(PAGE_SIZE * max_nr_gframes, NULL);
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BUG_ON(area == NULL);
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shared = area->addr;
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*__shared = shared;
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if (shared == NULL)
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*__shared = shared = gnttab_shared_vm_area.area->addr;
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addr = (unsigned long)shared;
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for (i = 0; i < nr_gframes; i++) {
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set_pte_at(&init_mm, addr, gnttab_shared_vm_area.ptes[i],
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mfn_pte(frames[i], PAGE_KERNEL));
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addr += PAGE_SIZE;
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}
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rc = apply_to_page_range(&init_mm, (unsigned long)shared,
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PAGE_SIZE * nr_gframes,
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map_pte_fn, &frames);
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return rc;
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return 0;
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}
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int arch_gnttab_map_status(uint64_t *frames, unsigned long nr_gframes,
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unsigned long max_nr_gframes,
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grant_status_t **__shared)
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{
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int rc;
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grant_status_t *shared = *__shared;
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unsigned long addr;
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unsigned long i;
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if (shared == NULL) {
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/* No need to pass in PTE as we are going to do it
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* in apply_to_page_range anyhow. */
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struct vm_struct *area =
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alloc_vm_area(PAGE_SIZE * max_nr_gframes, NULL);
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BUG_ON(area == NULL);
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shared = area->addr;
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*__shared = shared;
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if (shared == NULL)
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*__shared = shared = gnttab_status_vm_area.area->addr;
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addr = (unsigned long)shared;
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for (i = 0; i < nr_gframes; i++) {
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set_pte_at(&init_mm, addr, gnttab_status_vm_area.ptes[i],
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mfn_pte(frames[i], PAGE_KERNEL));
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addr += PAGE_SIZE;
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}
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rc = apply_to_page_range(&init_mm, (unsigned long)shared,
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PAGE_SIZE * nr_gframes,
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map_pte_fn_status, &frames);
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return rc;
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return 0;
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}
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void arch_gnttab_unmap(void *shared, unsigned long nr_gframes)
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{
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apply_to_page_range(&init_mm, (unsigned long)shared,
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PAGE_SIZE * nr_gframes, unmap_pte_fn, NULL);
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pte_t **ptes;
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unsigned long addr;
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unsigned long i;
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if (shared == gnttab_status_vm_area.area->addr)
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ptes = gnttab_status_vm_area.ptes;
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else
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ptes = gnttab_shared_vm_area.ptes;
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addr = (unsigned long)shared;
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for (i = 0; i < nr_gframes; i++) {
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set_pte_at(&init_mm, addr, ptes[i], __pte(0));
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addr += PAGE_SIZE;
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}
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}
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static int arch_gnttab_valloc(struct gnttab_vm_area *area, unsigned nr_frames)
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{
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area->ptes = kmalloc(sizeof(pte_t *) * nr_frames, GFP_KERNEL);
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if (area->ptes == NULL)
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return -ENOMEM;
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area->area = alloc_vm_area(PAGE_SIZE * nr_frames, area->ptes);
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if (area->area == NULL) {
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kfree(area->ptes);
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return -ENOMEM;
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}
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return 0;
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}
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static void arch_gnttab_vfree(struct gnttab_vm_area *area)
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{
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free_vm_area(area->area);
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kfree(area->ptes);
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}
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int arch_gnttab_init(unsigned long nr_shared, unsigned long nr_status)
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{
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int ret;
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if (!xen_pv_domain())
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return 0;
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ret = arch_gnttab_valloc(&gnttab_shared_vm_area, nr_shared);
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if (ret < 0)
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return ret;
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/*
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* Always allocate the space for the status frames in case
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* we're migrated to a host with V2 support.
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*/
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ret = arch_gnttab_valloc(&gnttab_status_vm_area, nr_status);
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if (ret < 0)
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goto err;
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return 0;
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err:
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arch_gnttab_vfree(&gnttab_shared_vm_area);
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return -ENOMEM;
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}
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#ifdef CONFIG_XEN_PVH
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#include <xen/balloon.h>
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#include <xen/events.h>
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#include <xen/xen.h>
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#include <linux/slab.h>
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static int __init xlated_setup_gnttab_pages(void)
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{
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@ -1195,18 +1195,20 @@ static int gnttab_expand(unsigned int req_entries)
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int gnttab_init(void)
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{
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int i;
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unsigned long max_nr_grant_frames;
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unsigned int max_nr_glist_frames, nr_glist_frames;
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unsigned int nr_init_grefs;
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int ret;
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gnttab_request_version();
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max_nr_grant_frames = gnttab_max_grant_frames();
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nr_grant_frames = 1;
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/* Determine the maximum number of frames required for the
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* grant reference free list on the current hypervisor.
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*/
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BUG_ON(grefs_per_grant_frame == 0);
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max_nr_glist_frames = (gnttab_max_grant_frames() *
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max_nr_glist_frames = (max_nr_grant_frames *
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grefs_per_grant_frame / RPP);
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gnttab_list = kmalloc(max_nr_glist_frames * sizeof(grant_ref_t *),
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@ -1223,6 +1225,11 @@ int gnttab_init(void)
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}
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}
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ret = arch_gnttab_init(max_nr_grant_frames,
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nr_status_frames(max_nr_grant_frames));
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if (ret < 0)
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goto ini_nomem;
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if (gnttab_setup() < 0) {
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ret = -ENODEV;
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goto ini_nomem;
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@ -170,6 +170,7 @@ gnttab_set_unmap_op(struct gnttab_unmap_grant_ref *unmap, phys_addr_t addr,
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unmap->dev_bus_addr = 0;
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}
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int arch_gnttab_init(unsigned long nr_shared, unsigned long nr_status);
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int arch_gnttab_map_shared(xen_pfn_t *frames, unsigned long nr_gframes,
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unsigned long max_nr_gframes,
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void **__shared);
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