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xen/gntdev: use mmu_interval_notifier_insert 

gntdev simply wants to monitor a specific VMA for any notifier events,
this can be done straightforwardly using mmu_interval_notifier_insert()
over the VMA's VA range.

The notifier should be attached until the original VMA is destroyed.

It is unclear if any of this is even sane, but at least a lot of duplicate
code is removed.

Link: https://lore.kernel.org/r/20191112202231.3856-15-jgg@ziepe.ca
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
This commit is contained in:
Jason Gunthorpe 2019-11-12 16:22:31 -04:00
parent a22dd50640
commit d3eeb1d77c
2 changed files with 49 additions and 138 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
drivers/xen/gntdev-common.h
View File

@ -21,15 +21,8 @@ struct gntdev_dmabuf_priv;
struct gntdev_priv {
/* Maps with visible offsets in the file descriptor. */
struct list_head maps;
/*
* Maps that are not visible; will be freed on munmap.
* Only populated if populate_freeable_maps == 1
*/
struct list_head freeable_maps;
/* lock protects maps and freeable_maps. */
struct mutex lock;
struct mm_struct *mm;
struct mmu_notifier mn;
#ifdef CONFIG_XEN_GRANT_DMA_ALLOC
/* Device for which DMA memory is allocated. */
@ -49,6 +42,7 @@ struct gntdev_unmap_notify {
};
struct gntdev_grant_map {
struct mmu_interval_notifier notifier;
struct list_head next;
struct vm_area_struct *vma;
int index;

179
drivers/xen/gntdev.c
View File

@ -63,7 +63,6 @@ MODULE_PARM_DESC(limit, "Maximum number of grants that may be mapped by "
static atomic_t pages_mapped = ATOMIC_INIT(0);
static int use_ptemod;
#define populate_freeable_maps use_ptemod
static int unmap_grant_pages(struct gntdev_grant_map *map,
int offset, int pages);
@ -249,12 +248,6 @@ void gntdev_put_map(struct gntdev_priv *priv, struct gntdev_grant_map *map)
evtchn_put(map->notify.event);
}
if (populate_freeable_maps && priv) {
mutex_lock(&priv->lock);
list_del(&map->next);
mutex_unlock(&priv->lock);
}
if (map->pages && !use_ptemod)
unmap_grant_pages(map, 0, map->count);
gntdev_free_map(map);
@ -444,16 +437,9 @@ static void gntdev_vma_close(struct vm_area_struct *vma)
pr_debug("gntdev_vma_close %p\n", vma);
if (use_ptemod) {
/* It is possible that an mmu notifier could be running
* concurrently, so take priv->lock to ensure that the vma won't
* vanishing during the unmap_grant_pages call, since we will
* spin here until that completes. Such a concurrent call will
* not do any unmapping, since that has been done prior to
* closing the vma, but it may still iterate the unmap_ops list.
*/
mutex_lock(&priv->lock);
WARN_ON(map->vma != vma);
mmu_interval_notifier_remove(&map->notifier);
map->vma = NULL;
mutex_unlock(&priv->lock);
}
vma->vm_private_data = NULL;
gntdev_put_map(priv, map);
@ -475,109 +461,44 @@ static const struct vm_operations_struct gntdev_vmops = {
/* ------------------------------------------------------------------ */
static bool in_range(struct gntdev_grant_map *map,
unsigned long start, unsigned long end)
{
if (!map->vma)
return false;
if (map->vma->vm_start >= end)
return false;
if (map->vma->vm_end <= start)
return false;
return true;
}
static int unmap_if_in_range(struct gntdev_grant_map *map,
unsigned long start, unsigned long end,
bool blockable)
static bool gntdev_invalidate(struct mmu_interval_notifier *mn,
const struct mmu_notifier_range *range,
unsigned long cur_seq)
{
struct gntdev_grant_map *map =
container_of(mn, struct gntdev_grant_map, notifier);
unsigned long mstart, mend;
int err;
if (!in_range(map, start, end))
return 0;
if (!mmu_notifier_range_blockable(range))
return false;
if (!blockable)
return -EAGAIN;
/*
* If the VMA is split or otherwise changed the notifier is not
* updated, but we don't want to process VA's outside the modified
* VMA. FIXME: It would be much more understandable to just prevent
* modifying the VMA in the first place.
*/
if (map->vma->vm_start >= range->end ||
map->vma->vm_end <= range->start)
return true;
mstart = max(start, map->vma->vm_start);
mend = min(end, map->vma->vm_end);
mstart = max(range->start, map->vma->vm_start);
mend = min(range->end, map->vma->vm_end);
pr_debug("map %d+%d (%lx %lx), range %lx %lx, mrange %lx %lx\n",
map->index, map->count,
map->vma->vm_start, map->vma->vm_end,
start, end, mstart, mend);
range->start, range->end, mstart, mend);
err = unmap_grant_pages(map,
(mstart - map->vma->vm_start) >> PAGE_SHIFT,
(mend - mstart) >> PAGE_SHIFT);
WARN_ON(err);
return 0;
return true;
}
static int mn_invl_range_start(struct mmu_notifier *mn,
const struct mmu_notifier_range *range)
{
struct gntdev_priv *priv = container_of(mn, struct gntdev_priv, mn);
struct gntdev_grant_map *map;
int ret = 0;
if (mmu_notifier_range_blockable(range))
mutex_lock(&priv->lock);
else if (!mutex_trylock(&priv->lock))
return -EAGAIN;
list_for_each_entry(map, &priv->maps, next) {
ret = unmap_if_in_range(map, range->start, range->end,
mmu_notifier_range_blockable(range));
if (ret)
goto out_unlock;
}
list_for_each_entry(map, &priv->freeable_maps, next) {
ret = unmap_if_in_range(map, range->start, range->end,
mmu_notifier_range_blockable(range));
if (ret)
goto out_unlock;
}
out_unlock:
mutex_unlock(&priv->lock);
return ret;
}
static void mn_release(struct mmu_notifier *mn,
struct mm_struct *mm)
{
struct gntdev_priv *priv = container_of(mn, struct gntdev_priv, mn);
struct gntdev_grant_map *map;
int err;
mutex_lock(&priv->lock);
list_for_each_entry(map, &priv->maps, next) {
if (!map->vma)
continue;
pr_debug("map %d+%d (%lx %lx)\n",
map->index, map->count,
map->vma->vm_start, map->vma->vm_end);
err = unmap_grant_pages(map, /* offset */ 0, map->count);
WARN_ON(err);
}
list_for_each_entry(map, &priv->freeable_maps, next) {
if (!map->vma)
continue;
pr_debug("map %d+%d (%lx %lx)\n",
map->index, map->count,
map->vma->vm_start, map->vma->vm_end);
err = unmap_grant_pages(map, /* offset */ 0, map->count);
WARN_ON(err);
}
mutex_unlock(&priv->lock);
}
static const struct mmu_notifier_ops gntdev_mmu_ops = {
.release = mn_release,
.invalidate_range_start = mn_invl_range_start,
static const struct mmu_interval_notifier_ops gntdev_mmu_ops = {
.invalidate = gntdev_invalidate,
};
/* ------------------------------------------------------------------ */
@ -592,7 +513,6 @@ static int gntdev_open(struct inode *inode, struct file *flip)
return -ENOMEM;
INIT_LIST_HEAD(&priv->maps);
INIT_LIST_HEAD(&priv->freeable_maps);
mutex_init(&priv->lock);
#ifdef CONFIG_XEN_GNTDEV_DMABUF
@ -604,17 +524,6 @@ static int gntdev_open(struct inode *inode, struct file *flip)
}
#endif
if (use_ptemod) {
priv->mm = get_task_mm(current);
if (!priv->mm) {
kfree(priv);
return -ENOMEM;
}
priv->mn.ops = &gntdev_mmu_ops;
ret = mmu_notifier_register(&priv->mn, priv->mm);
mmput(priv->mm);
}
if (ret) {
kfree(priv);
return ret;
@ -644,16 +553,12 @@ static int gntdev_release(struct inode *inode, struct file *flip)
list_del(&map->next);
gntdev_put_map(NULL /* already removed */, map);
}
WARN_ON(!list_empty(&priv->freeable_maps));
mutex_unlock(&priv->lock);
#ifdef CONFIG_XEN_GNTDEV_DMABUF
gntdev_dmabuf_fini(priv->dmabuf_priv);
#endif
if (use_ptemod)
mmu_notifier_unregister(&priv->mn, priv->mm);
kfree(priv);
return 0;
}
@ -714,8 +619,6 @@ static long gntdev_ioctl_unmap_grant_ref(struct gntdev_priv *priv,
map = gntdev_find_map_index(priv, op.index >> PAGE_SHIFT, op.count);
if (map) {
list_del(&map->next);
if (populate_freeable_maps)
list_add_tail(&map->next, &priv->freeable_maps);
err = 0;
}
mutex_unlock(&priv->lock);
@ -1087,11 +990,6 @@ static int gntdev_mmap(struct file *flip, struct vm_area_struct *vma)
goto unlock_out;
if (use_ptemod && map->vma)
goto unlock_out;
if (use_ptemod && priv->mm != vma->vm_mm) {
pr_warn("Huh? Other mm?\n");
goto unlock_out;
}
refcount_inc(&map->users);
vma->vm_ops = &gntdev_vmops;
@ -1102,10 +1000,6 @@ static int gntdev_mmap(struct file *flip, struct vm_area_struct *vma)
vma->vm_flags |= VM_DONTCOPY;
vma->vm_private_data = map;
if (use_ptemod)
map->vma = vma;
if (map->flags) {
if ((vma->vm_flags & VM_WRITE) &&
(map->flags & GNTMAP_readonly))
@ -1116,8 +1010,28 @@ static int gntdev_mmap(struct file *flip, struct vm_area_struct *vma)
map->flags |= GNTMAP_readonly;
}
if (use_ptemod) {
map->vma = vma;
err = mmu_interval_notifier_insert_locked(
&map->notifier, vma->vm_mm, vma->vm_start,
vma->vm_end - vma->vm_start, &gntdev_mmu_ops);
if (err)
goto out_unlock_put;
}
mutex_unlock(&priv->lock);
/*
* gntdev takes the address of the PTE in find_grant_ptes() and passes
* it to the hypervisor in gntdev_map_grant_pages(). The purpose of
* the notifier is to prevent the hypervisor pointer to the PTE from
* going stale.
*
* Since this vma's mappings can't be touched without the mmap_sem,
* and we are holding it now, there is no need for the notifier_range
* locking pattern.
*/
mmu_interval_read_begin(&map->notifier);
if (use_ptemod) {
map->pages_vm_start = vma->vm_start;
err = apply_to_page_range(vma->vm_mm, vma->vm_start,
@ -1166,8 +1080,11 @@ out_unlock_put:
mutex_unlock(&priv->lock);
out_put_map:
if (use_ptemod) {
map->vma = NULL;
unmap_grant_pages(map, 0, map->count);
if (map->vma) {
mmu_interval_notifier_remove(&map->notifier);
map->vma = NULL;
}
}
gntdev_put_map(priv, map);
return err;