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xen/gnt{dev,alloc}: reserve event channels for notify

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When using the unmap notify ioctl, the event channel used for
notification needs to be reserved to avoid it being deallocated prior to
sending the notification.

Signed-off-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
This commit is contained in:
Daniel De Graaf 2011-10-27 17:58:49 -04:00 committed by Konrad Rzeszutek Wilk
parent 8ca19a8937
commit 0cc678f850
2 changed files with 50 additions and 2 deletions
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21
drivers/xen/gntalloc.c
View file

@ -178,8 +178,10 @@ static void __del_gref(struct gntalloc_gref *gref)
tmp[gref->notify.pgoff] = 0;
kunmap(gref->page);
}
if (gref->notify.flags & UNMAP_NOTIFY_SEND_EVENT)
if (gref->notify.flags & UNMAP_NOTIFY_SEND_EVENT) {
notify_remote_via_evtchn(gref->notify.event);
evtchn_put(gref->notify.event);
}
gref->notify.flags = 0;
@ -396,6 +398,23 @@ static long gntalloc_ioctl_unmap_notify(struct gntalloc_file_private_data *priv,
goto unlock_out;
}
/* We need to grab a reference to the event channel we are going to use
* to send the notify before releasing the reference we may already have
* (if someone has called this ioctl twice). This is required so that
* it is possible to change the clear_byte part of the notification
* without disturbing the event channel part, which may now be the last
* reference to that event channel.
*/
if (op.action & UNMAP_NOTIFY_SEND_EVENT) {
if (evtchn_get(op.event_channel_port)) {
rc = -EINVAL;
goto unlock_out;
}
}
if (gref->notify.flags & UNMAP_NOTIFY_SEND_EVENT)
evtchn_put(gref->notify.event);
gref->notify.flags = op.action;
gref->notify.pgoff = pgoff;
gref->notify.event = op.event_channel_port;

31
drivers/xen/gntdev.c
View file

@ -193,8 +193,10 @@ static void gntdev_put_map(struct grant_map *map)
atomic_sub(map->count, &pages_mapped);
if (map->notify.flags & UNMAP_NOTIFY_SEND_EVENT)
if (map->notify.flags & UNMAP_NOTIFY_SEND_EVENT) {
notify_remote_via_evtchn(map->notify.event);
evtchn_put(map->notify.event);
}
if (map->pages) {
if (!use_ptemod)
@ -599,6 +601,8 @@ static long gntdev_ioctl_notify(struct gntdev_priv *priv, void __user *u)
struct ioctl_gntdev_unmap_notify op;
struct grant_map *map;
int rc;
int out_flags;
unsigned int out_event;
if (copy_from_user(&op, u, sizeof(op)))
return -EFAULT;
@ -606,6 +610,21 @@ static long gntdev_ioctl_notify(struct gntdev_priv *priv, void __user *u)
if (op.action & ~(UNMAP_NOTIFY_CLEAR_BYTE|UNMAP_NOTIFY_SEND_EVENT))
return -EINVAL;
/* We need to grab a reference to the event channel we are going to use
* to send the notify before releasing the reference we may already have
* (if someone has called this ioctl twice). This is required so that
* it is possible to change the clear_byte part of the notification
* without disturbing the event channel part, which may now be the last
* reference to that event channel.
*/
if (op.action & UNMAP_NOTIFY_SEND_EVENT) {
if (evtchn_get(op.event_channel_port))
return -EINVAL;
}
out_flags = op.action;
out_event = op.event_channel_port;
spin_lock(&priv->lock);
list_for_each_entry(map, &priv->maps, next) {
@ -624,12 +643,22 @@ static long gntdev_ioctl_notify(struct gntdev_priv *priv, void __user *u)
goto unlock_out;
}
out_flags = map->notify.flags;
out_event = map->notify.event;
map->notify.flags = op.action;
map->notify.addr = op.index - (map->index << PAGE_SHIFT);
map->notify.event = op.event_channel_port;
rc = 0;
unlock_out:
spin_unlock(&priv->lock);
/* Drop the reference to the event channel we did not save in the map */
if (out_flags & UNMAP_NOTIFY_SEND_EVENT)
evtchn_put(out_event);
return rc;
}