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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
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@@ -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;