[Xen-devel] [PATCH 2/2] xen/gnt{dev, alloc}: reserve event channels for notify

[Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>]

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@xxxxxxxxxxxxx>
---
 drivers/xen/gntalloc.c |   14 +++++++++++++-
 drivers/xen/gntdev.c   |   11 +++++++++++
 2 files changed, 24 insertions(+), 1 deletions(-)

diff --git a/drivers/xen/gntalloc.c b/drivers/xen/gntalloc.c
index f6832f4..cff862b 100644
--- a/drivers/xen/gntalloc.c
+++ b/drivers/xen/gntalloc.c
@@ -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);
+               put_evtchn_reservation(gref->notify.event);
+       }
 
        gref->notify.flags = 0;
 
@@ -396,6 +398,16 @@ static long gntalloc_ioctl_unmap_notify(struct 
gntalloc_file_private_data *priv,
                goto unlock_out;
        }
 
+       if (op.action & UNMAP_NOTIFY_SEND_EVENT) {
+               if (get_evtchn_reservation(op.event_channel_port)) {
+                       rc = -EINVAL;
+                       goto unlock_out;
+               }
+       }
+
+       if (gref->notify.flags & UNMAP_NOTIFY_SEND_EVENT)
+               put_evtchn_reservation(gref->notify.event);
+
        gref->notify.flags = op.action;
        gref->notify.pgoff = pgoff;
        gref->notify.event = op.event_channel_port;
diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
index f914b26..8de393c 100644
--- a/drivers/xen/gntdev.c
+++ b/drivers/xen/gntdev.c
@@ -190,6 +190,7 @@ static void gntdev_put_map(struct grant_map *map)
 
        if (map->notify.flags & UNMAP_NOTIFY_SEND_EVENT) {
                notify_remote_via_evtchn(map->notify.event);
+               put_evtchn_reservation(map->notify.event);
        }
 
        if (map->pages) {
@@ -596,6 +597,16 @@ static long gntdev_ioctl_notify(struct gntdev_priv *priv, 
void __user *u)
                goto unlock_out;
        }
 
+       if (op.action & UNMAP_NOTIFY_SEND_EVENT) {
+               if (get_evtchn_reservation(op.event_channel_port)) {
+                       rc = -EINVAL;
+                       goto unlock_out;
+               }
+       }
+
+       if (map->notify.flags & UNMAP_NOTIFY_SEND_EVENT)
+               put_evtchn_reservation(map->notify.event);
+
        map->notify.flags = op.action;
        map->notify.addr = op.index - (map->index << PAGE_SHIFT);
        map->notify.event = op.event_channel_port;
-- 
1.7.6


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