* [PATCH] vhost-user: Fix out of order vring host notification handling
@ 2022-10-18 2:36 Yajun Wu
2022-10-18 10:34 ` Alex Bennée
0 siblings, 1 reply; 2+ messages in thread
From: Yajun Wu @ 2022-10-18 2:36 UTC (permalink / raw)
To: qemu-devel, mst, alex.bennee, yajunw; +Cc: Parav Pandit
vhost backend sends host notification for every VQ. If backend creates
VQs in parallel, the VHOST_USER_SLAVE_VRING_HOST_NOTIFIER_MSG may
arrive to QEMU in different order than incremental queue index order.
For example VQ 1's message arrive earlier than VQ 0's:
After alloc VhostUserHostNotifier for VQ 1. GPtrArray becomes
[ nil, VQ1 pointer ]
After alloc VhostUserHostNotifier for VQ 0. GPtrArray becomes
[ VQ0 pointer, nil, VQ1 pointer ]
This is wrong. fetch_notifier will return NULL for VQ 1 in
vhost_user_get_vring_base, causes host notifier miss removal(leak).
The fix is to remove current element from GPtrArray, make the right
position for element to insert.
Fixes: 503e355465 ("virtio/vhost-user: dynamically assign VhostUserHostNotifiers")
Signed-off-by: Yajun Wu <yajunw@nvidia.com>
Acked-by: Parav Pandit <parav@nvidia.com>
---
hw/virtio/vhost-user.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
index 03415b6c95..d256ce589b 100644
--- a/hw/virtio/vhost-user.c
+++ b/hw/virtio/vhost-user.c
@@ -1543,6 +1543,11 @@ static VhostUserHostNotifier *fetch_or_create_notifier(VhostUserState *u,
n = g_ptr_array_index(u->notifiers, idx);
if (!n) {
+ /*
+ * In case notification arrive out-of-order,
+ * make room for current index.
+ */
+ g_ptr_array_remove_index(u->notifiers, idx);
n = g_new0(VhostUserHostNotifier, 1);
n->idx = idx;
g_ptr_array_insert(u->notifiers, idx, n);
--
2.27.0
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] vhost-user: Fix out of order vring host notification handling
2022-10-18 2:36 [PATCH] vhost-user: Fix out of order vring host notification handling Yajun Wu
@ 2022-10-18 10:34 ` Alex Bennée
0 siblings, 0 replies; 2+ messages in thread
From: Alex Bennée @ 2022-10-18 10:34 UTC (permalink / raw)
To: Yajun Wu; +Cc: qemu-devel, mst, Parav Pandit
Yajun Wu <yajunw@nvidia.com> writes:
> vhost backend sends host notification for every VQ. If backend creates
> VQs in parallel, the VHOST_USER_SLAVE_VRING_HOST_NOTIFIER_MSG may
> arrive to QEMU in different order than incremental queue index order.
>
> For example VQ 1's message arrive earlier than VQ 0's:
> After alloc VhostUserHostNotifier for VQ 1. GPtrArray becomes
>
> [ nil, VQ1 pointer ]
>
> After alloc VhostUserHostNotifier for VQ 0. GPtrArray becomes
>
> [ VQ0 pointer, nil, VQ1 pointer ]
>
> This is wrong. fetch_notifier will return NULL for VQ 1 in
> vhost_user_get_vring_base, causes host notifier miss removal(leak).
>
> The fix is to remove current element from GPtrArray, make the right
> position for element to insert.
>
> Fixes: 503e355465 ("virtio/vhost-user: dynamically assign VhostUserHostNotifiers")
> Signed-off-by: Yajun Wu <yajunw@nvidia.com>
> Acked-by: Parav Pandit <parav@nvidia.com>
>
> ---
> hw/virtio/vhost-user.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
> index 03415b6c95..d256ce589b 100644
> --- a/hw/virtio/vhost-user.c
> +++ b/hw/virtio/vhost-user.c
> @@ -1543,6 +1543,11 @@ static VhostUserHostNotifier *fetch_or_create_notifier(VhostUserState *u,
>
> n = g_ptr_array_index(u->notifiers, idx);
> if (!n) {
> + /*
> + * In case notification arrive out-of-order,
> + * make room for current index.
> + */
> + g_ptr_array_remove_index(u->notifiers, idx);
> n = g_new0(VhostUserHostNotifier, 1);
> n->idx = idx;
> g_ptr_array_insert(u->notifiers, idx, n);
Ahh reading the description of g_ptr_array_insert() it doesn't
explicitly say it shuffles the data currently at index up but I can see
from the code it does. I guess you can imply it from the other function
descriptions.
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
--
Alex Bennée
^ permalink raw reply [flat|nested] 2+ messages in thread
end of thread, other threads:[~2022-10-18 10:51 UTC | newest]
Thread overview: 2+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2022-10-18 2:36 [PATCH] vhost-user: Fix out of order vring host notification handling Yajun Wu
2022-10-18 10:34 ` Alex Bennée
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.