RE: [PATCH 3/4] virtio: Protect vqs list access
> From: Michael S. Tsirkin
> Sent: Sunday, July 18, 2021 2:11 AM
>
> On Sat, Jul 17, 2021 at 10:42:57AM +0300, Parav Pandit wrote:
> > VQs may be accessed to mark the device broken while they are
> > created/destroyed. Hence protect the access to the vqs list.
> >
> > Fixes: e2dcdfe95c0b ("virtio: virtio_break_device() to mark all
> > virtqueues broken.")
> > Signed-off-by: Parav Pandit
> > ---
> > drivers/virtio/virtio.c | 1 +
> > drivers/virtio/virtio_ring.c | 8
> > include/linux/virtio.h | 1 +
> > 3 files changed, 10 insertions(+)
> >
> > diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c index
> > 4b15c00c0a0a..a0d81e35ec4b 100644
> > --- a/drivers/virtio/virtio.c
> > +++ b/drivers/virtio/virtio.c
> > @@ -355,6 +355,7 @@ int register_virtio_device(struct virtio_device *dev)
> > virtio_add_status(dev, VIRTIO_CONFIG_S_ACKNOWLEDGE);
> >
> > INIT_LIST_HEAD(>vqs);
> > + rwlock_init(>vqs_list_lock);
> >
> > /*
> > * device_add() causes the bus infrastructure to look for a matching
>
> Let's just use a simple spinlock. I don't think we are worried about scaling
> the
> breaking of devices to multiple CPUs.
>
It wasn't the scaling, just wanted to have the clarity on list access. But I
realized that rwlock is bigger size too.
So yeah, will simplify to spinlock in v2.
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Re: [PATCH 3/4] virtio: Protect vqs list access
On Sat, Jul 17, 2021 at 10:42:57AM +0300, Parav Pandit wrote:
> VQs may be accessed to mark the device broken while they are
> created/destroyed. Hence protect the access to the vqs list.
>
> Fixes: e2dcdfe95c0b ("virtio: virtio_break_device() to mark all virtqueues
> broken.")
> Signed-off-by: Parav Pandit
> ---
> drivers/virtio/virtio.c | 1 +
> drivers/virtio/virtio_ring.c | 8
> include/linux/virtio.h | 1 +
> 3 files changed, 10 insertions(+)
>
> diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
> index 4b15c00c0a0a..a0d81e35ec4b 100644
> --- a/drivers/virtio/virtio.c
> +++ b/drivers/virtio/virtio.c
> @@ -355,6 +355,7 @@ int register_virtio_device(struct virtio_device *dev)
> virtio_add_status(dev, VIRTIO_CONFIG_S_ACKNOWLEDGE);
>
> INIT_LIST_HEAD(>vqs);
> + rwlock_init(>vqs_list_lock);
>
> /*
>* device_add() causes the bus infrastructure to look for a matching
Let's just use a simple spinlock. I don't think we are worried about
scaling the breaking of devices to multiple CPUs.
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index d2e1a7a21171..66a91dec39d9 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -1755,7 +1755,9 @@ static struct virtqueue *vring_create_virtqueue_packed(
> cpu_to_le16(vq->packed.event_flags_shadow);
> }
>
> + write_lock(>vqs_list_lock);
> list_add_tail(>vq.list, >vqs);
> + write_unlock(>vqs_list_lock);
> return >vq;
>
> err_desc_extra:
> @@ -2229,7 +2231,9 @@ struct virtqueue *__vring_new_virtqueue(unsigned int
> index,
> memset(vq->split.desc_state, 0, vring.num *
> sizeof(struct vring_desc_state_split));
>
> + write_lock(>vqs_list_lock);
> list_add_tail(>vq.list, >vqs);
> + write_unlock(>vqs_list_lock);
> return >vq;
>
> err_extra:
> @@ -2291,7 +2295,9 @@ void vring_del_virtqueue(struct virtqueue *_vq)
> {
> struct vring_virtqueue *vq = to_vvq(_vq);
>
> + write_lock(>vq.vdev->vqs_list_lock);
> list_del(&_vq->list);
> + write_unlock(>vq.vdev->vqs_list_lock);
>
> if (vq->we_own_ring) {
> if (vq->packed_ring) {
> @@ -2386,12 +2392,14 @@ void virtio_break_device(struct virtio_device *dev)
> {
> struct virtqueue *_vq;
>
> + read_lock(>vqs_list_lock);
> list_for_each_entry(_vq, >vqs, list) {
> struct vring_virtqueue *vq = to_vvq(_vq);
>
> /* Pairs with READ_ONCE() in virtqueue_is_broken(). */
> smp_store_release(>broken, true);
> }
> + read_unlock(>vqs_list_lock);
> }
> EXPORT_SYMBOL_GPL(virtio_break_device);
>
> diff --git a/include/linux/virtio.h b/include/linux/virtio.h
> index b1894e0323fa..1cf77d480ef3 100644
> --- a/include/linux/virtio.h
> +++ b/include/linux/virtio.h
> @@ -115,6 +115,7 @@ struct virtio_device {
> const struct virtio_config_ops *config;
> const struct vringh_config_ops *vringh_config;
> struct list_head vqs;
> + rwlock_t vqs_list_lock;
> u64 features;
> void *priv;
> };
> --
> 2.27.0
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[PATCH 3/4] virtio: Protect vqs list access
VQs may be accessed to mark the device broken while they are
created/destroyed. Hence protect the access to the vqs list.
Fixes: e2dcdfe95c0b ("virtio: virtio_break_device() to mark all virtqueues
broken.")
Signed-off-by: Parav Pandit
---
drivers/virtio/virtio.c | 1 +
drivers/virtio/virtio_ring.c | 8
include/linux/virtio.h | 1 +
3 files changed, 10 insertions(+)
diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
index 4b15c00c0a0a..a0d81e35ec4b 100644
--- a/drivers/virtio/virtio.c
+++ b/drivers/virtio/virtio.c
@@ -355,6 +355,7 @@ int register_virtio_device(struct virtio_device *dev)
virtio_add_status(dev, VIRTIO_CONFIG_S_ACKNOWLEDGE);
INIT_LIST_HEAD(>vqs);
+ rwlock_init(>vqs_list_lock);
/*
* device_add() causes the bus infrastructure to look for a matching
diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index d2e1a7a21171..66a91dec39d9 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -1755,7 +1755,9 @@ static struct virtqueue *vring_create_virtqueue_packed(
cpu_to_le16(vq->packed.event_flags_shadow);
}
+ write_lock(>vqs_list_lock);
list_add_tail(>vq.list, >vqs);
+ write_unlock(>vqs_list_lock);
return >vq;
err_desc_extra:
@@ -2229,7 +2231,9 @@ struct virtqueue *__vring_new_virtqueue(unsigned int
index,
memset(vq->split.desc_state, 0, vring.num *
sizeof(struct vring_desc_state_split));
+ write_lock(>vqs_list_lock);
list_add_tail(>vq.list, >vqs);
+ write_unlock(>vqs_list_lock);
return >vq;
err_extra:
@@ -2291,7 +2295,9 @@ void vring_del_virtqueue(struct virtqueue *_vq)
{
struct vring_virtqueue *vq = to_vvq(_vq);
+ write_lock(>vq.vdev->vqs_list_lock);
list_del(&_vq->list);
+ write_unlock(>vq.vdev->vqs_list_lock);
if (vq->we_own_ring) {
if (vq->packed_ring) {
@@ -2386,12 +2392,14 @@ void virtio_break_device(struct virtio_device *dev)
{
struct virtqueue *_vq;
+ read_lock(>vqs_list_lock);
list_for_each_entry(_vq, >vqs, list) {
struct vring_virtqueue *vq = to_vvq(_vq);
/* Pairs with READ_ONCE() in virtqueue_is_broken(). */
smp_store_release(>broken, true);
}
+ read_unlock(>vqs_list_lock);
}
EXPORT_SYMBOL_GPL(virtio_break_device);
diff --git a/include/linux/virtio.h b/include/linux/virtio.h
index b1894e0323fa..1cf77d480ef3 100644
--- a/include/linux/virtio.h
+++ b/include/linux/virtio.h
@@ -115,6 +115,7 @@ struct virtio_device {
const struct virtio_config_ops *config;
const struct vringh_config_ops *vringh_config;
struct list_head vqs;
+ rwlock_t vqs_list_lock;
u64 features;
void *priv;
};
--
2.27.0
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