* Re: [PATCH v2] vduse: Fix race condition between resetting and irq injecting
[not found] <20210929083050.88-1-xieyongji@bytedance.com>
@ 2021-09-29 8:40 ` Jason Wang
[not found] ` <CACycT3vp-kxMGVL8W=ebQgOFt_aWs5Y33ZML-Up8KuwsTfQCwA@mail.gmail.com>
2021-10-13 11:10 ` Michael S. Tsirkin
1 sibling, 1 reply; 4+ messages in thread
From: Jason Wang @ 2021-09-29 8:40 UTC (permalink / raw)
To: Xie Yongji; +Cc: virtualization, mst
On Wed, Sep 29, 2021 at 4:32 PM Xie Yongji <xieyongji@bytedance.com> wrote:
>
> The interrupt might be triggered after a reset since there is
> no synchronization between resetting and irq injecting. And it
> might break something if the interrupt is delayed until a new
> round of device initialization.
>
> Fixes: c8a6153b6c59 ("vduse: Introduce VDUSE - vDPA Device in Userspace")
> Signed-off-by: Xie Yongji <xieyongji@bytedance.com>
> ---
> drivers/vdpa/vdpa_user/vduse_dev.c | 37 +++++++++++++++++++++++++------------
> 1 file changed, 25 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c
> index cefb301b2ee4..841667a896dd 100644
> --- a/drivers/vdpa/vdpa_user/vduse_dev.c
> +++ b/drivers/vdpa/vdpa_user/vduse_dev.c
> @@ -80,6 +80,7 @@ struct vduse_dev {
> struct vdpa_callback config_cb;
> struct work_struct inject;
> spinlock_t irq_lock;
> + struct rw_semaphore rwsem;
> int minor;
> bool broken;
> bool connected;
> @@ -410,6 +411,8 @@ static void vduse_dev_reset(struct vduse_dev *dev)
> if (domain->bounce_map)
> vduse_domain_reset_bounce_map(domain);
>
> + down_write(&dev->rwsem);
> +
> dev->status = 0;
> dev->driver_features = 0;
> dev->generation++;
> @@ -443,6 +446,8 @@ static void vduse_dev_reset(struct vduse_dev *dev)
> flush_work(&vq->inject);
> flush_work(&vq->kick);
> }
> +
> + up_write(&dev->rwsem);
Rethink about this, do we need to sync set_status() as well?
Thanks
> }
>
> static int vduse_vdpa_set_vq_address(struct vdpa_device *vdpa, u16 idx,
> @@ -885,6 +890,23 @@ static void vduse_vq_irq_inject(struct work_struct *work)
> spin_unlock_irq(&vq->irq_lock);
> }
>
> +static int vduse_dev_queue_irq_work(struct vduse_dev *dev,
> + struct work_struct *irq_work)
> +{
> + int ret = -EINVAL;
> +
> + down_read(&dev->rwsem);
> + if (!(dev->status & VIRTIO_CONFIG_S_DRIVER_OK))
> + goto unlock;
> +
> + ret = 0;
> + queue_work(vduse_irq_wq, irq_work);
> +unlock:
> + up_read(&dev->rwsem);
> +
> + return ret;
> +}
> +
> static long vduse_dev_ioctl(struct file *file, unsigned int cmd,
> unsigned long arg)
> {
> @@ -966,12 +988,7 @@ static long vduse_dev_ioctl(struct file *file, unsigned int cmd,
> break;
> }
> case VDUSE_DEV_INJECT_CONFIG_IRQ:
> - ret = -EINVAL;
> - if (!(dev->status & VIRTIO_CONFIG_S_DRIVER_OK))
> - break;
> -
> - ret = 0;
> - queue_work(vduse_irq_wq, &dev->inject);
> + ret = vduse_dev_queue_irq_work(dev, &dev->inject);
> break;
> case VDUSE_VQ_SETUP: {
> struct vduse_vq_config config;
> @@ -1049,10 +1066,6 @@ static long vduse_dev_ioctl(struct file *file, unsigned int cmd,
> case VDUSE_VQ_INJECT_IRQ: {
> u32 index;
>
> - ret = -EINVAL;
> - if (!(dev->status & VIRTIO_CONFIG_S_DRIVER_OK))
> - break;
> -
> ret = -EFAULT;
> if (get_user(index, (u32 __user *)argp))
> break;
> @@ -1061,9 +1074,8 @@ static long vduse_dev_ioctl(struct file *file, unsigned int cmd,
> if (index >= dev->vq_num)
> break;
>
> - ret = 0;
> index = array_index_nospec(index, dev->vq_num);
> - queue_work(vduse_irq_wq, &dev->vqs[index].inject);
> + ret = vduse_dev_queue_irq_work(dev, &dev->vqs[index].inject);
> break;
> }
> default:
> @@ -1144,6 +1156,7 @@ static struct vduse_dev *vduse_dev_create(void)
> INIT_LIST_HEAD(&dev->send_list);
> INIT_LIST_HEAD(&dev->recv_list);
> spin_lock_init(&dev->irq_lock);
> + init_rwsem(&dev->rwsem);
>
> INIT_WORK(&dev->inject, vduse_dev_irq_inject);
> init_waitqueue_head(&dev->waitq);
> --
> 2.11.0
>
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^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH v2] vduse: Fix race condition between resetting and irq injecting
[not found] ` <CACycT3vp-kxMGVL8W=ebQgOFt_aWs5Y33ZML-Up8KuwsTfQCwA@mail.gmail.com>
@ 2021-10-13 11:06 ` Michael S. Tsirkin
0 siblings, 0 replies; 4+ messages in thread
From: Michael S. Tsirkin @ 2021-10-13 11:06 UTC (permalink / raw)
To: Yongji Xie; +Cc: virtualization
On Wed, Sep 29, 2021 at 04:50:24PM +0800, Yongji Xie wrote:
> On Wed, Sep 29, 2021 at 4:41 PM Jason Wang <jasowang@redhat.com> wrote:
> >
> > On Wed, Sep 29, 2021 at 4:32 PM Xie Yongji <xieyongji@bytedance.com> wrote:
> > >
> > > The interrupt might be triggered after a reset since there is
> > > no synchronization between resetting and irq injecting. And it
> > > might break something if the interrupt is delayed until a new
> > > round of device initialization.
> > >
> > > Fixes: c8a6153b6c59 ("vduse: Introduce VDUSE - vDPA Device in Userspace")
> > > Signed-off-by: Xie Yongji <xieyongji@bytedance.com>
> > > ---
> > > drivers/vdpa/vdpa_user/vduse_dev.c | 37 +++++++++++++++++++++++++------------
> > > 1 file changed, 25 insertions(+), 12 deletions(-)
> > >
> > > diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c
> > > index cefb301b2ee4..841667a896dd 100644
> > > --- a/drivers/vdpa/vdpa_user/vduse_dev.c
> > > +++ b/drivers/vdpa/vdpa_user/vduse_dev.c
> > > @@ -80,6 +80,7 @@ struct vduse_dev {
> > > struct vdpa_callback config_cb;
> > > struct work_struct inject;
> > > spinlock_t irq_lock;
> > > + struct rw_semaphore rwsem;
> > > int minor;
> > > bool broken;
> > > bool connected;
> > > @@ -410,6 +411,8 @@ static void vduse_dev_reset(struct vduse_dev *dev)
> > > if (domain->bounce_map)
> > > vduse_domain_reset_bounce_map(domain);
> > >
> > > + down_write(&dev->rwsem);
> > > +
> > > dev->status = 0;
> > > dev->driver_features = 0;
> > > dev->generation++;
> > > @@ -443,6 +446,8 @@ static void vduse_dev_reset(struct vduse_dev *dev)
> > > flush_work(&vq->inject);
> > > flush_work(&vq->kick);
> > > }
> > > +
> > > + up_write(&dev->rwsem);
> >
> > Rethink about this, do we need to sync set_status() as well?
> >
>
> I'm not sure. But I don't see any case that needs synchronization.
>
> Thanks,
> Yongji
Well you are testing under a lock but it can change at any time...
--
MST
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^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH v2] vduse: Fix race condition between resetting and irq injecting
[not found] <20210929083050.88-1-xieyongji@bytedance.com>
2021-09-29 8:40 ` [PATCH v2] vduse: Fix race condition between resetting and irq injecting Jason Wang
@ 2021-10-13 11:10 ` Michael S. Tsirkin
[not found] ` <CACycT3tSP-Vxt_u+ow71ZzxBjKuGycZ1LqUrbjQ6Ew3ehX7kqw@mail.gmail.com>
1 sibling, 1 reply; 4+ messages in thread
From: Michael S. Tsirkin @ 2021-10-13 11:10 UTC (permalink / raw)
To: Xie Yongji; +Cc: virtualization
On Wed, Sep 29, 2021 at 04:30:50PM +0800, Xie Yongji wrote:
> The interrupt might be triggered after a reset since there is
> no synchronization between resetting and irq injecting.
In fact, irq_lock is already used to synchronize with
irqs. Why isn't taking and releasing it enough?
> And it
> might break something if the interrupt is delayed until a new
> round of device initialization.
>
> Fixes: c8a6153b6c59 ("vduse: Introduce VDUSE - vDPA Device in Userspace")
> Signed-off-by: Xie Yongji <xieyongji@bytedance.com>
> ---
> drivers/vdpa/vdpa_user/vduse_dev.c | 37 +++++++++++++++++++++++++------------
> 1 file changed, 25 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c
> index cefb301b2ee4..841667a896dd 100644
> --- a/drivers/vdpa/vdpa_user/vduse_dev.c
> +++ b/drivers/vdpa/vdpa_user/vduse_dev.c
> @@ -80,6 +80,7 @@ struct vduse_dev {
> struct vdpa_callback config_cb;
> struct work_struct inject;
> spinlock_t irq_lock;
> + struct rw_semaphore rwsem;
> int minor;
> bool broken;
> bool connected;
What does this lock protect? Use a more descriptive name pls,
and maybe add a comment.
> @@ -410,6 +411,8 @@ static void vduse_dev_reset(struct vduse_dev *dev)
> if (domain->bounce_map)
> vduse_domain_reset_bounce_map(domain);
>
> + down_write(&dev->rwsem);
> +
> dev->status = 0;
> dev->driver_features = 0;
> dev->generation++;
> @@ -443,6 +446,8 @@ static void vduse_dev_reset(struct vduse_dev *dev)
> flush_work(&vq->inject);
> flush_work(&vq->kick);
> }
> +
> + up_write(&dev->rwsem);
> }
>
> static int vduse_vdpa_set_vq_address(struct vdpa_device *vdpa, u16 idx,
> @@ -885,6 +890,23 @@ static void vduse_vq_irq_inject(struct work_struct *work)
> spin_unlock_irq(&vq->irq_lock);
> }
>
> +static int vduse_dev_queue_irq_work(struct vduse_dev *dev,
> + struct work_struct *irq_work)
> +{
> + int ret = -EINVAL;
> +
> + down_read(&dev->rwsem);
> + if (!(dev->status & VIRTIO_CONFIG_S_DRIVER_OK))
> + goto unlock;
> +
> + ret = 0;
> + queue_work(vduse_irq_wq, irq_work);
> +unlock:
> + up_read(&dev->rwsem);
> +
> + return ret;
> +}
> +
> static long vduse_dev_ioctl(struct file *file, unsigned int cmd,
> unsigned long arg)
> {
so that's a lot of overhead for an irq.
Normally the way to address races like this is to add
flushing to the reset path, not locking to irq path.
> @@ -966,12 +988,7 @@ static long vduse_dev_ioctl(struct file *file, unsigned int cmd,
> break;
> }
> case VDUSE_DEV_INJECT_CONFIG_IRQ:
> - ret = -EINVAL;
> - if (!(dev->status & VIRTIO_CONFIG_S_DRIVER_OK))
> - break;
> -
> - ret = 0;
> - queue_work(vduse_irq_wq, &dev->inject);
> + ret = vduse_dev_queue_irq_work(dev, &dev->inject);
> break;
> case VDUSE_VQ_SETUP: {
> struct vduse_vq_config config;
> @@ -1049,10 +1066,6 @@ static long vduse_dev_ioctl(struct file *file, unsigned int cmd,
> case VDUSE_VQ_INJECT_IRQ: {
> u32 index;
>
> - ret = -EINVAL;
> - if (!(dev->status & VIRTIO_CONFIG_S_DRIVER_OK))
> - break;
> -
> ret = -EFAULT;
> if (get_user(index, (u32 __user *)argp))
> break;
> @@ -1061,9 +1074,8 @@ static long vduse_dev_ioctl(struct file *file, unsigned int cmd,
> if (index >= dev->vq_num)
> break;
>
> - ret = 0;
> index = array_index_nospec(index, dev->vq_num);
> - queue_work(vduse_irq_wq, &dev->vqs[index].inject);
> + ret = vduse_dev_queue_irq_work(dev, &dev->vqs[index].inject);
> break;
> }
> default:
> @@ -1144,6 +1156,7 @@ static struct vduse_dev *vduse_dev_create(void)
> INIT_LIST_HEAD(&dev->send_list);
> INIT_LIST_HEAD(&dev->recv_list);
> spin_lock_init(&dev->irq_lock);
> + init_rwsem(&dev->rwsem);
>
> INIT_WORK(&dev->inject, vduse_dev_irq_inject);
> init_waitqueue_head(&dev->waitq);
> --
> 2.11.0
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^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH v2] vduse: Fix race condition between resetting and irq injecting
[not found] ` <CACycT3tSP-Vxt_u+ow71ZzxBjKuGycZ1LqUrbjQ6Ew3ehX7kqw@mail.gmail.com>
@ 2021-10-13 12:34 ` Michael S. Tsirkin
0 siblings, 0 replies; 4+ messages in thread
From: Michael S. Tsirkin @ 2021-10-13 12:34 UTC (permalink / raw)
To: Yongji Xie; +Cc: virtualization
On Wed, Oct 13, 2021 at 08:30:40PM +0800, Yongji Xie wrote:
> On Wed, Oct 13, 2021 at 7:10 PM Michael S. Tsirkin <mst@redhat.com> wrote:
> >
> > On Wed, Sep 29, 2021 at 04:30:50PM +0800, Xie Yongji wrote:
> > > The interrupt might be triggered after a reset since there is
> > > no synchronization between resetting and irq injecting.
> >
> > In fact, irq_lock is already used to synchronize with
> > irqs. Why isn't taking and releasing it enough?
> >
>
> For example:
>
> CPU 0
> CPU1
> ---------
> --------
> vduse_dev_ioctl()
> check DRIVER_OK
>
> vduse_dev_reset()
>
> flush_work(&vq->inject);
> queue_work(vduse_irq_wq, &vq->inject);
>
> virtio_vdpa_probe()
>
> virtio_vdpa_find_vqs()
> vduse_vq_irq_inject()
> vq->cb.callback(vq->cb.private);
>
> set DRIVER_OK
>
> In the above case, the irq callback is still triggered before DRIVER_OK is set.
>
> But now I found it seems to be better to just check DRIVER_OK again in
> vduse_vq_irq_inject().
And then pesumably make sure each time we set status
it's done under the irq lock?
> > > And it
> > > might break something if the interrupt is delayed until a new
> > > round of device initialization.
> > >
> > > Fixes: c8a6153b6c59 ("vduse: Introduce VDUSE - vDPA Device in Userspace")
> > > Signed-off-by: Xie Yongji <xieyongji@bytedance.com>
> > > ---
> > > drivers/vdpa/vdpa_user/vduse_dev.c | 37 +++++++++++++++++++++++++------------
> > > 1 file changed, 25 insertions(+), 12 deletions(-)
> > >
> > > diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c
> > > index cefb301b2ee4..841667a896dd 100644
> > > --- a/drivers/vdpa/vdpa_user/vduse_dev.c
> > > +++ b/drivers/vdpa/vdpa_user/vduse_dev.c
> > > @@ -80,6 +80,7 @@ struct vduse_dev {
> > > struct vdpa_callback config_cb;
> > > struct work_struct inject;
> > > spinlock_t irq_lock;
> > > + struct rw_semaphore rwsem;
> > > int minor;
> > > bool broken;
> > > bool connected;
> >
> > What does this lock protect? Use a more descriptive name pls,
> > and maybe add a comment.
> >
>
> This lock is used to ensure there is no more inflight irq kwork after reset.
>
> >
> > > @@ -410,6 +411,8 @@ static void vduse_dev_reset(struct vduse_dev *dev)
> > > if (domain->bounce_map)
> > > vduse_domain_reset_bounce_map(domain);
> > >
> > > + down_write(&dev->rwsem);
> > > +
> > > dev->status = 0;
> > > dev->driver_features = 0;
> > > dev->generation++;
> > > @@ -443,6 +446,8 @@ static void vduse_dev_reset(struct vduse_dev *dev)
> > > flush_work(&vq->inject);
> > > flush_work(&vq->kick);
> > > }
> > > +
> > > + up_write(&dev->rwsem);
> > > }
> > >
> > > static int vduse_vdpa_set_vq_address(struct vdpa_device *vdpa, u16 idx,
> > > @@ -885,6 +890,23 @@ static void vduse_vq_irq_inject(struct work_struct *work)
> > > spin_unlock_irq(&vq->irq_lock);
> > > }
> > >
> > > +static int vduse_dev_queue_irq_work(struct vduse_dev *dev,
> > > + struct work_struct *irq_work)
> > > +{
> > > + int ret = -EINVAL;
> > > +
> > > + down_read(&dev->rwsem);
> > > + if (!(dev->status & VIRTIO_CONFIG_S_DRIVER_OK))
> > > + goto unlock;
> > > +
> > > + ret = 0;
> > > + queue_work(vduse_irq_wq, irq_work);
> > > +unlock:
> > > + up_read(&dev->rwsem);
> > > +
> > > + return ret;
> > > +}
> > > +
> > > static long vduse_dev_ioctl(struct file *file, unsigned int cmd,
> > > unsigned long arg)
> > > {
> >
> >
> > so that's a lot of overhead for an irq.
> > Normally the way to address races like this is to add
> > flushing to the reset path, not locking to irq path.
> >
>
> Yes, we already call flush_work() in the reset path.
>
> Thanks,
> Yongji
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[not found] <20210929083050.88-1-xieyongji@bytedance.com>
2021-09-29 8:40 ` [PATCH v2] vduse: Fix race condition between resetting and irq injecting Jason Wang
[not found] ` <CACycT3vp-kxMGVL8W=ebQgOFt_aWs5Y33ZML-Up8KuwsTfQCwA@mail.gmail.com>
2021-10-13 11:06 ` Michael S. Tsirkin
2021-10-13 11:10 ` Michael S. Tsirkin
[not found] ` <CACycT3tSP-Vxt_u+ow71ZzxBjKuGycZ1LqUrbjQ6Ew3ehX7kqw@mail.gmail.com>
2021-10-13 12:34 ` Michael S. Tsirkin
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