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@xxxxxxxxxxxxx>
> ---
> 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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