2022-05-23 07:09:34

by Eugenio Perez Martin

Subject: [PATCH 2/4] vhost-vdpa: introduce STOP backend feature bit

Userland knows if it can stop the device or not by checking this feature
bit.

It's only offered if the vdpa driver backend implements the stop()
operation callback, and try to set it if the backend does not offer that
callback is an error.

Signed-off-by: Eugenio Pérez <[email protected]>
---
drivers/vhost/vdpa.c | 13 +++++++++++++
include/uapi/linux/vhost_types.h | 2 ++
2 files changed, 15 insertions(+)

diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
index 1f1d1c425573..a325bc259afb 100644
--- a/drivers/vhost/vdpa.c
+++ b/drivers/vhost/vdpa.c
@@ -347,6 +347,14 @@ static long vhost_vdpa_set_config(struct vhost_vdpa *v,
return 0;
}

+static bool vhost_vdpa_can_stop(const struct vhost_vdpa *v)
+{
+ struct vdpa_device *vdpa = v->vdpa;
+ const struct vdpa_config_ops *ops = vdpa->config;
+
+ return ops->stop;
+}
+
static long vhost_vdpa_get_features(struct vhost_vdpa *v, u64 __user *featurep)
{
struct vdpa_device *vdpa = v->vdpa;
@@ -577,6 +585,9 @@ static long vhost_vdpa_unlocked_ioctl(struct file *filep,
return -EFAULT;
if (features & ~VHOST_VDPA_BACKEND_FEATURES)
return -EOPNOTSUPP;
+ if ((features & VHOST_BACKEND_F_STOP) &&
+ !vhost_vdpa_can_stop(v))
+ return -EOPNOTSUPP;
vhost_set_backend_features(&v->vdev, features);
return 0;
}
@@ -624,6 +635,8 @@ static long vhost_vdpa_unlocked_ioctl(struct file *filep,
break;
case VHOST_GET_BACKEND_FEATURES:
features = VHOST_VDPA_BACKEND_FEATURES;
+ if (vhost_vdpa_can_stop(v))
+ features |= VHOST_BACKEND_F_STOP;
if (copy_to_user(featurep, &features, sizeof(features)))
r = -EFAULT;
break;
diff --git a/include/uapi/linux/vhost_types.h b/include/uapi/linux/vhost_types.h
index 634cee485abb..2758e665791b 100644
--- a/include/uapi/linux/vhost_types.h
+++ b/include/uapi/linux/vhost_types.h
@@ -161,5 +161,7 @@ struct vhost_vdpa_iova_range {
* message
*/
#define VHOST_BACKEND_F_IOTLB_ASID 0x3
+/* Stop device from processing virtqueue buffers */
+#define VHOST_BACKEND_F_STOP 0x4

#endif
--
2.27.0

2022-05-23 07:16:38

by Si-Wei Liu

Subject: Re: [PATCH 2/4] vhost-vdpa: introduce STOP backend feature bit

On 5/20/2022 10:23 AM, Eugenio Pérez wrote:
> Userland knows if it can stop the device or not by checking this feature
> bit.
>
> It's only offered if the vdpa driver backend implements the stop()
> operation callback, and try to set it if the backend does not offer that
> callback is an error.
>
> Signed-off-by: Eugenio Pérez <[email protected]>
> ---
> drivers/vhost/vdpa.c | 13 +++++++++++++
> include/uapi/linux/vhost_types.h | 2 ++
> 2 files changed, 15 insertions(+)
>
> diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
> index 1f1d1c425573..a325bc259afb 100644
> --- a/drivers/vhost/vdpa.c
> +++ b/drivers/vhost/vdpa.c
> @@ -347,6 +347,14 @@ static long vhost_vdpa_set_config(struct vhost_vdpa *v,
> return 0;
> }
>
> +static bool vhost_vdpa_can_stop(const struct vhost_vdpa *v)
> +{
> + struct vdpa_device *vdpa = v->vdpa;
> + const struct vdpa_config_ops *ops = vdpa->config;
> +
> + return ops->stop;
> +}
> +
> static long vhost_vdpa_get_features(struct vhost_vdpa *v, u64 __user *featurep)
> {
> struct vdpa_device *vdpa = v->vdpa;
> @@ -577,6 +585,9 @@ static long vhost_vdpa_unlocked_ioctl(struct file *filep,
> return -EFAULT;
> if (features & ~VHOST_VDPA_BACKEND_FEATURES)
> return -EOPNOTSUPP;
> + if ((features & VHOST_BACKEND_F_STOP) &&
VHOST_BACKEND_F_STOP is not part of VHOST_VDPA_BACKEND_FEATURES. There's
no chance for VHOST_BACKEND_F_STOP to get here.

-Siwei
> + !vhost_vdpa_can_stop(v))
> + return -EOPNOTSUPP;
> vhost_set_backend_features(&v->vdev, features);
> return 0;
> }
> @@ -624,6 +635,8 @@ static long vhost_vdpa_unlocked_ioctl(struct file *filep,
> break;
> case VHOST_GET_BACKEND_FEATURES:
> features = VHOST_VDPA_BACKEND_FEATURES;
> + if (vhost_vdpa_can_stop(v))
> + features |= VHOST_BACKEND_F_STOP;
> if (copy_to_user(featurep, &features, sizeof(features)))
> r = -EFAULT;
> break;
> diff --git a/include/uapi/linux/vhost_types.h b/include/uapi/linux/vhost_types.h
> index 634cee485abb..2758e665791b 100644
> --- a/include/uapi/linux/vhost_types.h
> +++ b/include/uapi/linux/vhost_types.h
> @@ -161,5 +161,7 @@ struct vhost_vdpa_iova_range {
> * message
> */
> #define VHOST_BACKEND_F_IOTLB_ASID 0x3
> +/* Stop device from processing virtqueue buffers */
> +#define VHOST_BACKEND_F_STOP 0x4
>
> #endif

2022-05-23 09:59:33

by Eugenio Perez Martin

Subject: Re: [PATCH 2/4] vhost-vdpa: introduce STOP backend feature bit

On Sat, May 21, 2022 at 12:25 PM Si-Wei Liu <[email protected]> wrote:
>
>
>
> On 5/20/2022 10:23 AM, Eugenio Pérez wrote:
> > Userland knows if it can stop the device or not by checking this feature
> > bit.
> >
> > It's only offered if the vdpa driver backend implements the stop()
> > operation callback, and try to set it if the backend does not offer that
> > callback is an error.
> >
> > Signed-off-by: Eugenio Pérez <[email protected]>
> > ---
> > drivers/vhost/vdpa.c | 13 +++++++++++++
> > include/uapi/linux/vhost_types.h | 2 ++
> > 2 files changed, 15 insertions(+)
> >
> > diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
> > index 1f1d1c425573..a325bc259afb 100644
> > --- a/drivers/vhost/vdpa.c
> > +++ b/drivers/vhost/vdpa.c
> > @@ -347,6 +347,14 @@ static long vhost_vdpa_set_config(struct vhost_vdpa *v,
> > return 0;
> > }
> >
> > +static bool vhost_vdpa_can_stop(const struct vhost_vdpa *v)
> > +{
> > + struct vdpa_device *vdpa = v->vdpa;
> > + const struct vdpa_config_ops *ops = vdpa->config;
> > +
> > + return ops->stop;
> > +}
> > +
> > static long vhost_vdpa_get_features(struct vhost_vdpa *v, u64 __user *featurep)
> > {
> > struct vdpa_device *vdpa = v->vdpa;
> > @@ -577,6 +585,9 @@ static long vhost_vdpa_unlocked_ioctl(struct file *filep,
> > return -EFAULT;
> > if (features & ~VHOST_VDPA_BACKEND_FEATURES)
> > return -EOPNOTSUPP;
> > + if ((features & VHOST_BACKEND_F_STOP) &&
> VHOST_BACKEND_F_STOP is not part of VHOST_VDPA_BACKEND_FEATURES. There's
> no chance for VHOST_BACKEND_F_STOP to get here.
>

That's right. I think I missed to backport your patches about set
backend_features only once in my testing.

I will re-test with the latest qemu master, thanks!

> -Siwei
> > + !vhost_vdpa_can_stop(v))
> > + return -EOPNOTSUPP;
> > vhost_set_backend_features(&v->vdev, features);
> > return 0;
> > }
> > @@ -624,6 +635,8 @@ static long vhost_vdpa_unlocked_ioctl(struct file *filep,
> > break;
> > case VHOST_GET_BACKEND_FEATURES:
> > features = VHOST_VDPA_BACKEND_FEATURES;
> > + if (vhost_vdpa_can_stop(v))
> > + features |= VHOST_BACKEND_F_STOP;
> > if (copy_to_user(featurep, &features, sizeof(features)))
> > r = -EFAULT;
> > break;
> > diff --git a/include/uapi/linux/vhost_types.h b/include/uapi/linux/vhost_types.h
> > index 634cee485abb..2758e665791b 100644
> > --- a/include/uapi/linux/vhost_types.h
> > +++ b/include/uapi/linux/vhost_types.h
> > @@ -161,5 +161,7 @@ struct vhost_vdpa_iova_range {
> > * message
> > */
> > #define VHOST_BACKEND_F_IOTLB_ASID 0x3
> > +/* Stop device from processing virtqueue buffers */
> > +#define VHOST_BACKEND_F_STOP 0x4
> >
> > #endif
>