Virtualization - Aug 2021 - [PATCH v1] vdpa/vdpa_sim: Use the negotiated features when calling vringh_init_iotlb

On Tue, Jul 20, 2021 at 10:14:35AM +0300, Eli Cohen
wrote:
>On Tue, Jul 20, 2021 at 08:57:40AM +0200, Stefano Garzarella wrote:
>> On Tue, Jul 20, 2021 at 08:25:33AM +0300, Eli Cohen wrote:
>> > When calling vringh_init_iotlb(), use the negotiated features
which
>> > might be different than the supported features.
>> >
>> > Fixes: 2c53d0f64c06f ("vdpasim: vDPA device simulator")
>> > Signed-off-by: Eli Cohen <elic at nvidia.com>
>> > ---
>> > v0 --> v1:
>> > Update "Fixes" line
>> >
>> > drivers/vdpa/vdpa_sim/vdpa_sim.c | 4 ++--
>> > 1 file changed, 2 insertions(+), 2 deletions(-)
>> >
>> > diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.c
b/drivers/vdpa/vdpa_sim/vdpa_sim.c
>> > index 14e024de5cbf..89a474c7a096 100644
>> > --- a/drivers/vdpa/vdpa_sim/vdpa_sim.c
>> > +++ b/drivers/vdpa/vdpa_sim/vdpa_sim.c
>> > @@ -66,7 +66,7 @@ static void vdpasim_queue_ready(struct vdpasim
*vdpasim, unsigned int idx)
>> > {
>> > 	struct vdpasim_virtqueue *vq = &vdpasim->vqs[idx];
>> >
>> > -	vringh_init_iotlb(&vq->vring,
vdpasim->dev_attr.supported_features,
>> > +	vringh_init_iotlb(&vq->vring, vdpasim->features,
>> > 			  VDPASIM_QUEUE_MAX, false,
>> > 			  (struct vring_desc *)(uintptr_t)vq->desc_addr,
>> > 			  (struct vring_avail *)
>> > @@ -86,7 +86,7 @@ static void vdpasim_vq_reset(struct vdpasim
*vdpasim,
>> > 	vq->device_addr = 0;
>> > 	vq->cb = NULL;
>> > 	vq->private = NULL;
>> > -	vringh_init_iotlb(&vq->vring,
vdpasim->dev_attr.supported_features,
>> > +	vringh_init_iotlb(&vq->vring, vdpasim->features,
>>
>> vdpasim_vq_reset() is called while resetting the device in
vdpasim_reset()
>> where we also set `vdpasim->features = 0` after resetting the vqs,
so maybe
>> it's better to use the supported features here, since the
negotiated ones
>> are related to the previous instance.
>>
>
>I don't think using supported features is valid. Better to make sure
>vringh_init_iotlb() is called after the features have been negotiated.
>
I think the vringh_init_iotlb() call in vdpasim_vq_reset() is just used 
to clean up the `struct vringh`, then it will be initialized in 
vdpasim_queue_ready() when features have already been negotiated.

Maybe here we can pass 0 (to the features parameter) if we don't want to 
use the features supported by the device.

Thanks,
Stefano

On Tue, Jul 20, 2021 at 10:13:27AM +0200, Stefano Garzarella
wrote:
> On Tue, Jul 20, 2021 at 10:14:35AM +0300, Eli Cohen wrote:
> > On Tue, Jul 20, 2021 at 08:57:40AM +0200, Stefano Garzarella wrote:
> > > On Tue, Jul 20, 2021 at 08:25:33AM +0300, Eli Cohen wrote:
> > > > When calling vringh_init_iotlb(), use the negotiated
features which
> > > > might be different than the supported features.
> > > >
> > > > Fixes: 2c53d0f64c06f ("vdpasim: vDPA device
simulator")
> > > > Signed-off-by: Eli Cohen <elic at nvidia.com>
> > > > ---
> > > > v0 --> v1:
> > > > Update "Fixes" line
> > > >
> > > > drivers/vdpa/vdpa_sim/vdpa_sim.c | 4 ++--
> > > > 1 file changed, 2 insertions(+), 2 deletions(-)
> > > >
> > > > diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.c
b/drivers/vdpa/vdpa_sim/vdpa_sim.c
> > > > index 14e024de5cbf..89a474c7a096 100644
> > > > --- a/drivers/vdpa/vdpa_sim/vdpa_sim.c
> > > > +++ b/drivers/vdpa/vdpa_sim/vdpa_sim.c
> > > > @@ -66,7 +66,7 @@ static void vdpasim_queue_ready(struct
vdpasim *vdpasim, unsigned int idx)
> > > > {
> > > > 	struct vdpasim_virtqueue *vq = &vdpasim->vqs[idx];
> > > >
> > > > -	vringh_init_iotlb(&vq->vring,
vdpasim->dev_attr.supported_features,
> > > > +	vringh_init_iotlb(&vq->vring, vdpasim->features,
> > > > 			  VDPASIM_QUEUE_MAX, false,
> > > > 			  (struct vring_desc *)(uintptr_t)vq->desc_addr,
> > > > 			  (struct vring_avail *)
> > > > @@ -86,7 +86,7 @@ static void vdpasim_vq_reset(struct
vdpasim *vdpasim,
> > > > 	vq->device_addr = 0;
> > > > 	vq->cb = NULL;
> > > > 	vq->private = NULL;
> > > > -	vringh_init_iotlb(&vq->vring,
vdpasim->dev_attr.supported_features,
> > > > +	vringh_init_iotlb(&vq->vring, vdpasim->features,
> > > 
> > > vdpasim_vq_reset() is called while resetting the device in
vdpasim_reset()
> > > where we also set `vdpasim->features = 0` after resetting the
vqs, so maybe
> > > it's better to use the supported features here, since the
negotiated ones
> > > are related to the previous instance.
> > > 
> > 
> > I don't think using supported features is valid. Better to make
sure
> > vringh_init_iotlb() is called after the features have been negotiated.
> > 
> 
> I think the vringh_init_iotlb() call in vdpasim_vq_reset() is just used to
> clean up the `struct vringh`, then it will be initialized in
> vdpasim_queue_ready() when features have already been negotiated.
> 
> Maybe here we can pass 0 (to the features parameter) if we don't want
to use
> the features supported by the device.
> 
> Thanks,
> Stefano
Eli? Maybe you can describe what is the observed bug the patch
is trying to fix.

Thanks!

-- 
MST