RE: [PATCH] vp_vdpa: Check queue number of vdpa device from add_config

[Angus Chen]

Hi,Jason.

> -----Original Message-----
> From: Jason Wang <jasowang@xxxxxxxxxx>
> Sent: Monday, June 5, 2023 2:54 PM
> To: Angus Chen <angus.chen@xxxxxxxxxxxxxxx>
> Cc: mst@xxxxxxxxxx; virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx;
> linux-kernel@xxxxxxxxxxxxxxx
> Subject: Re: [PATCH] vp_vdpa: Check queue number of vdpa device from
> add_config
> 
> On Fri, Jun 2, 2023 at 3:35 PM Angus Chen <angus.chen@xxxxxxxxxxxxxxx>
> wrote:
> >
> > When add virtio_pci vdpa device,check the vqs number of device cap
> > and max_vq_pairs from add_config.
> >
> > Signed-off-by: Angus Chen <angus.chen@xxxxxxxxxxxxxxx>
> > ---
> >  drivers/vdpa/virtio_pci/vp_vdpa.c | 11 +++++++++--
> >  1 file changed, 9 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/vdpa/virtio_pci/vp_vdpa.c
> b/drivers/vdpa/virtio_pci/vp_vdpa.c
> > index 281287fae89f..4bf1ab637d32 100644
> > --- a/drivers/vdpa/virtio_pci/vp_vdpa.c
> > +++ b/drivers/vdpa/virtio_pci/vp_vdpa.c
> > @@ -478,7 +478,7 @@ static int vp_vdpa_dev_add(struct vdpa_mgmt_dev
> *v_mdev, const char *name,
> >         struct device *dev = &pdev->dev;
> >         struct vp_vdpa *vp_vdpa = NULL;
> >         u64 device_features;
> > -       int ret, i;
> > +       int ret, i, queues;
> >
> >         vp_vdpa = vdpa_alloc_device(struct vp_vdpa, vdpa,
> >                                     dev, &vp_vdpa_ops, 1, 1, name,
> false);
> > @@ -491,7 +491,14 @@ static int vp_vdpa_dev_add(struct vdpa_mgmt_dev
> *v_mdev, const char *name,
> >         vp_vdpa_mgtdev->vp_vdpa = vp_vdpa;
> >
> >         vp_vdpa->vdpa.dma_dev = &pdev->dev;
> > -       vp_vdpa->queues = vp_modern_get_num_queues(mdev);
> > +       queues = vp_modern_get_num_queues(mdev);
> > +       if (add_config->mask &
> BIT_ULL(VDPA_ATTR_DEV_NET_CFG_MAX_VQP)) {
> > +               if (add_config->net.max_vq_pairs > queues / 2)
> > +                       return -EINVAL;
> > +               queues = min_t(u32, queues, 2 *
> add_config->net.max_vq_pairs);
> 
> Looks like you want to mediate the max_vqp here, but what happens:
> 
> 1) harware have 4 queue paris
> 2) vp_vdpa cap it into 2 queue pairs
> 3) guest may still try to enable 4 queue paris
> 
Yes，you are right，this situation can occur.
> For 3), the kernel needs to mediate the control virtqueue which seems not
> easy.
> 
> How about simply starting from failing if the provisioned #qp is not
> equal to the one that hardware has?
Ok,You mean we just check it in vp_vdpa or check it in all other vdpa net drivers?
> 
> Thanks
> 
> > +       }
> > +
> > +       vp_vdpa->queues = queues;
> >         vp_vdpa->mdev = mdev;
> >
> >         device_features = vp_modern_get_features(mdev);
> > --
> > 2.25.1
> >