Re: [PATCH v2 19/19] vdpasim: control virtqueue support

[Eugenio Perez Martin]

On Wed, Jun 22, 2022 at 12:21 PM Eugenio Perez Martin
<eperezma@xxxxxxxxxx> wrote:
>
> On Tue, Jun 21, 2022 at 5:20 PM Stefano Garzarella <sgarzare@xxxxxxxxxx> wrote:
> >
> > Hi Gautam,
> >
> > On Wed, Mar 30, 2022 at 8:21 PM Gautam Dawar <gautam.dawar@xxxxxxxxxx> wrote:
> > >
> > > This patch introduces the control virtqueue support for vDPA
> > > simulator. This is a requirement for supporting advanced features like
> > > multiqueue.
> > >
> > > A requirement for control virtqueue is to isolate its memory access
> > > from the rx/tx virtqueues. This is because when using vDPA device
> > > for VM, the control virqueue is not directly assigned to VM. Userspace
> > > (Qemu) will present a shadow control virtqueue to control for
> > > recording the device states.
> > >
> > > The isolation is done via the virtqueue groups and ASID support in
> > > vDPA through vhost-vdpa. The simulator is extended to have:
> > >
> > > 1) three virtqueues: RXVQ, TXVQ and CVQ (control virtqueue)
> > > 2) two virtqueue groups: group 0 contains RXVQ and TXVQ; group 1
> > >    contains CVQ
> > > 3) two address spaces and the simulator simply implements the address
> > >    spaces by mapping it 1:1 to IOTLB.
> > >
> > > For the VM use cases, userspace(Qemu) may set AS 0 to group 0 and AS 1
> > > to group 1. So we have:
> > >
> > > 1) The IOTLB for virtqueue group 0 contains the mappings of guest, so
> > >    RX and TX can be assigned to guest directly.
> > > 2) The IOTLB for virtqueue group 1 contains the mappings of CVQ which
> > >    is the buffers that allocated and managed by VMM only. So CVQ of
> > >    vhost-vdpa is visible to VMM only. And Guest can not access the CVQ
> > >    of vhost-vdpa.
> > >
> > > For the other use cases, since AS 0 is associated to all virtqueue
> > > groups by default. All virtqueues share the same mapping by default.
> > >
> > > To demonstrate the function, VIRITO_NET_F_CTRL_MACADDR is
> > > implemented in the simulator for the driver to set mac address.
> > >
> > > Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>
> > > Signed-off-by: Gautam Dawar <gdawar@xxxxxxxxxx>
> > > ---
> > >  drivers/vdpa/vdpa_sim/vdpa_sim.c     | 91 ++++++++++++++++++++++------
> > >  drivers/vdpa/vdpa_sim/vdpa_sim.h     |  2 +
> > >  drivers/vdpa/vdpa_sim/vdpa_sim_net.c | 88 ++++++++++++++++++++++++++-
> > >  3 files changed, 161 insertions(+), 20 deletions(-)
> > >
> > > diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.c b/drivers/vdpa/vdpa_sim/vdpa_sim.c
> > > index 659e2e2e4b0c..51bd0bafce06 100644
> > > --- a/drivers/vdpa/vdpa_sim/vdpa_sim.c
> > > +++ b/drivers/vdpa/vdpa_sim/vdpa_sim.c
> > > @@ -96,11 +96,17 @@ static void vdpasim_do_reset(struct vdpasim *vdpasim)
> > >  {
> > >         int i;
> > >
> > > -       for (i = 0; i < vdpasim->dev_attr.nvqs; i++)
> > > +       spin_lock(&vdpasim->iommu_lock);
> > > +
> > > +       for (i = 0; i < vdpasim->dev_attr.nvqs; i++) {
> > >                 vdpasim_vq_reset(vdpasim, &vdpasim->vqs[i]);
> > > +               vringh_set_iotlb(&vdpasim->vqs[i].vring, &vdpasim->iommu[0],
> > > +                                &vdpasim->iommu_lock);
> > > +       }
> > > +
> > > +       for (i = 0; i < vdpasim->dev_attr.nas; i++)
> > > +               vhost_iotlb_reset(&vdpasim->iommu[i]);
> > >
> > > -       spin_lock(&vdpasim->iommu_lock);
> > > -       vhost_iotlb_reset(vdpasim->iommu);
> > >         spin_unlock(&vdpasim->iommu_lock);
> > >
> > >         vdpasim->features = 0;
> > > @@ -145,7 +151,7 @@ static dma_addr_t vdpasim_map_range(struct vdpasim *vdpasim, phys_addr_t paddr,
> > >         dma_addr = iova_dma_addr(&vdpasim->iova, iova);
> > >
> > >         spin_lock(&vdpasim->iommu_lock);
> > > -       ret = vhost_iotlb_add_range(vdpasim->iommu, (u64)dma_addr,
> > > +       ret = vhost_iotlb_add_range(&vdpasim->iommu[0], (u64)dma_addr,
> > >                                     (u64)dma_addr + size - 1, (u64)paddr, perm);
> > >         spin_unlock(&vdpasim->iommu_lock);
> > >
> > > @@ -161,7 +167,7 @@ static void vdpasim_unmap_range(struct vdpasim *vdpasim, dma_addr_t dma_addr,
> > >                                 size_t size)
> > >  {
> > >         spin_lock(&vdpasim->iommu_lock);
> > > -       vhost_iotlb_del_range(vdpasim->iommu, (u64)dma_addr,
> > > +       vhost_iotlb_del_range(&vdpasim->iommu[0], (u64)dma_addr,
> > >                               (u64)dma_addr + size - 1);
> > >         spin_unlock(&vdpasim->iommu_lock);
> > >
> > > @@ -250,8 +256,9 @@ struct vdpasim *vdpasim_create(struct vdpasim_dev_attr *dev_attr)
> > >         else
> > >                 ops = &vdpasim_config_ops;
> > >
> > > -       vdpasim = vdpa_alloc_device(struct vdpasim, vdpa, NULL, ops, 1,
> > > -                                   1, dev_attr->name, false);
> > > +       vdpasim = vdpa_alloc_device(struct vdpasim, vdpa, NULL, ops,
> > > +                                   dev_attr->ngroups, dev_attr->nas,
> > > +                                   dev_attr->name, false);
> > >         if (IS_ERR(vdpasim)) {
> > >                 ret = PTR_ERR(vdpasim);
> > >                 goto err_alloc;
> > > @@ -278,16 +285,20 @@ struct vdpasim *vdpasim_create(struct vdpasim_dev_attr *dev_attr)
> > >         if (!vdpasim->vqs)
> > >                 goto err_iommu;
> > >
> > > -       vdpasim->iommu = vhost_iotlb_alloc(max_iotlb_entries, 0);
> > > +       vdpasim->iommu = kmalloc_array(vdpasim->dev_attr.nas,
> > > +                                      sizeof(*vdpasim->iommu), GFP_KERNEL);
> > >         if (!vdpasim->iommu)
> > >                 goto err_iommu;
> > >
> > > +       for (i = 0; i < vdpasim->dev_attr.nas; i++)
> > > +               vhost_iotlb_init(&vdpasim->iommu[i], 0, 0);
> > > +
> > >         vdpasim->buffer = kvmalloc(dev_attr->buffer_size, GFP_KERNEL);
> > >         if (!vdpasim->buffer)
> > >                 goto err_iommu;
> > >
> > >         for (i = 0; i < dev_attr->nvqs; i++)
> > > -               vringh_set_iotlb(&vdpasim->vqs[i].vring, vdpasim->iommu,
> > > +               vringh_set_iotlb(&vdpasim->vqs[i].vring, &vdpasim->iommu[0],
> > >                                  &vdpasim->iommu_lock);
> > >
> > >         ret = iova_cache_get();
> > > @@ -401,7 +412,11 @@ static u32 vdpasim_get_vq_align(struct vdpa_device *vdpa)
> > >
> > >  static u32 vdpasim_get_vq_group(struct vdpa_device *vdpa, u16 idx)
> > >  {
> > > -       return 0;
> > > +       /* RX and TX belongs to group 0, CVQ belongs to group 1 */
> > > +       if (idx == 2)
> > > +               return 1;
> > > +       else
> > > +               return 0;
> >
> > This code only works for the vDPA-net simulator, since
> > vdpasim_get_vq_group() is also shared with other simulators (e.g.
> > vdpa_sim_blk),
>
> That's totally right.
>
> > should we move this net-specific code into
> > vdpa_sim_net.c, maybe adding a callback implemented by the different
> > simulators?
> >
>
> At this moment, VDPASIM_BLK_VQ_NUM is fixed to 1, so maybe the right
> thing to do for the -rc phase is to check if idx > vdpasim.attr.nvqs?
> It's a more general fix.
>

Actually, that is already checked by vhost/vdpa.c.

Taking that into account, is it worth introducing the change for 5.19?
I'm totally ok with the change for 5.20.

Thanks!

> For the general case, yes, a callback should be issued to the actual
> simulator so it's not a surprise when VDPASIM_BLK_VQ_NUM increases,
> either dynamically or by anyone testing it.
>
> Thoughts?
>
> Thanks!