Re: [PATCH v8 4/8] virtio-iommu: set supported page size mask

[Bharat Bhushan]

Hi Eric/Jean,

On Wed, Mar 18, 2020 at 8:05 PM Bharat Bhushan <address@hidden> wrote:
>
> Hi Eric,
>
> On Wed, Mar 18, 2020 at 4:58 PM Auger Eric <address@hidden> wrote:
> >
> > Hi Bharat,
> >
> > On 3/18/20 11:11 AM, Bharat Bhushan wrote:
> > > Add optional interface to set page size mask.
> > > Currently this is set global configuration and not
> > > per endpoint.
> > >
> > > Signed-off-by: Bharat Bhushan <address@hidden>
> > > ---
> > > v7->v8:
> > >  - new patch
> > >
> > >  hw/virtio/virtio-iommu.c | 10 ++++++++++
> > >  1 file changed, 10 insertions(+)
> > >
> > > diff --git a/hw/virtio/virtio-iommu.c b/hw/virtio/virtio-iommu.c
> > > index 4cee8083bc..c00a55348d 100644
> > > --- a/hw/virtio/virtio-iommu.c
> > > +++ b/hw/virtio/virtio-iommu.c
> > > @@ -650,6 +650,15 @@ static gint int_cmp(gconstpointer a, gconstpointer 
> > > b, gpointer user_data)
> > >      return (ua > ub) - (ua < ub);
> > >  }
> > >
> > > +static void virtio_iommu_set_page_size_mask(IOMMUMemoryRegion *mr,
> > > +                                            uint64_t page_size_mask)
> > > +{
> > > +    IOMMUDevice *sdev = container_of(mr, IOMMUDevice, iommu_mr);
> > > +    VirtIOIOMMU *s = sdev->viommu;
> > > +
> > > +    s->config.page_size_mask = page_size_mask;
> > The problem is page_size_mask is global to the VIRTIO-IOMMU.
> >
> > - Can't different VFIO containers impose different/inconsistent settings?
> > - VFIO devices can be hotplugged.
>
> This is possible if we different iommu's, which we support. correct?
>
> > So we may start with some default
> > page_size_mask which is latter overriden by a host imposed one. Assume
> > you first launch the VM with a virtio NIC. This uses 64K. Then you
> > hotplug a VFIO device behind a physical IOMMU which only supports 4K
> > pages. Isn't it a valid scenario?
>
> So we need to expose page_size_mask per endpoint?

Just sent Linux RFC patch to use page-size-mask per endpoint.
QEMU changes are also ready, will share soon.

Thanks
-Bharat

>
> Thanks
> -Bharat
>
> >
> > Thanks
> >
> > Eric
> >
> > > +}
> > > +
> > >  static void virtio_iommu_device_realize(DeviceState *dev, Error **errp)
> > >  {
> > >      VirtIODevice *vdev = VIRTIO_DEVICE(dev);
> > > @@ -865,6 +874,7 @@ static void 
> > > virtio_iommu_memory_region_class_init(ObjectClass *klass,
> > >      IOMMUMemoryRegionClass *imrc = IOMMU_MEMORY_REGION_CLASS(klass);
> > >
> > >      imrc->translate = virtio_iommu_translate;
> > > +    imrc->iommu_set_page_size_mask = virtio_iommu_set_page_size_mask;
> > >  }
> > >
> > >  static const TypeInfo virtio_iommu_info = {
> > >
> >