Re: [PATCH Kernel v18 6/7] vfio iommu: Add migration capability to report supported features

[Kirti Wankhede]

On 5/7/2020 3:57 AM, Alex Williamson wrote:
> On Mon, 4 May 2020 21:28:58 +0530
> Kirti Wankhede <address@hidden> wrote:
>
> > Added migration capability in IOMMU info chain.
> > User application should check IOMMU info chain for migration capability
> > to use dirty page tracking feature provided by kernel module.
> >
> > Signed-off-by: Kirti Wankhede <address@hidden>
> > ---
> >   drivers/vfio/vfio_iommu_type1.c | 15 +++++++++++++++
> >   include/uapi/linux/vfio.h       | 14 ++++++++++++++
> >   2 files changed, 29 insertions(+)
> >
> > diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> > index 8b27faf1ec38..b38d278d7bff 100644
> > --- a/drivers/vfio/vfio_iommu_type1.c
> > +++ b/drivers/vfio/vfio_iommu_type1.c
> > @@ -2378,6 +2378,17 @@ static int vfio_iommu_iova_build_caps(struct vfio_iommu 
> > *iommu,
> >         return ret;
> >   }
> >   
> > +static int vfio_iommu_migration_build_caps(struct vfio_info_cap *caps)
> > +{
> > +       struct vfio_iommu_type1_info_cap_migration cap_mig;
> > +
> > +       cap_mig.header.id = VFIO_IOMMU_TYPE1_INFO_CAP_MIGRATION;
> > +       cap_mig.header.version = 1;
> > +       cap_mig.flags = VFIO_IOMMU_INFO_CAPS_MIGRATION_DIRTY_PAGE_TRACK;
> > +
> > +       return vfio_info_add_capability(caps, &cap_mig.header, sizeof(cap_mig));
> > +}
> > +
> >   static long vfio_iommu_type1_ioctl(void *iommu_data,
> >                                    unsigned int cmd, unsigned long arg)
> >   {
> > @@ -2427,6 +2438,10 @@ static long vfio_iommu_type1_ioctl(void *iommu_data,
> >                 if (ret)
> >                         return ret;
> >   
> > +		ret = vfio_iommu_migration_build_caps(&caps);
> > +               if (ret)
> > +                       return ret;
> > +
> >                 if (caps.size) {
> >                         info.flags |= VFIO_IOMMU_INFO_CAPS;
> >   
> > diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> > index e3cbf8b78623..df9ce8aaafab 100644
> > --- a/include/uapi/linux/vfio.h
> > +++ b/include/uapi/linux/vfio.h
> > @@ -1013,6 +1013,20 @@ struct vfio_iommu_type1_info_cap_iova_range {
> >         struct  vfio_iova_range iova_ranges[];
> >   };
> >   
> > +/*
> > + * The migration capability allows to report supported features for migration.
> > + *
> > + * The structures below define version 1 of this capability.
> > + */
> > +#define VFIO_IOMMU_TYPE1_INFO_CAP_MIGRATION  1
> > +
> > +struct vfio_iommu_type1_info_cap_migration {
> > +       struct  vfio_info_cap_header header;
> > +       __u32   flags;
> > +       /* supports dirty page tracking */
> > +#define VFIO_IOMMU_INFO_CAPS_MIGRATION_DIRTY_PAGE_TRACK        (1 << 0)
> > +};
> > +
>
> What about exposing the maximum supported dirty bitmap size and the
> supported page sizes?  Thanks,

How should user application use that?

Thanks,
Kirti

> Alex
>
> >   #define VFIO_IOMMU_GET_INFO _IO(VFIO_TYPE, VFIO_BASE + 12)
> >   
> >   /**