Re: [PATCH v4 12/15] vfio/common: Support device dirty page tracking with vIOMMU

[Duan, Zhenzhong]

On 9/8/2023 6:11 PM, Joao Martins wrote:
> On 08/09/2023 07:11, Duan, Zhenzhong wrote:
> > Hi Joao,
> >
> > On 6/23/2023 5:48 AM, Joao Martins wrote:
> > > Currently, device dirty page tracking with vIOMMU is not supported,
> > > and a blocker is added and the migration is prevented.
> > >
> > > When vIOMMU is used, IOVA ranges are DMA mapped/unmapped on the fly as
> > > requesting by the vIOMMU. These IOVA ranges can potentially be mapped
> > > anywhere in the vIOMMU IOVA space as advertised by the VMM.
> > >
> > > To support device dirty tracking when vIOMMU enabled instead create the
> > > dirty ranges based on the vIOMMU provided limits, which leads to the
> > > tracking of the whole IOVA space regardless of what devices use.
> > >
> > > Signed-off-by: Avihai Horon <avihaih@nvidia.com>
> > > Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
> > > ---
> > >    include/hw/vfio/vfio-common.h |  1 +
> > >    hw/vfio/common.c              | 58 +++++++++++++++++++++++++++++------
> > >    hw/vfio/pci.c                 |  7 +++++
> > >    3 files changed, 56 insertions(+), 10 deletions(-)
> > >
> > > diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h
> > > index f41860988d6b..c4bafad084b4 100644
> > > --- a/include/hw/vfio/vfio-common.h
> > > +++ b/include/hw/vfio/vfio-common.h
> > > @@ -71,6 +71,7 @@ typedef struct VFIOMigration {
> > >    typedef struct VFIOAddressSpace {
> > >        AddressSpace *as;
> > >        bool no_dma_translation;
> > > +    hwaddr max_iova;
> > >        QLIST_HEAD(, VFIOContainer) containers;
> > >        QLIST_ENTRY(VFIOAddressSpace) list;
> > >    } VFIOAddressSpace;
> > > diff --git a/hw/vfio/common.c b/hw/vfio/common.c
> > > index ecfb9afb3fb6..85fddef24026 100644
> > > --- a/hw/vfio/common.c
> > > +++ b/hw/vfio/common.c
> > > @@ -428,6 +428,25 @@ static bool vfio_viommu_preset(void)
> > >        return false;
> > >    }
> > >    +static int vfio_viommu_get_max_iova(hwaddr *max_iova)
> > > +{
> > > +    VFIOAddressSpace *space;
> > > +
> > > +    *max_iova = 0;
> > > +
> > > +    QLIST_FOREACH(space, &vfio_address_spaces, list) {
> > > +        if (space->as == &address_space_memory) {
> > > +            continue;
> > > +        }
> > Just curious why address_space_memory is bypassed?
> But address_space_memory part is done by memory listeners

Only this part. Still think about the case with two vfio devices, one 
bypass iommu, the other not.

The device bypassing iommu will get address_space_memory, the other get 
iommu

address space. vfio_viommu_preset() return true for any device, so we 
never run into

memory listener even for device bypassing iommu?


Thanks

Zhenzhong