RE: [EXT] Re: [PATCH v9 2/9] memory: Add interface to set iommu page size mask

[Bharat Bhushan]

Hi Eric,

> -----Original Message-----
> From: Auger Eric <address@hidden>
> Sent: Thursday, March 26, 2020 9:36 PM
> To: Bharat Bhushan <address@hidden>; address@hidden;
> address@hidden; address@hidden; address@hidden;
> address@hidden; address@hidden; Tomasz Nowicki [C]
> <address@hidden>; address@hidden; address@hidden; qemu-
> address@hidden; address@hidden; address@hidden; jean-
> address@hidden; address@hidden
> Subject: [EXT] Re: [PATCH v9 2/9] memory: Add interface to set iommu page size
> mask
> 
> External Email
> 
> ----------------------------------------------------------------------
> Hi Bharat,
> On 3/23/20 9:46 AM, Bharat Bhushan wrote:
> > Allow to set page size mask to be supported by iommu.
> by iommu memory region. I mean this is not global to the IOMMU.

Yes.

> > This is required to expose page size mask compatible with host with
> > virtio-iommu.
> >
> > Signed-off-by: Bharat Bhushan <address@hidden>
> > ---
> >  include/exec/memory.h | 20 ++++++++++++++++++++
> >  memory.c              | 10 ++++++++++
> >  2 files changed, 30 insertions(+)
> >
> > diff --git a/include/exec/memory.h b/include/exec/memory.h index
> > e85b7de99a..063c424854 100644
> > --- a/include/exec/memory.h
> > +++ b/include/exec/memory.h
> > @@ -355,6 +355,16 @@ typedef struct IOMMUMemoryRegionClass {
> >       * @iommu: the IOMMUMemoryRegion
> >       */
> >      int (*num_indexes)(IOMMUMemoryRegion *iommu);
> > +
> > +    /*
> > +     * Set supported IOMMU page size
> > +     *
> > +     * Optional method: if this is supported then set page size that
> > +     * can be supported by IOMMU. This is called to set supported page
> > +     * size as per host Linux.
> What about: If supported, allows to restrict the page size mask that can be
> supported with a given IOMMU memory region. For example, this allows to
> propagate host physical IOMMU page size mask limitations to the virtual IOMMU
> (vfio assignment with virtual iommu).

Much better 

> > +     */
> > +     void (*iommu_set_page_size_mask)(IOMMUMemoryRegion *iommu,
> > +                                      uint64_t page_size_mask);
> >  } IOMMUMemoryRegionClass;
> >
> >  typedef struct CoalescedMemoryRange CoalescedMemoryRange; @@ -1363,6
> > +1373,16 @@ int
> memory_region_iommu_attrs_to_index(IOMMUMemoryRegion *iommu_mr,
> >   */
> >  int memory_region_iommu_num_indexes(IOMMUMemoryRegion *iommu_mr);
> >
> > +/**
> > + * memory_region_iommu_set_page_size_mask: set the supported pages
> > + * size by iommu.
> supported page sizes for a given IOMMU memory region
> > + *
> > + * @iommu_mr: the memory region
> IOMMU memory region
> > + * @page_size_mask: supported page size mask  */ void
> > +memory_region_iommu_set_page_size_mask(IOMMUMemoryRegion
> *iommu_mr,
> > +                                            uint64_t page_size_mask);
> > +
> >  /**
> >   * memory_region_name: get a memory region's name
> >   *
> > diff --git a/memory.c b/memory.c
> > index aeaa8dcc9e..14c8783084 100644
> > --- a/memory.c
> > +++ b/memory.c
> > @@ -1833,6 +1833,16 @@ static int
> memory_region_update_iommu_notify_flags(IOMMUMemoryRegion
> *iommu_mr,
> >      return ret;
> >  }
> >
> > +void memory_region_iommu_set_page_size_mask(IOMMUMemoryRegion
> *iommu_mr,
> > +                                            uint64_t page_size_mask)
> > +{
> > +    IOMMUMemoryRegionClass *imrc =
> > +IOMMU_MEMORY_REGION_GET_CLASS(iommu_mr);
> > +
> > +    if (imrc->iommu_set_page_size_mask) {
> > +        imrc->iommu_set_page_size_mask(iommu_mr, page_size_mask);
> Shouldn't it return an int in case the setting cannot be applied?

iommu_set_page_size_mask() is setting page-size-mask for endpoint. Below 
function from code

        static void virtio_iommu_set_page_size_mask(IOMMUMemoryRegion *mr,
                                              uint64_t page_size_mask)
        {
                IOMMUDevice *sdev = container_of(mr, IOMMUDevice, iommu_mr);

                      sdev->page_size_mask = page_size_mask;
        }

Do you see any reason it cannot be applied, am I missing something?

Thanks
-Bharat

> > +    }
> > +}
> > +
> >  int memory_region_register_iommu_notifier(MemoryRegion *mr,
> >                                            IOMMUNotifier *n, Error
> > **errp)  {
> >
> Thanks
> Eric