Re: [Qemu-devel] [Qemu-ppc] [PATCH 11/11] vfio: Add guest side IOMMU support

[David Gibson <david@gibson.dropbear.id.au>]

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On Tue, May 14, 2013 at 11:48:47AM +0200, Paolo Bonzini wrote:
> Il 14/05/2013 11:13, David Gibson ha scritto:
> > This patch uses the new IOMMU notifiers to allow VFIO pass through devices
> > to work with guest side IOMMUs, as long as the host-side VFIO iommu has
> > sufficient capability and granularity to match the guest side. This works
> > by tracking all map and unmap operations on the guest IOMMU using the
> > notifiers, and mirroring them into VFIO.
> > 
> > There are a number of FIXMEs, and the scheme involves rather more notifier
> > structures than I'd like, but it shuold make for a reasonable proof of
> > concept.
> > 
> > Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> > ---
> >  hw/misc/vfio.c |  139 ++++++++++++++++++++++++++++++++++++++++++++++++++------
> >  1 file changed, 126 insertions(+), 13 deletions(-)
> > 
> > diff --git a/hw/misc/vfio.c b/hw/misc/vfio.c
> > index f4e3792..62a83ca 100644
> > --- a/hw/misc/vfio.c
> > +++ b/hw/misc/vfio.c
> > @@ -133,10 +133,18 @@ typedef struct VFIOContainer {
> >          };
> >          void (*release)(struct VFIOContainer *);
> >      } iommu_data;
> > +    QLIST_HEAD(, VFIOGuestIOMMU) guest_iommus;
> >      QLIST_HEAD(, VFIOGroup) group_list;
> >      QLIST_ENTRY(VFIOContainer) next;
> >  } VFIOContainer;
> >  
> > +typedef struct VFIOGuestIOMMU {
> > +    VFIOContainer *container;
> > +    MemoryRegion *iommu;
> > +    Notifier n;
> > +    QLIST_ENTRY(VFIOGuestIOMMU) list;
> > +} VFIOGuestIOMMU;
> > +
> >  /* Cache of MSI-X setup plus extra mmap and memory region for split BAR map */
> >  typedef struct VFIOMSIXInfo {
> >      uint8_t table_bar;
> > @@ -1940,7 +1948,64 @@ static int vfio_dma_map(VFIOContainer *container, hwaddr iova,
> >  
> >  static bool vfio_listener_skipped_section(MemoryRegionSection *section)
> >  {
> > -    return !memory_region_is_ram(section->mr);
> > +    return !memory_region_is_ram(section->mr) &&
> > +        !memory_region_is_iommu(section->mr);
> > +}
> > +
> > +static void vfio_iommu_map_notify(Notifier *n, void *data)
> > +{
> > +    VFIOGuestIOMMU *giommu = container_of(n, VFIOGuestIOMMU, n);
> > +    MemoryRegion *iommu = giommu->iommu;
> > +    VFIOContainer *container = giommu->container;
> > +    IOMMUTLBEntry *iotlb = data;
> > +    MemoryRegionSection *mrs;
> > +    hwaddr xlat;
> > +    hwaddr len = iotlb->addr_mask + 1;
> > +    void *vaddr;
> > +    int ret;
> > +
> > +    DPRINTF("iommu map @ %"HWADDR_PRIx" - %"HWADDR_PRIx"\n",
> > +            iotlb->iova, iotlb->iova + iotlb->address_mask);
> > +
> > +    /* The IOMMU TLB entry we have just covers translation through
> > +     * this IOMMU to its immediate target.  We need to translate
> > +     * it the rest of the way through to memory. */
> > +    mrs = address_space_translate(iommu->iommu_target_as,
> > +                                  iotlb->translated_addr,
> > +                                  &xlat, &len, iotlb->perm[1]);
> > +    if (!memory_region_is_ram(mrs->mr)) {
> > +        DPRINTF("iommu map to non memory area %"HWADDR_PRIx"\n",
> > +                xlat);
> > +        return;
> > +    }
> > +    if (len & iotlb->addr_mask) {
> > +        DPRINTF("iommu has granularity incompatible with target AS\n");
> > +        return;
> > +    }
> > +
> > +    vaddr = memory_region_get_ram_ptr(mrs->mr) +
> > +        mrs->offset_within_region +
> > +        (xlat - mrs->offset_within_address_space);
> 
> Are you sure you need this translation?  It's done already in
> address_space_translate, so it should be just
> 
> vaddr = memory_region_get_ram_ptr(mrs->mr) + xlat;

Ah, yes.  I wasn't sure what xlat was relative to (the final address
space, or the final memory region).  Looking more carefully at the
similar path in address_space_map(), I see that it's the memory
region.  I'll fix that up.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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