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

[David Gibson]

On Tue, May 14, 2013 at 11:15:26AM -0600, Alex Williamson wrote:
> On Tue, 2013-05-14 at 19:13 +1000, David Gibson wrote:
> > 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 <address@hidden>
> > ---
> >  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;
> 
> Seems like this would be related to the space, not the container.

So, originally I was going to put it into the space, until I realised
that the MemoryListener which sets it up is already per-container.
The list still could be per-space, of course, but we'd have to do a
bunch of check-if-it's-already there stuff.  And the remove path is
worse.

> >      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);
> > +
> > +    if (iotlb->perm[0] || iotlb->perm[1]) {
> > +        ret = vfio_dma_map(container, iotlb->iova,
> > +                           iotlb->addr_mask + 1, vaddr,
> > +                           !iotlb->perm[1] || mrs->readonly);
> > +        if (ret) {
> > +            error_report("vfio_dma_map(%p, 0x%"HWADDR_PRIx", "
> > +                         "0x%"HWADDR_PRIx", %p) = %d (%m)",
> > +                         container, iotlb->iova,
> > +                         iotlb->addr_mask + 1, vaddr, ret);
> > +        }
> > +    } else {
> > +        ret = vfio_dma_unmap(container, iotlb->iova, iotlb->addr_mask + 1);
> > +        if (ret) {
> > +            error_report("vfio_dma_unmap(%p, 0x%"HWADDR_PRIx", "
> > +                         "0x%"HWADDR_PRIx") = %d (%m)",
> > +                         container, iotlb->iova,
> > +                         iotlb->addr_mask + 1, ret);
> > +        }
> > +    }
> >  }
> >  
> >  static void vfio_listener_region_add(MemoryListener *listener,
> > @@ -1949,11 +2014,8 @@ static void vfio_listener_region_add(MemoryListener 
> > *listener,
> >      VFIOContainer *container = container_of(listener, VFIOContainer,
> >                                              iommu_data.listener);
> >      hwaddr iova, end;
> > -    void *vaddr;
> >      int ret;
> >  
> > -    assert(!memory_region_is_iommu(section->mr));
> > -
> >      if (vfio_listener_skipped_section(section)) {
> >          DPRINTF("SKIPPING region_add %"HWADDR_PRIx" - %"PRIx64"\n",
> >                  section->offset_within_address_space,
> > @@ -1975,20 +2037,55 @@ static void vfio_listener_region_add(MemoryListener 
> > *listener,
> >          return;
> >      }
> >  
> > -    vaddr = memory_region_get_ram_ptr(section->mr) +
> > +    memory_region_ref(section->mr);
> > +
> > +    if (memory_region_is_ram(section->mr)) {
> > +        void *vaddr;
> > +
> > +        DPRINTF("region_add [ram] %"HWADDR_PRIx" - %"HWADDR_PRIx" [%p]\n",
> > +                iova, end - 1, vaddr);
> > +
> > +        vaddr = memory_region_get_ram_ptr(section->mr) +
> >              section->offset_within_region +
> >              (iova - section->offset_within_address_space);
> >  
> > -    DPRINTF("region_add %"HWADDR_PRIx" - %"HWADDR_PRIx" [%p]\n",
> > -            iova, end - 1, vaddr);
> >  
> > -    memory_region_ref(section->mr);
> > -    ret = vfio_dma_map(container, iova, end - iova, vaddr, 
> > section->readonly);
> > -    if (ret) {
> > -        error_report("vfio_dma_map(%p, 0x%"HWADDR_PRIx", "
> > -                     "0x%"HWADDR_PRIx", %p) = %d (%m)",
> > -                     container, iova, end - iova, vaddr, ret);
> > +        ret = vfio_dma_map(container, iova, end - iova, vaddr,
> > +                           section->readonly);
> > +        if (ret) {
> > +            error_report("vfio_dma_map(%p, 0x%"HWADDR_PRIx", "
> > +                         "0x%"HWADDR_PRIx", %p) = %d (%m)",
> > +                         container, iova, end - iova, vaddr, ret);
> > +        }
> > +    } else if (memory_region_is_iommu(section->mr)) {
> > +        VFIOGuestIOMMU *giommu;
> > +
> > +        DPRINTF("region_add [iommu] %"HWADDR_PRIx" - %"HWADDR_PRIx"\n",
> > +                iova, end - 1);
> > +
> > +        /*
> > +         * FIXME: We should do some checking to see if the
> > +         * capabilities of the host VFIO IOMMU are adequate to model
> > +         * the guest IOMMU
> > +         *
> > +         * FIXME: This assumes that the guest IOMMU is empty of
> > +         * mappings at this point - we should either enforce this, or
> > +         * loop through existing mappings to map them into VFIO.
> > +         *
> > +         * FIXME: For VFIO iommu types which have KVM acceleration to
> > +         * avoid bouncing all map/unmaps through qemu this way, this
> > +         * would be the right place to wire that up (tell the KVM
> > +         * device emulation the VFIO iommu handles to use).
> > +         */
> > +        giommu = g_malloc0(sizeof(*giommu));
> > +        giommu->iommu = section->mr;
> > +        giommu->container = container;
> > +        giommu->n.notify = vfio_iommu_map_notify;
> > +
> > +        QLIST_INSERT_HEAD(&container->guest_iommus, giommu, list);
> > +        memory_region_register_iommu_notifier(giommu->iommu, &giommu->n);
> 
> And this is also filtered on the space, so we're not adding iommus that
> aren't handling regions within this space, right?

I'm not sure what you're getting at.

> Does the memory listener need to move to the space?

That would make this simpler, but it has other problems.  Having the
listener per-container means that when a container is added to a space
which already has a bunch of things in it, we automatically get those
replayed by the listener so we can set up the new container.

And.. when we come to deal with the case of adding an iommu region
that already has a bunch of mappings, we may well want the iommu
notifier to be per-container for the same reason.

In some ways I'd prefer to add the iommu notifications as new
callbacks in the memorylistener, rather than a seperate set of
Notifiers, but to do that we'd need to iterate through all address
spaces that contain the iommu region, and I couldn't see a good way of
doing that.


> 
> >      }
> > +
> >  }
> >  
> >  static void vfio_listener_region_del(MemoryListener *listener,
> > @@ -2012,6 +2109,22 @@ static void vfio_listener_region_del(MemoryListener 
> > *listener,
> >          return;
> >      }
> >  
> > +    if (memory_region_is_iommu(section->mr)) {
> > +        VFIOGuestIOMMU *giommu;
> > +
> > +        QLIST_FOREACH(giommu, &container->guest_iommus, list) {
> > +            if (giommu->iommu == section->mr) {
> > +                memory_region_unregister_iommu_notifier(&giommu->n);
> 
> Missing free

Oops.  And list remove for that matter.  Fixing for next version.

-- 
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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