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

[Alex Williamson]

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.

>      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?

Does the memory listener need to move to the space?

>      }
> +
>  }
>  
>  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

> +                break;
> +            }
> +        }
> +
> +        /* FIXME: We assume the one big unmap below is adequate to
> +         * remove any individual page mappings in the IOMMU which
> +         * might have been copied into VFIO.  That may not be true for
> +         * all IOMMU types */
> +    }
> +
>      iova = TARGET_PAGE_ALIGN(section->offset_within_address_space);
>      end = (section->offset_within_address_space + section->size) &
>            TARGET_PAGE_MASK;