Re: [Qemu-devel] [PATCH v5 05/11] vfio: Introduce VFIO address spaces

[Alex Williamson]

On Wed, 2014-03-12 at 16:52 +1100, Alexey Kardashevskiy wrote:
> From: David Gibson <address@hidden>
> 
> The only model so far supported for VFIO passthrough devices is the model
> usually used on x86, where all of the guest's RAM is mapped into the
> (host) IOMMU and there is no IOMMU visible in the guest.
> 
> This patch begins to relax this model, introducing the notion of a
> VFIOAddressSpace.  This represents a logical DMA address space which will
> be visible to one or more VFIO devices by appropriate mapping in the (host)
> IOMMU.  Thus the currently global list of containers becomes local to
> a VFIOAddressSpace, and we verify that we don't attempt to add a VFIO
> group to multiple address spaces.
> 
> For now, only one VFIOAddressSpace is created and used, corresponding to
> main system memory, that will change in future patches.
> 
> Signed-off-by: David Gibson <address@hidden>
> Signed-off-by: Alexey Kardashevskiy <address@hidden>
> 
> ---
> Changes:
> v5:
> * vfio_get_group() now receives AddressSpace*
> 
> v4:
> * removed redundant checks and asserts
> * fixed some return error codes
> ---
>  hw/misc/vfio.c | 53 ++++++++++++++++++++++++++++++++++++++++-------------
>  1 file changed, 40 insertions(+), 13 deletions(-)
> 
> diff --git a/hw/misc/vfio.c b/hw/misc/vfio.c
> index 6a04c2a..c8236c3 100644
> --- a/hw/misc/vfio.c
> +++ b/hw/misc/vfio.c
> @@ -133,6 +133,22 @@ enum {
>      VFIO_INT_MSIX = 3,
>  };
>  
> +typedef struct VFIOAddressSpace {
> +    AddressSpace *as;
> +    QLIST_HEAD(, VFIOContainer) containers;
> +    QLIST_ENTRY(VFIOAddressSpace) list;
> +} VFIOAddressSpace;
> +
> +QLIST_HEAD(, VFIOAddressSpace) vfio_address_spaces;

Why isn't this static and initialized with QLIST_HEAD_INITIALIZER like
the qlist it replaces?

> +
> +static VFIOAddressSpace vfio_address_space_memory;
> +
> +static void vfio_address_space_init(VFIOAddressSpace *space, AddressSpace 
> *as)
> +{
> +    space->as = as;
> +    QLIST_INIT(&space->containers);
> +}
> +
>  struct VFIOGroup;
>  
>  typedef struct VFIOType1 {
> @@ -142,6 +158,7 @@ typedef struct VFIOType1 {
>  } VFIOType1;
>  
>  typedef struct VFIOContainer {
> +    VFIOAddressSpace *space;
>      int fd; /* /dev/vfio/vfio, empowered by the attached groups */
>      struct {
>          /* enable abstraction to support various iommu backends */
> @@ -234,9 +251,6 @@ static const VFIORomBlacklistEntry romblacklist[] = {
>  
>  #define MSIX_CAP_LENGTH 12
>  
> -static QLIST_HEAD(, VFIOContainer)
> -    container_list = QLIST_HEAD_INITIALIZER(container_list);
> -
>  static QLIST_HEAD(, VFIOGroup)
>      group_list = QLIST_HEAD_INITIALIZER(group_list);
>  
> @@ -3280,16 +3294,15 @@ static void vfio_kvm_device_del_group(VFIOGroup 
> *group)
>  #endif
>  }
>  
> -static int vfio_connect_container(VFIOGroup *group)
> +static int vfio_connect_container(VFIOGroup *group, AddressSpace *as)
>  {
>      VFIOContainer *container;
>      int ret, fd;
> +    VFIOAddressSpace *space;
>  
> -    if (group->container) {
> -        return 0;
> -    }
> +    space = &vfio_address_space_memory;
>  
> -    QLIST_FOREACH(container, &container_list, next) {
> +    QLIST_FOREACH(container, &space->containers, next) {
>          if (!ioctl(group->fd, VFIO_GROUP_SET_CONTAINER, &container->fd)) {
>              group->container = container;
>              QLIST_INSERT_HEAD(&container->group_list, group, container_next);
> @@ -3312,6 +3325,7 @@ static int vfio_connect_container(VFIOGroup *group)
>      }
>  
>      container = g_malloc0(sizeof(*container));
> +    container->space = space;
>      container->fd = fd;
>  
>      if (ioctl(fd, VFIO_CHECK_EXTENSION, VFIO_TYPE1_IOMMU)) {
> @@ -3349,7 +3363,7 @@ static int vfio_connect_container(VFIOGroup *group)
>      }
>  
>      QLIST_INIT(&container->group_list);
> -    QLIST_INSERT_HEAD(&container_list, container, next);
> +    QLIST_INSERT_HEAD(&space->containers, container, next);
>  
>      group->container = container;
>      QLIST_INSERT_HEAD(&container->group_list, group, container_next);
> @@ -3392,7 +3406,7 @@ static void vfio_disconnect_container(VFIOGroup *group)
>      }
>  }
>  
> -static VFIOGroup *vfio_get_group(int groupid)
> +static VFIOGroup *vfio_get_group(int groupid, AddressSpace *as)
>  {
>      VFIOGroup *group;
>      char path[32];
> @@ -3400,7 +3414,14 @@ static VFIOGroup *vfio_get_group(int groupid)
>  
>      QLIST_FOREACH(group, &group_list, next) {
>          if (group->groupid == groupid) {
> -            return group;
> +            /* Found it.  Now is it already in the right context? */
> +            if (group->container->space->as == as) {
> +                return group;
> +            } else {
> +                error_report("vfio: group %d used in multiple address 
> spaces",
> +                             group->groupid);
> +                return NULL;
> +            }
>          }
>      }
>  
> @@ -3428,7 +3449,7 @@ static VFIOGroup *vfio_get_group(int groupid)
>      group->groupid = groupid;
>      QLIST_INIT(&group->device_list);
>  
> -    if (vfio_connect_container(group)) {
> +    if (vfio_connect_container(group, as)) {
>          error_report("vfio: failed to setup container for group %d", 
> groupid);
>          goto close_fd_exit;
>      }
> @@ -3780,7 +3801,12 @@ static int vfio_initfn(PCIDevice *pdev)
>      DPRINTF("%s(%04x:%02x:%02x.%x) group %d\n", __func__, vdev->host.domain,
>              vdev->host.bus, vdev->host.slot, vdev->host.function, groupid);
>  
> -    group = vfio_get_group(groupid);
> +    if (pci_device_iommu_address_space(pdev) != &address_space_memory) {
> +        error_report("vfio: DMA address space must be system memory");
> +        return -EINVAL;
> +    }
> +
> +    group = vfio_get_group(groupid, &address_space_memory);
>      if (!group) {
>          error_report("vfio: failed to get group %d", groupid);
>          return -ENOENT;
> @@ -3994,6 +4020,7 @@ static const TypeInfo vfio_pci_dev_info = {
>  
>  static void register_vfio_pci_dev_type(void)
>  {
> +    vfio_address_space_init(&vfio_address_space_memory, 
> &address_space_memory);
>      type_register_static(&vfio_pci_dev_info);
>  }
>