Re: [PATCH v2 06/12] vfio/pci: Introduce vfio_[attach/detach]_device

[Eric Auger]

Hi Zhenzhong,

On 9/26/23 13:32, Zhenzhong Duan wrote:
> From: Eric Auger <eric.auger@redhat.com>
>
> We want the VFIO devices to be able to use two different
> IOMMU backends, the legacy VFIO one and the new iommufd one.
>
> Introduce vfio_[attach/detach]_device which aim at hiding the
> underlying IOMMU backend (IOCTLs, datatypes, ...).
>
> Once vfio_attach_device completes, the device is attached
> to a security context and its fd can be used. Conversely
> When vfio_detach_device completes, the device has been
> detached from the security context.
>
> At the moment only the implementation based on the legacy
> container/group exists. Let's use it from the vfio-pci device.
> Subsequent patches will handle other devices.
>
> Signed-off-by: Eric Auger <eric.auger@redhat.com>
> Signed-off-by: Yi Liu <yi.l.liu@intel.com>
> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
> ---
>  include/hw/vfio/vfio-common.h |  3 ++
>  hw/vfio/common.c              | 68 +++++++++++++++++++++++++++++++++++
>  hw/vfio/pci.c                 | 50 +++-----------------------
>  hw/vfio/trace-events          |  2 +-
>  4 files changed, 77 insertions(+), 46 deletions(-)
>
> diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h
> index c4e7c3b4a7..12fbfbc37d 100644
> --- a/include/hw/vfio/vfio-common.h
> +++ b/include/hw/vfio/vfio-common.h
> @@ -225,6 +225,9 @@ void vfio_put_group(VFIOGroup *group);
>  struct vfio_device_info *vfio_get_device_info(int fd);
>  int vfio_get_device(VFIOGroup *group, const char *name,
>                      VFIODevice *vbasedev, Error **errp);
> +int vfio_attach_device(char *name, VFIODevice *vbasedev,
> +                       AddressSpace *as, Error **errp);
> +void vfio_detach_device(VFIODevice *vbasedev);
>  
>  int vfio_kvm_device_add_fd(int fd, Error **errp);
>  int vfio_kvm_device_del_fd(int fd, Error **errp);
> diff --git a/hw/vfio/common.c b/hw/vfio/common.c
> index 959b1362bb..7f3798b152 100644
> --- a/hw/vfio/common.c
> +++ b/hw/vfio/common.c
> @@ -2611,3 +2611,71 @@ int vfio_eeh_as_op(AddressSpace *as, uint32_t op)
>      }
>      return vfio_eeh_container_op(container, op);
>  }
> +
> +static int vfio_device_groupid(VFIODevice *vbasedev, Error **errp)
> +{
> +    char *tmp, group_path[PATH_MAX], *group_name;
> +    int ret, groupid;
> +    ssize_t len;
> +
> +    tmp = g_strdup_printf("%s/iommu_group", vbasedev->sysfsdev);
> +    len = readlink(tmp, group_path, sizeof(group_path));
> +    g_free(tmp);
> +
> +    if (len <= 0 || len >= sizeof(group_path)) {
> +        ret = len < 0 ? -errno : -ENAMETOOLONG;
> +        error_setg_errno(errp, -ret, "no iommu_group found");
> +        return ret;
> +    }
> +
> +    group_path[len] = 0;
> +
> +    group_name = basename(group_path);
> +    if (sscanf(group_name, "%d", &groupid) != 1) {
> +        error_setg_errno(errp, errno, "failed to read %s", group_path);
> +        return -errno;
> +    }
> +    return groupid;
> +}
> +
> +int vfio_attach_device(char *name, VFIODevice *vbasedev,
> +                       AddressSpace *as, Error **errp)
> +{
> +    int groupid = vfio_device_groupid(vbasedev, errp);
> +    VFIODevice *vbasedev_iter;
> +    VFIOGroup *group;
> +    int ret;
> +
> +    if (groupid < 0) {
> +        return groupid;
> +    }
> +
> +    trace_vfio_attach_device(vbasedev->name, groupid);
> +
> +    group = vfio_get_group(groupid, as, errp);
> +    if (!group) {
> +        return -ENOENT;
> +    }
> +
> +    QLIST_FOREACH(vbasedev_iter, &group->device_list, next) {
> +        if (strcmp(vbasedev_iter->name, vbasedev->name) == 0) {
> +            error_setg(errp, "device is already attached");
> +            vfio_put_group(group);
> +            return -EBUSY;
> +        }
> +    }
> +    ret = vfio_get_device(group, name, vbasedev, errp);
> +    if (ret) {
> +        vfio_put_group(group);
> +    }
> +
> +    return ret;
> +}
> +
> +void vfio_detach_device(VFIODevice *vbasedev)
> +{
> +    VFIOGroup *group = vbasedev->group;
> +
> +    vfio_put_base_device(vbasedev);
> +    vfio_put_group(group);
> +}
> diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
> index 3b2ca3c24c..fe56789893 100644
> --- a/hw/vfio/pci.c
> +++ b/hw/vfio/pci.c
> @@ -2828,10 +2828,10 @@ static void vfio_populate_device(VFIOPCIDevice *vdev, 
> Error **errp)
>  
>  static void vfio_put_device(VFIOPCIDevice *vdev)
>  {
> +    vfio_detach_device(&vdev->vbasedev);
> +
>      g_free(vdev->vbasedev.name);
>      g_free(vdev->msix);
> -
> -    vfio_put_base_device(&vdev->vbasedev);
>  }
>  
>  static void vfio_err_notifier_handler(void *opaque)
> @@ -2978,13 +2978,9 @@ static void vfio_realize(PCIDevice *pdev, Error **errp)
>  {
>      VFIOPCIDevice *vdev = VFIO_PCI(pdev);
>      VFIODevice *vbasedev = &vdev->vbasedev;
> -    VFIODevice *vbasedev_iter;
> -    VFIOGroup *group;
> -    char *tmp, *subsys, group_path[PATH_MAX], *group_name;
> +    char *tmp, *subsys;
>      Error *err = NULL;
> -    ssize_t len;
>      struct stat st;
> -    int groupid;
>      int i, ret;
>      bool is_mdev;
>      char uuid[UUID_FMT_LEN];
> @@ -3015,39 +3011,6 @@ static void vfio_realize(PCIDevice *pdev, Error **errp)
>      vbasedev->type = VFIO_DEVICE_TYPE_PCI;
>      vbasedev->dev = DEVICE(vdev);
>  
> -    tmp = g_strdup_printf("%s/iommu_group", vbasedev->sysfsdev);
> -    len = readlink(tmp, group_path, sizeof(group_path));
> -    g_free(tmp);
> -
> -    if (len <= 0 || len >= sizeof(group_path)) {
> -        error_setg_errno(errp, len < 0 ? errno : ENAMETOOLONG,
> -                         "no iommu_group found");
> -        goto error;
> -    }
> -
> -    group_path[len] = 0;
> -
> -    group_name = basename(group_path);
> -    if (sscanf(group_name, "%d", &groupid) != 1) {
> -        error_setg_errno(errp, errno, "failed to read %s", group_path);
> -        goto error;
> -    }
> -
> -    trace_vfio_realize(vbasedev->name, groupid);
> -
> -    group = vfio_get_group(groupid, pci_device_iommu_address_space(pdev), 
> errp);
> -    if (!group) {
> -        goto error;
> -    }
> -
> -    QLIST_FOREACH(vbasedev_iter, &group->device_list, next) {
> -        if (strcmp(vbasedev_iter->name, vbasedev->name) == 0) {
> -            error_setg(errp, "device is already attached");
> -            vfio_put_group(group);
> -            goto error;
> -        }
> -    }
> -
>      /*
>       * Mediated devices *might* operate compatibly with discarding of RAM, 
> but
>       * we cannot know for certain, it depends on whether the mdev vendor 
> driver
> @@ -3065,7 +3028,6 @@ static void vfio_realize(PCIDevice *pdev, Error **errp)
>      if (vbasedev->ram_block_discard_allowed && !is_mdev) {
>          error_setg(errp, "x-balloon-allowed only potentially compatible "
>                     "with mdev devices");
> -        vfio_put_group(group);
>          goto error;
>      }
>  
> @@ -3076,10 +3038,10 @@ static void vfio_realize(PCIDevice *pdev, Error 
> **errp)
>          name = g_strdup(vbasedev->name);
>      }
>  
> -    ret = vfio_get_device(group, name, vbasedev, errp);
> +    ret = vfio_attach_device(name, vbasedev,
> +                             pci_device_iommu_address_space(pdev), errp);
>      g_free(name);
>      if (ret) {
> -        vfio_put_group(group);
independently on this patch, I think in case of error we leak
vbasedev->name. Please have a look and if confirmed you can send a
separate patch.

Also I think if any subsequent action fail we shoudl properly detach the
detach the device so introduce an extra error goto label, my bad sorry.

Thanks

Eric
>          goto error;
>      }
>  
> @@ -3304,7 +3266,6 @@ error:
>  static void vfio_instance_finalize(Object *obj)
>  {
>      VFIOPCIDevice *vdev = VFIO_PCI(obj);
> -    VFIOGroup *group = vdev->vbasedev.group;
>  
>      vfio_display_finalize(vdev);
>      vfio_bars_finalize(vdev);
> @@ -3318,7 +3279,6 @@ static void vfio_instance_finalize(Object *obj)
>       * g_free(vdev->igd_opregion);
>       */
>      vfio_put_device(vdev);
> -    vfio_put_group(group);
>  }
>  
>  static void vfio_exitfn(PCIDevice *pdev)
> diff --git a/hw/vfio/trace-events b/hw/vfio/trace-events
> index e64ca4a019..e710026a73 100644
> --- a/hw/vfio/trace-events
> +++ b/hw/vfio/trace-events
> @@ -37,7 +37,7 @@ vfio_pci_hot_reset_dep_devices(int domain, int bus, int 
> slot, int function, int
>  vfio_pci_hot_reset_result(const char *name, const char *result) "%s hot 
> reset: %s"
>  vfio_populate_device_config(const char *name, unsigned long size, unsigned 
> long offset, unsigned long flags) "Device %s config:\n  size: 0x%lx, offset: 
> 0x%lx, flags: 0x%lx"
>  vfio_populate_device_get_irq_info_failure(const char *errstr) 
> "VFIO_DEVICE_GET_IRQ_INFO failure: %s"
> -vfio_realize(const char *name, int group_id) " (%s) group %d"
> +vfio_attach_device(const char *name, int group_id) " (%s) group %d"
>  vfio_mdev(const char *name, bool is_mdev) " (%s) is_mdev %d"
>  vfio_add_ext_cap_dropped(const char *name, uint16_t cap, uint16_t offset) 
> "%s 0x%x@0x%x"
>  vfio_pci_reset(const char *name) " (%s)"