Re: [PATCH V3 38/42] vfio/iommufd: reconstruct hw_caps

[Steven Sistare <steven.sistare@oracle.com>]

I withdraw this patch.  I will instead save devid in cpr-state.

- Steve

On 5/12/2025 11:32 AM, Steve Sistare wrote:
> hw_caps is normally derived during realize, at
> vfio_device_hiod_create_and_realize -> hiod_iommufd_vfio_realize ->
> iommufd_backend_get_device_info.  However, this depends on the devid, which
> is not preserved during CPR.
> 
> Save devid in vmstate.  Defer the vfio_device_hiod_create_and_realize call
> to post_load time, after devid has been recovered from vmstate.
> 
> Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
> ---
>   hw/vfio/cpr-iommufd.c  | 15 +++++++++++++++
>   hw/vfio/iommufd.c      |  6 ++----
>   hw/vfio/vfio-iommufd.h |  3 +++
>   3 files changed, 20 insertions(+), 4 deletions(-)
> 
> diff --git a/hw/vfio/cpr-iommufd.c b/hw/vfio/cpr-iommufd.c
> index 3d430f0..24cdf10 100644
> --- a/hw/vfio/cpr-iommufd.c
> +++ b/hw/vfio/cpr-iommufd.c
> @@ -100,12 +100,27 @@ void vfio_iommufd_cpr_unregister_container(VFIOIOMMUFDContainer *container)
>       migration_remove_notifier(&bcontainer->cpr_reboot_notifier);
>   }
>   
> +static int vfio_device_post_load(void *opaque, int version_id)
> +{
> +    VFIODevice *vbasedev = opaque;
> +    Error *err = NULL;
> +
> +    if (!vfio_device_hiod_create_and_realize(vbasedev,
> +                     TYPE_HOST_IOMMU_DEVICE_IOMMUFD_VFIO, &err)) {
> +        error_report_err(err);
> +        return false;
> +    }
> +    return true;
> +}
> +
>   static const VMStateDescription vfio_device_vmstate = {
>       .name = "vfio-iommufd-device",
>       .version_id = 0,
>       .minimum_version_id = 0,
> +    .post_load = vfio_device_post_load,
>       .needed = cpr_needed_for_reuse,
>       .fields = (VMStateField[]) {
> +        VMSTATE_INT32(devid, VFIODevice),
>           VMSTATE_END_OF_LIST()
>       }
>   };
> diff --git a/hw/vfio/iommufd.c b/hw/vfio/iommufd.c
> index c49a7e7..d980684 100644
> --- a/hw/vfio/iommufd.c
> +++ b/hw/vfio/iommufd.c
> @@ -32,9 +32,6 @@
>   #include "vfio-helpers.h"
>   #include "vfio-listener.h"
>   
> -#define TYPE_HOST_IOMMU_DEVICE_IOMMUFD_VFIO             \
> -            TYPE_HOST_IOMMU_DEVICE_IOMMUFD "-vfio"
> -
>   static int iommufd_cdev_map(const VFIOContainerBase *bcontainer, hwaddr iova,
>                               ram_addr_t size, void *vaddr, bool readonly)
>   {
> @@ -557,7 +554,8 @@ static bool iommufd_cdev_attach(const char *name, VFIODevice *vbasedev,
>   
>       space = vfio_address_space_get(as);
>   
> -    if (!vfio_device_hiod_create_and_realize(vbasedev,
> +    if (!vbasedev->cpr.reused &&
> +        !vfio_device_hiod_create_and_realize(vbasedev,
>               TYPE_HOST_IOMMU_DEVICE_IOMMUFD_VFIO, errp)) {
>           goto err_alloc_ioas;
>       }
> diff --git a/hw/vfio/vfio-iommufd.h b/hw/vfio/vfio-iommufd.h
> index cc57a05..148ce89 100644
> --- a/hw/vfio/vfio-iommufd.h
> +++ b/hw/vfio/vfio-iommufd.h
> @@ -11,6 +11,9 @@
>   
>   #include "hw/vfio/vfio-container-base.h"
>   
> +#define TYPE_HOST_IOMMU_DEVICE_IOMMUFD_VFIO             \
> +            TYPE_HOST_IOMMU_DEVICE_IOMMUFD "-vfio"
> +
>   typedef struct VFIODevice VFIODevice;
>   
>   typedef struct VFIOIOASHwpt {