Re: [PATCH v2 2/2] vfio/container: Fix vfio_container_post_load()

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

On 6/27/2025 2:33 AM, Zhenzhong Duan wrote:
> When there are multiple VFIO containers, vioc->dma_map is restored
> multiple times, this made only first container work and remaining
> containers using vioc->dma_map restored by first container.
> 
> Fix it by save and restore vioc->dma_map locally. saved_dma_map in
> VFIOContainerCPR becomes useless and is removed.
> 
> Fixes: 7e9f21411302 ("vfio/container: restore DMA vaddr")
> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
> ---
>   include/hw/vfio/vfio-cpr.h |  7 ++++---
>   hw/vfio/cpr-legacy.c       | 23 +++++++++--------------
>   2 files changed, 13 insertions(+), 17 deletions(-)
> 
> diff --git a/include/hw/vfio/vfio-cpr.h b/include/hw/vfio/vfio-cpr.h
> index 8bf85b9f4e..dbb2a16b7a 100644
> --- a/include/hw/vfio/vfio-cpr.h
> +++ b/include/hw/vfio/vfio-cpr.h
> @@ -16,14 +16,15 @@ struct VFIOContainer;
>   struct VFIOContainerBase;
>   struct VFIOGroup;
>   
> +typedef int (*dma_map_fn)(const struct VFIOContainerBase *bcontainer,
> +                          hwaddr iova, ram_addr_t size, void *vaddr,
> +                          bool readonly, MemoryRegion *mr);
> +
>   typedef struct VFIOContainerCPR {
>       Error *blocker;
>       bool vaddr_unmapped;
>       NotifierWithReturn transfer_notifier;
>       MemoryListener remap_listener;
> -    int (*saved_dma_map)(const struct VFIOContainerBase *bcontainer,
> -                         hwaddr iova, ram_addr_t size,
> -                         void *vaddr, bool readonly, MemoryRegion *mr);
>   } VFIOContainerCPR;
>   
>   typedef struct VFIODeviceCPR {
> diff --git a/hw/vfio/cpr-legacy.c b/hw/vfio/cpr-legacy.c
> index 0a5d1bd480..1216717546 100644
> --- a/hw/vfio/cpr-legacy.c
> +++ b/hw/vfio/cpr-legacy.c
> @@ -99,20 +99,21 @@ static int vfio_container_post_load(void *opaque, int version_id)
>   {
>       VFIOContainer *container = opaque;
>       VFIOContainerBase *bcontainer = &container->bcontainer;
> -    VFIOGroup *group;
> +    VFIOIOMMUClass *vioc = VFIO_IOMMU_GET_CLASS(bcontainer);
> +    dma_map_fn saved_dma_map = vioc->dma_map;
>       Error *local_err = NULL;
>   
> +    /* During incoming CPR, divert calls to dma_map. */
> +    vioc->dma_map = vfio_legacy_cpr_dma_map;
> +
>       if (!vfio_listener_register(bcontainer, &local_err)) {
>           error_report_err(local_err);
>           return -1;
>       }
>   
> -    QLIST_FOREACH(group, &container->group_list, container_next) {
> -        VFIOIOMMUClass *vioc = VFIO_IOMMU_GET_CLASS(bcontainer);
> +    /* Restore original dma_map function */
> +    vioc->dma_map = saved_dma_map;
>   
> -        /* Restore original dma_map function */
> -        vioc->dma_map = container->cpr.saved_dma_map;
> -    }
>       return 0;
>   }
>   
> @@ -148,6 +149,7 @@ static int vfio_cpr_fail_notifier(NotifierWithReturn *notifier,
>            */
>   
>           VFIOIOMMUClass *vioc = VFIO_IOMMU_GET_CLASS(bcontainer);
> +        dma_map_fn saved_dma_map = vioc->dma_map;
>           vioc->dma_map = vfio_legacy_cpr_dma_map;
>   
>           container->cpr.remap_listener = (MemoryListener) {
> @@ -158,7 +160,7 @@ static int vfio_cpr_fail_notifier(NotifierWithReturn *notifier,
>                                    bcontainer->space->as);
>           memory_listener_unregister(&container->cpr.remap_listener);
>           container->cpr.vaddr_unmapped = false;
> -        vioc->dma_map = container->cpr.saved_dma_map;
> +        vioc->dma_map = saved_dma_map;
>       }
>       return 0;
>   }
> @@ -179,13 +181,6 @@ bool vfio_legacy_cpr_register_container(VFIOContainer *container, Error **errp)
>   
>       vmstate_register(NULL, -1, &vfio_container_vmstate, container);
>   
> -    /* During incoming CPR, divert calls to dma_map. */
> -    VFIOIOMMUClass *vioc = VFIO_IOMMU_GET_CLASS(bcontainer);
> -    container->cpr.saved_dma_map = vioc->dma_map;
> -    if (cpr_is_incoming()) {
> -        vioc->dma_map = vfio_legacy_cpr_dma_map;
> -    }
> -
>       migration_add_notifier_mode(&container->cpr.transfer_notifier,
>                                   vfio_cpr_fail_notifier,
>                                   MIG_MODE_CPR_TRANSFER);

Reviewed-by: Steve Sistare <steven.sistare@oracle.com>