Re: [PATCH V1 07/26] vfio/container: recover from unmap-all-vaddr failure

["Cédric Le Goater" <clg@redhat.com>]

On 1/29/25 15:43, Steve Sistare wrote:
> If there are multiple containers and unmap-all fails for some container, we
> need to remap vaddr for the other containers for which unmap-all succeeded.
> Recover by walking all address ranges of all containers to restore the vaddr
> for each.  Do so by invoking the vfio listener callback, and passing a new
> "remap" flag that tells it to restore a mapping without re-allocating new
> userland data structures.
> 
> Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
> ---
>   hw/vfio/common.c              | 47 ++++++++++++++++++++++++++++++++++++++++++-
>   hw/vfio/cpr-legacy.c          | 44 ++++++++++++++++++++++++++++++++++++++++
>   include/hw/vfio/vfio-common.h |  6 +++++-
>   3 files changed, 95 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/vfio/common.c b/hw/vfio/common.c
> index 7370332..c8ee71a 100644
> --- a/hw/vfio/common.c
> +++ b/hw/vfio/common.c
> @@ -580,6 +580,13 @@ static void vfio_listener_region_add(MemoryListener *listener,
>   {
>       VFIOContainerBase *bcontainer = container_of(listener, VFIOContainerBase,
>                                                    listener);
> +    vfio_container_region_add(bcontainer, section, false);
> +}
> +
> +void vfio_container_region_add(VFIOContainerBase *bcontainer,
> +                               MemoryRegionSection *section,
> +                               bool remap)
> +{

vfio_container_region_add() is already complex enough. Please consider
doing an initial refactoring before adding a new code path. It would be
welcome !

>       hwaddr iova, end;
>       Int128 llend, llsize;
>       void *vaddr;
> @@ -614,6 +621,30 @@ static void vfio_listener_region_add(MemoryListener *listener,
>           int iommu_idx;
>   
>           trace_vfio_listener_region_add_iommu(section->mr->name, iova, end);
> +
> +        /*
> +         * If remap, then VFIO_DMA_UNMAP_FLAG_VADDR has been called, and we
> +         * want to remap the vaddr.  vfio_container_region_add was already
> +         * called in the past, so the giommu already exists.  Find it and
> +         * replay it, which calls vfio_dma_map further down the stack.
> +         */
> +
> +        if (remap) {
> +            hwaddr as_offset = section->offset_within_address_space;
> +            hwaddr iommu_offset = as_offset - section->offset_within_region;
> +
> +            QLIST_FOREACH(giommu, &bcontainer->giommu_list, giommu_next) {
> +                if (giommu->iommu_mr == iommu_mr &&
> +                    giommu->iommu_offset == iommu_offset) {
> +                    memory_region_iommu_replay(giommu->iommu_mr, &giommu->n);
> +                    return;
> +                }
> +            }
> +            error_report("Container cannot find iommu region %s offset %lx",
> +                memory_region_name(section->mr), iommu_offset);

error_report() are not welcomed. We need to find a way to propagate
this error.

> +            goto fail;
> +        }

Please introduce a vfio_cpr helper for the section above and move it
under the hw/vfio/cpr* files.


>           /*
>            * FIXME: For VFIO iommu types which have KVM acceleration to
>            * avoid bouncing all map/unmaps through qemu this way, this
> @@ -656,7 +687,21 @@ static void vfio_listener_region_add(MemoryListener *listener,
>        * about changes.
>        */
>       if (memory_region_has_ram_discard_manager(section->mr)) {
> -        vfio_register_ram_discard_listener(bcontainer, section);
> +        /*
> +         * If remap, then VFIO_DMA_UNMAP_FLAG_VADDR has been called, and we
> +         * want to remap the vaddr.  vfio_container_region_add was already
> +         * called in the past, so the ram discard listener already exists.
> +         * Call its populate function directly, which calls vfio_dma_map.
> +         */
> +        if (remap)  {
> +            VFIORamDiscardListener *vrdl =
> +                vfio_find_ram_discard_listener(bcontainer, section);
> +            if (vrdl->listener.notify_populate(&vrdl->listener, section)) {
> +                error_report("listener.notify_populate failed");
> +            }
> +        } else {
> +            vfio_register_ram_discard_listener(bcontainer, section);
> +        }

idem.

>           return;
>       }
>   
> diff --git a/hw/vfio/cpr-legacy.c b/hw/vfio/cpr-legacy.c
> index f3a31d1..3139de1 100644
> --- a/hw/vfio/cpr-legacy.c
> +++ b/hw/vfio/cpr-legacy.c
> @@ -26,9 +26,18 @@ static bool vfio_dma_unmap_vaddr_all(VFIOContainer *container, Error **errp)
>           error_setg_errno(errp, errno, "vfio_dma_unmap_vaddr_all");
>           return false;
>       }
> +    container->vaddr_unmapped = true;
>       return true;>   }
>   
> +static void vfio_region_remap(MemoryListener *listener,
> +                              MemoryRegionSection *section)
> +{
> +    VFIOContainer *container = container_of(listener, VFIOContainer,
> +                                            remap_listener);
> +    vfio_container_region_add(&container->bcontainer, section, true);
> +}
> +
>   static bool vfio_cpr_supported(VFIOContainer *container, Error **errp)
>   {
>       if (!ioctl(container->fd, VFIO_CHECK_EXTENSION, VFIO_UPDATE_VADDR)) {
> @@ -88,6 +97,37 @@ static const VMStateDescription vfio_container_vmstate = {
>       }
>   };
>   
> +static int vfio_cpr_fail_notifier(NotifierWithReturn *notifier,
> +                                  MigrationEvent *e, Error **errp)
> +{
> +    VFIOContainer *container =
> +        container_of(notifier, VFIOContainer, cpr_transfer_notifier);
> +    VFIOContainerBase *bcontainer = &container->bcontainer;
> +
> +    if (e->type != MIG_EVENT_PRECOPY_FAILED) {
> +        return 0;
> +    }
> +
> +    if (container->vaddr_unmapped) {
> +        /*
> +         * Force a call to vfio_region_remap for each mapped section by
> +         * temporarily registering a listener, which calls vfio_dma_map
> +         * further down the stack. Set reused so vfio_dma_map restores vaddr.
> +         */
> +        container->reused = true;
> +        container->remap_listener = (MemoryListener) {
> +            .name = "vfio recover",
> +            .region_add = vfio_region_remap
> +        };
> +        memory_listener_register(&container->remap_listener,
> +                                 bcontainer->space->as);
> +        memory_listener_unregister(&container->remap_listener);
> +        container->reused = false;
> +        container->vaddr_unmapped = false;
> +    }> +    return 0;
> +}
> +
>   bool vfio_legacy_cpr_register_container(VFIOContainer *container, Error **errp)
>   {
>       VFIOContainerBase *bcontainer = &container->bcontainer;
> @@ -104,6 +144,9 @@ bool vfio_legacy_cpr_register_container(VFIOContainer *container, Error **errp)
>   
>       vmstate_register(NULL, -1, &vfio_container_vmstate, container);
>   
> +    migration_add_notifier_mode(&container->cpr_transfer_notifier,
> +                                vfio_cpr_fail_notifier,
> +                                MIG_MODE_CPR_TRANSFER);
>       return true;>   }
>   
> @@ -114,4 +157,5 @@ void vfio_legacy_cpr_unregister_container(VFIOContainer *container)
>       vfio_cpr_unregister_container(bcontainer);
>       migrate_del_blocker(&container->cpr_blocker);
>       vmstate_unregister(NULL, &vfio_container_vmstate, container);
> +    migration_remove_notifier(&container->cpr_transfer_notifier);
>   }
> diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h
> index 1e974e0..8a4a658 100644
> --- a/include/hw/vfio/vfio-common.h
> +++ b/include/hw/vfio/vfio-common.h
> @@ -86,6 +86,9 @@ typedef struct VFIOContainer {
>       unsigned iommu_type;
>       Error *cpr_blocker;
>       bool reused;
> +    bool vaddr_unmapped;
> +    NotifierWithReturn cpr_transfer_notifier;
> +    MemoryListener remap_listener;

There are 5 attributes related to CPR, please add a CPR struct to hold
them all.



Thanks,

C.


>       QLIST_HEAD(, VFIOGroup) group_list;
>   } VFIOContainer;
>   
> @@ -311,7 +314,8 @@ int vfio_devices_query_dirty_bitmap(const VFIOContainerBase *bcontainer,
>   int vfio_get_dirty_bitmap(const VFIOContainerBase *bcontainer, uint64_t iova,
>                             uint64_t size, ram_addr_t ram_addr, Error **errp);
>   
> -void vfio_listener_register(VFIOContainerBase *bcontainer);
> +void vfio_container_region_add(VFIOContainerBase *bcontainer,
> +                               MemoryRegionSection *section, bool remap);
>   
>   /* Returns 0 on success, or a negative errno. */
>   bool vfio_device_get_name(VFIODevice *vbasedev, Error **errp);