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Date: Fri, 26 Jan 2018 09:46:45 -0700
From: Alex Williamson <alex.williamson@redhat.com>
Message-ID: <20180126094645.7443c4e0@w520.home>
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Subject: Re: [Qemu-devel] [PATCH v2 3/4] vfio: listener unregister before
 unset container
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To: Peter Xu <peterx@redhat.com>
Cc: qemu-devel@nongnu.org, David Gibson <david@gibson.dropbear.id.au>, Paolo Bonzini <pbonzini@redhat.com>, Peter Maydell <peter.maydell@linaro.org>, "Michael S . Tsirkin" <mst@redhat.com>, Alexey Kardashevskiy <aik@ozlabs.ru>

On Mon, 22 Jan 2018 14:02:43 +0800
Peter Xu <peterx@redhat.com> wrote:

> After next patch, listener unregister will need the container to be
> alive.  Let's move this unregister phase to be before unset container,
> since that operation will free the backend container in kernel,
> otherwise we'll get these after next patch:
> 
> qemu-system-x86_64: VFIO_UNMAP_DMA: -22
> qemu-system-x86_64: vfio_dma_unmap(0x559bf53a4590, 0x0, 0xa0000) = -22 (Invalid argument)
> 
> Signed-off-by: Peter Xu <peterx@redhat.com>
> ---

Acked-by: Alex Williamson <alex.williamson@redhat.com>

Not sure which branch this will go through, let me know if mine.
Thanks,

Alex

>  hw/vfio/common.c | 16 ++++++++++++----
>  1 file changed, 12 insertions(+), 4 deletions(-)
> 
> diff --git a/hw/vfio/common.c b/hw/vfio/common.c
> index b77be3a8b3..76cf28d462 100644
> --- a/hw/vfio/common.c
> +++ b/hw/vfio/common.c
> @@ -1161,19 +1161,27 @@ static void vfio_disconnect_container(VFIOGroup *group)
>  {
>      VFIOContainer *container = group->container;
>  
> +    QLIST_REMOVE(group, container_next);
> +    group->container = NULL;
> +
> +    /*
> +     * Explicitly release the listener first before unset container,
> +     * since unset may destroy the backend container if it's the last
> +     * group.
> +     */
> +    if (QLIST_EMPTY(&container->group_list)) {
> +        vfio_listener_release(container);
> +    }
> +
>      if (ioctl(group->fd, VFIO_GROUP_UNSET_CONTAINER, &container->fd)) {
>          error_report("vfio: error disconnecting group %d from container",
>                       group->groupid);
>      }
>  
> -    QLIST_REMOVE(group, container_next);
> -    group->container = NULL;
> -
>      if (QLIST_EMPTY(&container->group_list)) {
>          VFIOAddressSpace *space = container->space;
>          VFIOGuestIOMMU *giommu, *tmp;
>  
> -        vfio_listener_release(container);
>          QLIST_REMOVE(container, next);
>  
>          QLIST_FOREACH_SAFE(giommu, &container->giommu_list, giommu_next, tmp) {