On Thu, Apr 08, 2021 at 10:55:34PM +0300, Anton Kuchin wrote:
> Make virtio-fs take into account server capabilities.
> 
> Just returning requested features assumes they all of then are implemented
> by server and results in setting unsupported configuration if some of them
> are absent.
> 
> Signed-off-by: Anton Kuchin <antonkuchin@yandex-team.ru>
> ---
>  hw/virtio/vhost-user-fs.c | 17 +++++++++++++----
>  1 file changed, 13 insertions(+), 4 deletions(-)
> 
> diff --git a/hw/virtio/vhost-user-fs.c b/hw/virtio/vhost-user-fs.c
> index ac4fc34b36..6cf983ba0e 100644
> --- a/hw/virtio/vhost-user-fs.c
> +++ b/hw/virtio/vhost-user-fs.c
> @@ -24,6 +24,14 @@
>  #include "monitor/monitor.h"
>  #include "sysemu/sysemu.h"
>  
> +static const int user_feature_bits[] = {
> +    VIRTIO_F_VERSION_1,
> +    VIRTIO_RING_F_INDIRECT_DESC,
> +    VIRTIO_RING_F_EVENT_IDX,
> +    VIRTIO_F_NOTIFY_ON_EMPTY,
> +    VHOST_INVALID_FEATURE_BIT
> +};

Please add:

VIRTIO_F_RING_PACKED
VIRTIO_F_IOMMU_PLATFORM

QEMU's virtiofsd does not enable either of these for now, but it's worth
allowing the vhost-user device backend to participate in negotiation so
that this can change in the future (or alternative virtiofsd
implementations can support these features).