Re: [PATCH v7 00/19] virtio: alignment issues

[Jason Wang <jasowang@redhat.com>]

----- Original Message -----
> 
> This is an alternative to
> 	vhost: force spec specified alignment on types
> which is a bit safer as it does not change UAPI.
> I still think it's best to change the UAPI header as well,
> we can do that as a follow-up cleanup.
> 
> changes from v6:
> 	add missing header includes all over the place
> changes from v5:
> 	ack for mellanox patch
> 	fixup to remoteproc
> changes from v4:
> 	fixup to issues reported by kbuild
> changes from v3:
> 	tools/virtio fixes
> 	a bunch more cleanups that now become possible
> 
> Changes from v2:
> 	don't change struct name, instead add ifndef
> 	so kernel does not see the legacy UAPI version.
> 
> Jason, can you pls ack one of the approaches?

I prefer this approach but it looks a little bit risky for 5.7. Can we
do this in 5.8?

Instead of using Kconfig, could we simply fail the initalization of
vhost like:

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 0395229486a9..e9f6a008ed12 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -2636,6 +2636,11 @@ EXPORT_SYMBOL_GPL(vhost_dequeue_msg);
 
 static int __init vhost_init(void)
 {
+	struct vhost_virtqueue *vq;
+
+	if (__alignof__ *vq->avail > VRING_AVAIL_ALIGN_SIZE)
+		return -ENOTSUPP;
+
 	return 0;
 }

Thanks

> 
> 
> Matej Genci (1):
>   virtio: add VIRTIO_RING_NO_LEGACY
> 
> Michael S. Tsirkin (18):
>   tools/virtio: define aligned attribute
>   tools/virtio: make asm/barrier.h self contained
>   tools/virtio: define __KERNEL__
>   virtgpu: pull in uaccess.h
>   virtio-rng: pull in slab.h
>   remoteproc: pull in slab.h
>   virtio_input: pull in slab.h
>   virtio: stop using legacy struct vring in kernel
>   vhost: force spec specified alignment on types
>   virtio: add legacy init/size APIs
>   virtio_ring: switch to virtio_legacy_init/size
>   tools/virtio: switch to virtio_legacy_init/size
>   vop: switch to virtio_legacy_init/size
>   remoteproc: switch to virtio_legacy_init/size
>   mellanox: switch to virtio_legacy_init/size
>   vhost: option to fetch descriptors through an independent struct
>   vhost: use batched version by default
>   vhost: batching fetches
> 
>  drivers/block/virtio_blk.c               |   1 +
>  drivers/char/hw_random/virtio-rng.c      |   1 +
>  drivers/gpu/drm/virtio/virtgpu_ioctl.c   |   1 +
>  drivers/misc/mic/vop/vop_main.c          |   5 +-
>  drivers/misc/mic/vop/vop_vringh.c        |   8 +-
>  drivers/platform/mellanox/mlxbf-tmfifo.c |   6 +-
>  drivers/remoteproc/remoteproc_core.c     |   2 +-
>  drivers/remoteproc/remoteproc_sysfs.c    |   1 +
>  drivers/remoteproc/remoteproc_virtio.c   |   2 +-
>  drivers/vhost/test.c                     |   2 +-
>  drivers/vhost/vhost.c                    | 271 +++++++++++++++--------
>  drivers/vhost/vhost.h                    |  23 +-
>  drivers/virtio/virtio_input.c            |   1 +
>  drivers/virtio/virtio_pci_modern.c       |   1 +
>  drivers/virtio/virtio_ring.c             |  15 +-
>  include/linux/virtio.h                   |   1 -
>  include/linux/virtio_ring.h              |  46 ++++
>  include/linux/vringh.h                   |   1 +
>  include/uapi/linux/virtio_ring.h         |  30 ++-
>  tools/virtio/Makefile                    |   2 +-
>  tools/virtio/asm/barrier.h               |   1 +
>  tools/virtio/linux/compiler.h            |   1 +
>  tools/virtio/ringtest/virtio_ring_0_9.c  |   6 +-
>  tools/virtio/virtio_test.c               |   6 +-
>  tools/virtio/vringh_test.c               |  18 +-
>  25 files changed, 311 insertions(+), 141 deletions(-)
> 
> --
> MST
> 
> 

>