Re: [PATCH v3 1/1] s390: virtio: let arch accept devices without IOMMU feature

[Heiko Carstens <heiko.carstens@de.ibm.com>]

On Wed, Jun 17, 2020 at 12:43:57PM +0200, Pierre Morel wrote:
> An architecture protecting the guest memory against unauthorized host
> access may want to enforce VIRTIO I/O device protection through the
> use of VIRTIO_F_IOMMU_PLATFORM.
> 
> Let's give a chance to the architecture to accept or not devices
> without VIRTIO_F_IOMMU_PLATFORM.
> 
> Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
> Acked-by: Jason Wang <jasowang@redhat.com>
> Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
> ---
>  arch/s390/mm/init.c     |  6 ++++++
>  drivers/virtio/virtio.c | 22 ++++++++++++++++++++++
>  include/linux/virtio.h  |  2 ++
>  3 files changed, 30 insertions(+)
> 
> diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c
> index 6dc7c3b60ef6..215070c03226 100644
> --- a/arch/s390/mm/init.c
> +++ b/arch/s390/mm/init.c
> @@ -45,6 +45,7 @@
>  #include <asm/kasan.h>
>  #include <asm/dma-mapping.h>
>  #include <asm/uv.h>
> +#include <linux/virtio.h>
> 
>  pgd_t swapper_pg_dir[PTRS_PER_PGD] __section(.bss..swapper_pg_dir);
> 
> @@ -161,6 +162,11 @@ bool force_dma_unencrypted(struct device *dev)
>  	return is_prot_virt_guest();
>  }
> 
> +int arch_needs_virtio_iommu_platform(struct virtio_device *dev)
> +{
> +	return is_prot_virt_guest();
> +}
> +
>  /* protected virtualization */
>  static void pv_init(void)

Can we please stop dumping random code to arch/s390/mm/init.c?

All the protected virtualization functions should go into a separate
file (e.g. mem_encrypt.c like on x86), some of which could also be in
header files.

Please consider this a comment for the future.. just go ahead with
this patch as-is.