Re: [PATCH v2 1/1] s390: virtio: let arch accept devices without IOMMU feature

[Jason Wang]

On 2020/6/15 äå8:39, 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@xxxxxxxxxxxxx>


Acked-by: Jason Wang <jasowang@xxxxxxxxxx>


> ---
>   arch/s390/mm/init.c     | 6 ++++++
>   drivers/virtio/virtio.c | 9 +++++++++
>   include/linux/virtio.h  | 2 ++
>   3 files changed, 17 insertions(+)
>
> diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c
> index 87b2d024e75a..3f04ad09650f 100644
> --- a/arch/s390/mm/init.c
> +++ b/arch/s390/mm/init.c
> @@ -46,6 +46,7 @@
>   #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);
>   
> @@ -162,6 +163,11 @@ bool force_dma_unencrypted(struct device *dev)
>   	return is_prot_virt_guest();
>   }
>   
> +int arch_needs_iommu_platform(struct virtio_device *dev)
> +{
> +	return is_prot_virt_guest();
> +}
> +
>   /* protected virtualization */
>   static void pv_init(void)
>   {
> diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
> index a977e32a88f2..30091089bee8 100644
> --- a/drivers/virtio/virtio.c
> +++ b/drivers/virtio/virtio.c
> @@ -167,6 +167,11 @@ void virtio_add_status(struct virtio_device *dev, unsigned int status)
>   }
>   EXPORT_SYMBOL_GPL(virtio_add_status);
>   
> +int __weak arch_needs_iommu_platform(struct virtio_device *dev)
> +{
> +	return 0;
> +}
> +
>   int virtio_finalize_features(struct virtio_device *dev)
>   {
>   	int ret = dev->config->finalize_features(dev);
> @@ -179,6 +184,10 @@ int virtio_finalize_features(struct virtio_device *dev)
>   	if (!virtio_has_feature(dev, VIRTIO_F_VERSION_1))
>   		return 0;
>   
> +	if (arch_needs_iommu_platform(dev) &&
> +		!virtio_has_feature(dev, VIRTIO_F_IOMMU_PLATFORM))
> +		return -EIO;
> +
>   	virtio_add_status(dev, VIRTIO_CONFIG_S_FEATURES_OK);
>   	status = dev->config->get_status(dev);
>   	if (!(status & VIRTIO_CONFIG_S_FEATURES_OK)) {
> diff --git a/include/linux/virtio.h b/include/linux/virtio.h
> index a493eac08393..2c46b310c38c 100644
> --- a/include/linux/virtio.h
> +++ b/include/linux/virtio.h
> @@ -195,4 +195,6 @@ void unregister_virtio_driver(struct virtio_driver *drv);
>   #define module_virtio_driver(__virtio_driver) \
>   	module_driver(__virtio_driver, register_virtio_driver, \
>   			unregister_virtio_driver)
> +
> +int arch_needs_iommu_platform(struct virtio_device *dev);
>   #endif /* _LINUX_VIRTIO_H */