linux-kernel - Re: [PATCH v6 2/2] s390: virtio: PV needs VIRTIO I/O device protection

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Date:   Tue, 14 Jul 2020 13:42:46 +0200
From:   Christian Borntraeger <borntraeger@...ibm.com>
To:     Pierre Morel <pmorel@...ux.ibm.com>, linux-kernel@...r.kernel.org
Cc:     pasic@...ux.ibm.com, frankja@...ux.ibm.com, mst@...hat.com,
        jasowang@...hat.com, cohuck@...hat.com, kvm@...r.kernel.org,
        linux-s390@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, thomas.lendacky@....com,
        david@...son.dropbear.id.au, linuxram@...ibm.com,
        hca@...ux.ibm.com, gor@...ux.ibm.com
Subject: Re: [PATCH v6 2/2] s390: virtio: PV needs VIRTIO I/O device
 protection


On 14.07.20 13:38, Pierre Morel wrote:
> If protected virtualization is active on s390, the virtio queues are
> not accessible to the host, unless VIRTIO_F_IOMMU_PLATFORM has been
> negotiated. Use the new arch_validate_virtio_features() interface to
> fail probe if that's not the case, preventing a host error on access
> attempt.
> 
> Signed-off-by: Pierre Morel <pmorel@...ux.ibm.com>
> Reviewed-by: Cornelia Huck <cohuck@...hat.com>
> Acked-by: Halil Pasic <pasic@...ux.ibm.com>

We will probably move this (and other related code) into a new file,
but we can do that later. 
As for now:

Acked-by: Christian Borntraeger <borntraeger@...ibm.com>

> ---
>  arch/s390/mm/init.c | 28 ++++++++++++++++++++++++++++
>  1 file changed, 28 insertions(+)
> 
> diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c
> index 6dc7c3b60ef6..26efb663bac2 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_config.h>
>  
>  pgd_t swapper_pg_dir[PTRS_PER_PGD] __section(.bss..swapper_pg_dir);
>  
> @@ -161,6 +162,33 @@ bool force_dma_unencrypted(struct device *dev)
>  	return is_prot_virt_guest();
>  }
>  
> +/*
> + * arch_validate_virtio_features
> + * @dev: the VIRTIO device being added
> + *
> + * Return an error if required features are missing on a guest running
> + * with protected virtualization.
> + */
> +int arch_validate_virtio_features(struct virtio_device *dev)
> +{
> +	if (!is_prot_virt_guest())
> +		return 0;
> +
> +	if (!virtio_has_feature(dev, VIRTIO_F_VERSION_1)) {
> +		dev_warn(&dev->dev,
> +			 "legacy virtio not supported with protected virtualizatio\n");
> +		return -ENODEV;
> +	}
> +
> +	if (!virtio_has_feature(dev, VIRTIO_F_IOMMU_PLATFORM)) {
> +		dev_warn(&dev->dev,
> +			 "support for limited memory access required for protected virtualization\n");
> +		return -ENODEV;
> +	}
> +
> +	return 0;
> +}
> +
>  /* protected virtualization */
>  static void pv_init(void)
>  {
>