Re: [PATCH v4 2/2] s390: virtio: PV needs VIRTIO I/O device protection

Christian Borntraeger
2020-07-07T11:13:59Z

On 07.07.20 10:44, Pierre Morel wrote:
> S390, protecting the guest memory against unauthorized host access
> needs to enforce VIRTIO I/O device protection through the use of
> VIRTIO_F_VERSION_1 and VIRTIO_F_IOMMU_PLATFORM.
>
> Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
> ---
> arch/s390/kernel/uv.c | 25 +++++++++++++++++++++++++
> 1 file changed, 25 insertions(+)
>
> diff --git a/arch/s390/kernel/uv.c b/arch/s390/kernel/uv.c
> index c296e5c8dbf9..106330f6eda1 100644
> --- a/arch/s390/kernel/uv.c
> +++ b/arch/s390/kernel/uv.c
> @@ -14,6 +14,7 @@
> #include <linux/memblock.h>
> #include <linux/pagemap.h>
> #include <linux/swap.h>
> +#include <linux/virtio_config.h>
> #include <asm/facility.h>
> #include <asm/sections.h>
> #include <asm/uv.h>
> @@ -413,3 +414,27 @@ static int __init uv_info_init(void)
> }
> device_initcall(uv_info_init);
> #endif
> +
> +/*
> + * arch_validate_virtio_iommu_platform
> + * @dev: the VIRTIO device being added
> + *
> + * Return value: returns -ENODEV if any features of the
> + * device breaks the protected virtualization
> + * 0 otherwise.
> + */
> +int arch_validate_virtio_features(struct virtio_device *dev)
> +{
> + if (!virtio_has_feature(dev, VIRTIO_F_VERSION_1)) {
> + dev_warn(&dev->dev, "device must provide VIRTIO_F_VERSION_1\n");

I think you only want to warn if is_prot_virt_guest is true? We certainly
want to be able to run as a guest of older hypervisors with virtio 0.95, no?

> + return is_prot_virt_guest() ? -ENODEV : 0;
> + }
> +
> + if (!virtio_has_feature(dev, VIRTIO_F_IOMMU_PLATFORM)) {
> + dev_warn(&dev->dev,
> + "device must provide VIRTIO_F_IOMMU_PLATFORM\n");

same here.
> + return is_prot_virt_guest() ? -ENODEV : 0;
> + }
> +
> + return 0;
> +}
>