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SubjectRe: [PATCH v5 2/2] s390: virtio: PV needs VIRTIO I/O device protection
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On 2020-07-09 10:57, Cornelia Huck wrote:
> On Thu, 9 Jul 2020 10:39:19 +0200
> Pierre Morel <pmorel@linux.ibm.com> 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@linux.ibm.com>
>> ---
>> arch/s390/mm/init.c | 27 +++++++++++++++++++++++++++
>> 1 file changed, 27 insertions(+)
>>
>> diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c
>> index 6dc7c3b60ef6..b8e6f90117da 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 +162,32 @@ 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, "device must provide VIRTIO_F_VERSION_1\n");
>
> I'd probably use "legacy virtio not supported with protected
> virtualization".
>
>> + return -ENODEV;
>> + }
>> +
>> + if (!virtio_has_feature(dev, VIRTIO_F_IOMMU_PLATFORM)) {
>> + dev_warn(&dev->dev,
>> + "device must provide VIRTIO_F_IOMMU_PLATFORM\n");
>
> "support for limited memory access required for protected
> virtualization"
>
> ?
>
> Mentioning the feature flag is shorter in both cases, though.

And I think easier to look for in case of debugging purpose.
I change it if there is more demands.

>
>> + return -ENODEV;
>> + }
>> +
>> + return 0;
>> +}
>> +
>> /* protected virtualization */
>> static void pv_init(void)
>> {
>
> Either way,
>
> Reviewed-by: Cornelia Huck <cohuck@redhat.com>
>

Thanks,
Pierre


--
Pierre Morel
IBM Lab Boeblingen

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