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

Pierre Morel
2020-06-16T07:35:31Z

On 2020-06-16 08:55, Christian Borntraeger wrote:
>
>
> On 15.06.20 14:39, 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@linux.ibm.com>
>
>
> Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>

Thanks,

>
> Shouldnt we maybe add a pr_warn if that happens to help the admins to understand what is going on?
>
>

Yes, Connie asked for it too, good that you remind it to me, I add it.

Thanks,
Pierre

>> ---
>> 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 */
>>

--
Pierre Morel
IBM Lab Boeblingen