Linux Virtualization - Jun 2020 - [PATCH v2 1/1] s390: virtio: let arch accept devices without IOMMU feature

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 at linux.ibm.com>

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

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

> ---
>  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 */
>

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

On Tue, 16 Jun 2020 09:35:19 +0200
Pierre Morel <pmorel at linux.ibm.com> wrote:
> 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 at linux.ibm.com>  
> > 
> > 
> > Acked-by: Christian Borntraeger <borntraeger at 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.
Yes, please :)