Linux Virtualization - Jun 2020 - [PATCH v3 1/1] s390: virtio: let arch accept devices without IOMMU feature

On Wed, Jun 17, 2020 at 12:43:57PM +0200, 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: Jason Wang <jasowang at redhat.com>
> Acked-by: Christian Borntraeger <borntraeger at de.ibm.com>
> ---
>  arch/s390/mm/init.c     |  6 ++++++
>  drivers/virtio/virtio.c | 22 ++++++++++++++++++++++
>  include/linux/virtio.h  |  2 ++
>  3 files changed, 30 insertions(+)
> 
> diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c
> index 6dc7c3b60ef6..215070c03226 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.h>
>  
>  pgd_t swapper_pg_dir[PTRS_PER_PGD] __section(.bss..swapper_pg_dir);
>  
> @@ -161,6 +162,11 @@ bool force_dma_unencrypted(struct device *dev)
>  	return is_prot_virt_guest();
>  }
>  
> +int arch_needs_virtio_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..aa8e01104f86 100644
> --- a/drivers/virtio/virtio.c
> +++ b/drivers/virtio/virtio.c
> @@ -167,6 +167,21 @@ void virtio_add_status(struct virtio_device *dev,
unsigned int status)
>  }
>  EXPORT_SYMBOL_GPL(virtio_add_status);
>  
> +/*
> + * arch_needs_virtio_iommu_platform - provide arch specific hook when
finalizing
> + *				      features for VIRTIO device dev
> + * @dev: the VIRTIO device being added
> + *
> + * Permits the platform to provide architecture specific functionality
when
> + * devices features are finalized. This is the default implementation.
> + * Architecture implementations can override this.
> + */
> +
> +int __weak arch_needs_virtio_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 +194,13 @@ int virtio_finalize_features(struct virtio_device
*dev)
>  	if (!virtio_has_feature(dev, VIRTIO_F_VERSION_1))
>  		return 0;
>  
> +	if (arch_needs_virtio_iommu_platform(dev) &&
> +		!virtio_has_feature(dev, VIRTIO_F_IOMMU_PLATFORM)) {
> +		dev_warn(&dev->dev,
> +			 "virtio: device must provide VIRTIO_F_IOMMU_PLATFORM\n");
> +		return -ENODEV;
> +	}
> +
>  	virtio_add_status(dev, VIRTIO_CONFIG_S_FEATURES_OK);
>  	status = dev->config->get_status(dev);
>  	if (!(status & VIRTIO_CONFIG_S_FEATURES_OK)) {
Well don't you need to check it *before* VIRTIO_F_VERSION_1, not after?


> diff --git a/include/linux/virtio.h b/include/linux/virtio.h
> index a493eac08393..e8526ae3463e 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_virtio_iommu_platform(struct virtio_device *dev);
>  #endif /* _LINUX_VIRTIO_H */
> -- 
> 2.25.1

On Mon, 29 Jun 2020 11:57:14 -0400
"Michael S. Tsirkin" <mst at redhat.com> wrote:
> On Wed, Jun 17, 2020 at 12:43:57PM +0200, 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: Jason Wang <jasowang at redhat.com>
> > Acked-by: Christian Borntraeger <borntraeger at de.ibm.com>
> > ---
> >  arch/s390/mm/init.c     |  6 ++++++
> >  drivers/virtio/virtio.c | 22 ++++++++++++++++++++++
> >  include/linux/virtio.h  |  2 ++
> >  3 files changed, 30 insertions(+)
> > @@ -179,6 +194,13 @@ int virtio_finalize_features(struct virtio_device
*dev)
> >  	if (!virtio_has_feature(dev, VIRTIO_F_VERSION_1))
> >  		return 0;
> >  
> > +	if (arch_needs_virtio_iommu_platform(dev) &&
> > +		!virtio_has_feature(dev, VIRTIO_F_IOMMU_PLATFORM)) {
> > +		dev_warn(&dev->dev,
> > +			 "virtio: device must provide
VIRTIO_F_IOMMU_PLATFORM\n");
> > +		return -ENODEV;
> > +	}
> > +
> >  	virtio_add_status(dev, VIRTIO_CONFIG_S_FEATURES_OK);
> >  	status = dev->config->get_status(dev);
> >  	if (!(status & VIRTIO_CONFIG_S_FEATURES_OK)) {  
> 
> Well don't you need to check it *before* VIRTIO_F_VERSION_1, not after?
But it's only available with VERSION_1 anyway, isn't it? So it probably
also needs to fail when this feature is needed if VERSION_1 has not been
negotiated, I think.

On 2020-06-29 17:57, Michael S. Tsirkin wrote:
> On Wed, Jun 17, 2020 at 12:43:57PM +0200, 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: Jason Wang <jasowang at redhat.com>
>> Acked-by: Christian Borntraeger <borntraeger at de.ibm.com>
>> ---
>>   arch/s390/mm/init.c     |  6 ++++++
>>   drivers/virtio/virtio.c | 22 ++++++++++++++++++++++
>>   include/linux/virtio.h  |  2 ++
>>   3 files changed, 30 insertions(+)
>>
>> diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c
>> index 6dc7c3b60ef6..215070c03226 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.h>
>>   
>>   pgd_t swapper_pg_dir[PTRS_PER_PGD] __section(.bss..swapper_pg_dir);
>>   
>> @@ -161,6 +162,11 @@ bool force_dma_unencrypted(struct device *dev)
>>   	return is_prot_virt_guest();
>>   }
>>   
>> +int arch_needs_virtio_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..aa8e01104f86 100644
>> --- a/drivers/virtio/virtio.c
>> +++ b/drivers/virtio/virtio.c
>> @@ -167,6 +167,21 @@ void virtio_add_status(struct virtio_device *dev,
unsigned int status)
>>   }
>>   EXPORT_SYMBOL_GPL(virtio_add_status);
>>   
>> +/*
>> + * arch_needs_virtio_iommu_platform - provide arch specific hook when
finalizing
>> + *				      features for VIRTIO device dev
>> + * @dev: the VIRTIO device being added
>> + *
>> + * Permits the platform to provide architecture specific functionality
when
>> + * devices features are finalized. This is the default implementation.
>> + * Architecture implementations can override this.
>> + */
>> +
>> +int __weak arch_needs_virtio_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 +194,13 @@ int virtio_finalize_features(struct virtio_device
*dev)
>>   	if (!virtio_has_feature(dev, VIRTIO_F_VERSION_1))
>>   		return 0;
>>   
>> +	if (arch_needs_virtio_iommu_platform(dev) &&
>> +		!virtio_has_feature(dev, VIRTIO_F_IOMMU_PLATFORM)) {
>> +		dev_warn(&dev->dev,
>> +			 "virtio: device must provide
VIRTIO_F_IOMMU_PLATFORM\n");
>> +		return -ENODEV;
>> +	}
>> +
>>   	virtio_add_status(dev, VIRTIO_CONFIG_S_FEATURES_OK);
>>   	status = dev->config->get_status(dev);
>>   	if (!(status & VIRTIO_CONFIG_S_FEATURES_OK)) {
> 
> Well don't you need to check it *before* VIRTIO_F_VERSION_1, not after?
Yes, you are right,

Thanks,

Pierre

-- 
Pierre Morel
IBM Lab Boeblingen

On 2020-06-29 18:05, Cornelia Huck wrote:
> On Mon, 29 Jun 2020 11:57:14 -0400
> "Michael S. Tsirkin" <mst at redhat.com> wrote:
> 
>> On Wed, Jun 17, 2020 at 12:43:57PM +0200, 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: Jason Wang <jasowang at redhat.com>
>>> Acked-by: Christian Borntraeger <borntraeger at de.ibm.com>
>>> ---
>>>   arch/s390/mm/init.c     |  6 ++++++
>>>   drivers/virtio/virtio.c | 22 ++++++++++++++++++++++
>>>   include/linux/virtio.h  |  2 ++
>>>   3 files changed, 30 insertions(+)
> 
>>> @@ -179,6 +194,13 @@ int virtio_finalize_features(struct
virtio_device *dev)
>>>   	if (!virtio_has_feature(dev, VIRTIO_F_VERSION_1))
>>>   		return 0;
>>>   
>>> +	if (arch_needs_virtio_iommu_platform(dev) &&
>>> +		!virtio_has_feature(dev, VIRTIO_F_IOMMU_PLATFORM)) {
>>> +		dev_warn(&dev->dev,
>>> +			 "virtio: device must provide
VIRTIO_F_IOMMU_PLATFORM\n");
>>> +		return -ENODEV;
>>> +	}
>>> +
>>>   	virtio_add_status(dev, VIRTIO_CONFIG_S_FEATURES_OK);
>>>   	status = dev->config->get_status(dev);
>>>   	if (!(status & VIRTIO_CONFIG_S_FEATURES_OK)) {
>>
>> Well don't you need to check it *before* VIRTIO_F_VERSION_1, not
after?
> 
> But it's only available with VERSION_1 anyway, isn't it? So it
probably
> also needs to fail when this feature is needed if VERSION_1 has not been
> negotiated, I think.
> 
Yes, clearly, I will add this.

Thanks,
Pierre

-- 
Pierre Morel
IBM Lab Boeblingen