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

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

On 2020-07-02 15:03, Pierre Morel wrote:
> 
> 
> 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.

would be something like:

-       if (!virtio_has_feature(dev, VIRTIO_F_VERSION_1))
-               return 0;
+       if (!virtio_has_feature(dev, VIRTIO_F_VERSION_1)) {
+               ret = arch_accept_virtio_features(dev);
+               if (ret)
+                       dev_warn(&dev->dev,
+                                "virtio: device must provide 
VIRTIO_F_VERSION_1\n");
+               return ret;
+       }


just a thought on the function name:
It becomes more general than just IOMMU_PLATFORM related.

What do you think of:

arch_accept_virtio_features()

?

Regards,
Pierre


-- 
Pierre Morel
IBM Lab Boeblingen

On Mon, 6 Jul 2020 15:37:37 +0200
Pierre Morel <pmorel at linux.ibm.com> wrote:
> On 2020-07-02 15:03, Pierre Morel wrote:
> > 
> > 
> > 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.  
> 
> 
> would be something like:
> 
> -       if (!virtio_has_feature(dev, VIRTIO_F_VERSION_1))
> -               return 0;
> +       if (!virtio_has_feature(dev, VIRTIO_F_VERSION_1)) {
> +               ret = arch_accept_virtio_features(dev);
> +               if (ret)
> +                       dev_warn(&dev->dev,
> +                                "virtio: device must provide 
> VIRTIO_F_VERSION_1\n");
> +               return ret;
> +       }
That looks wrong; I think we want to validate in all cases. What about:

ret = arch_accept_virtio_features(dev); // this can include checking for
                                        // older or newer features
if (ret)
	// assume that the arch callback moaned already
	return ret;

if (!virtio_has_feature(dev, VIRTIO_F_VERSION_1))
	return 0;

// do the virtio-1 only FEATURES_OK dance
> 
> 
> just a thought on the function name:
> It becomes more general than just IOMMU_PLATFORM related.
> 
> What do you think of:
> 
> arch_accept_virtio_features()
Or maybe arch_validate_virtio_features()?
> 
> ?
> 
> Regards,
> Pierre
> 
>