Linux Virtualization - Jul 2020 - [PATCH v5 2/2] s390: virtio: PV needs VIRTIO I/O device protection

On Thu,  9 Jul 2020 10:39:19 +0200
Pierre Morel <pmorel at 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 at 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.
> +		return -ENODEV;
> +	}
> +
> +	return 0;
> +}
> +
>  /* protected virtualization */
>  static void pv_init(void)
>  {
Either way,

Reviewed-by: Cornelia Huck <cohuck at redhat.com>

On Thu, 9 Jul 2020 10:57:33 +0200
Cornelia Huck <cohuck at redhat.com> wrote:
> On Thu,  9 Jul 2020 10:39:19 +0200
> Pierre Morel <pmorel at 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
Punctuation at the end?

Also 'that's not the case' refers to the negation
'VIRTIO_F_IOMMU_PLATFORM has been negotiated',
arch_validate_virtio_features() is however part of
virtio_finalize_features(), which is in turn part of the feature
negotiation. But that is details. I'm fine with keeping the message as
is. 
> > 
> > Signed-off-by: Pierre Morel <pmorel at 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.
I liked the messages in v4. Why did we change those? Did somebody
complain?

I prefer the old ones, but it any case:

Acked-by: Halil Pasic <pasic at linux.ibm.com>

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

On 2020-07-09 10:57, Cornelia Huck wrote:
> On Thu,  9 Jul 2020 10:39:19 +0200
> Pierre Morel <pmorel at 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 at 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 at redhat.com>
> 
Thanks,
Pierre


-- 
Pierre Morel
IBM Lab Boeblingen

On 2020-07-09 11:55, Halil Pasic wrote:
> On Thu, 9 Jul 2020 10:57:33 +0200
> Cornelia Huck <cohuck at redhat.com> wrote:
> 
>> On Thu,  9 Jul 2020 10:39:19 +0200
>> Pierre Morel <pmorel at 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
> 
> Punctuation at the end?
> 
> Also 'that's not the case' refers to the negation
> 'VIRTIO_F_IOMMU_PLATFORM has been negotiated',
> arch_validate_virtio_features() is however part of
> virtio_finalize_features(), which is in turn part of the feature
> negotiation. But that is details. I'm fine with keeping the message as
> is.
> 
>>>
>>> Signed-off-by: Pierre Morel <pmorel at 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.
> 
> I liked the messages in v4. Why did we change those? Did somebody
> complain?
> 
> I prefer the old ones, but it any case:
> 
> Acked-by: Halil Pasic <pasic at linux.ibm.com>
Thanks,
Pierre


-- 
Pierre Morel
IBM Lab Boeblingen

On Thu, 9 Jul 2020 12:51:58 +0200
Pierre Morel <pmorel at linux.ibm.com> wrote:
> >> +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.
Not all our end users are kernel and/or qemu developers. I find the
messages from v4 less technical, more informative, and way better.

Regards,
Halil