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SubjectRe: [PATCH v3 1/1] s390: virtio: let arch accept devices without IOMMU feature
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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@linux.ibm.com>
>> Acked-by: Jason Wang <jasowang@redhat.com>
>> Acked-by: Christian Borntraeger <borntraeger@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

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