On 2020-06-10 16:53, Cornelia Huck wrote:

On Wed, 10 Jun 2020 16:37:55 +0200
Pierre Morel [off-list ref] wrote:

quoted

On 2020-06-10 15:24, Cornelia Huck wrote:

quoted

On Wed, 10 Jun 2020 15:11:51 +0200
Pierre Morel [off-list ref] wrote:
   

quoted

Protected Virtualisation protects the memory of the guest and
do not allow a the host to access all of its memory.

Let's refuse a VIRTIO device which does not use IOMMU
protected access.

Signed-off-by: Pierre Morel <redacted>
---
   drivers/s390/virtio/virtio_ccw.c | 5 +++++
   1 file changed, 5 insertions(+)

diff --git a/drivers/s390/virtio/virtio_ccw.c b/drivers/s390/virtio/virtio_ccw.c
index 5730572b52cd..06ffbc96587a 100644
--- a/drivers/s390/virtio/virtio_ccw.c
+++ b/drivers/s390/virtio/virtio_ccw.c

@@ -986,6 +986,11 @@ static void virtio_ccw_set_status(struct virtio_device *vdev, u8 status)
   	if (!ccw)
   		return;
   
+	/* Protected Virtualisation guest needs IOMMU */
+	if (is_prot_virt_guest() &&
+	    !__virtio_test_bit(vdev, VIRTIO_F_IOMMU_PLATFORM))
+			status &= ~VIRTIO_CONFIG_S_FEATURES_OK;
+

set_status seems like an odd place to look at features; shouldn't that
rather be done in finalize_features?

Right, looks better to me too.
What about:

diff --git a/drivers/s390/virtio/virtio_ccw.c

b/drivers/s390/virtio/virtio_ccw.c
index 06ffbc96587a..227676297ea0 100644

--- a/drivers/s390/virtio/virtio_ccw.c
+++ b/drivers/s390/virtio/virtio_ccw.c

@@ -833,6 +833,11 @@ static int virtio_ccw_finalize_features(struct

virtio_device *vdev)
                  ret = -ENOMEM;
                  goto out_free;
          }
+
+       if (is_prot_virt_guest() &&
+           !__virtio_test_bit(vdev, VIRTIO_F_IOMMU_PLATFORM))

Add a comment, and (maybe) a message?

Otherwise, I think this is fine, as it should fail the probe, which is
what we want.

yes right a message is needed.
and I extend a little the comment I had before.
thanks

Regards,
Pierre

-- 
Pierre Morel
IBM Lab Boeblingen