linux-kernel - [PATCH v1 1/1] s390: virtio-ccw: PV needs VIRTIO I/O device protection

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Date:   Thu,  6 Aug 2020 16:23:02 +0200
From:   Pierre Morel <pmorel@...ux.ibm.com>
To:     linux-kernel@...r.kernel.org
Cc:     pasic@...ux.ibm.com, borntraeger@...ibm.com, frankja@...ux.ibm.com,
        mst@...hat.com, jasowang@...hat.com, cohuck@...hat.com,
        kvm@...r.kernel.org, linux-s390@...r.kernel.org,
        virtualization@...ts.linux-foundation.org
Subject: [PATCH v1 1/1] s390: virtio-ccw: PV needs VIRTIO I/O device protection

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 ccw_transport_features() to fail feature negociation
and consequently probe if that's not the case, preventing a host
error on access attempt.

Signed-off-by: Pierre Morel <pmorel@...ux.ibm.com>
---
 drivers/s390/virtio/virtio_ccw.c | 24 +++++++++++++++++++-----
 1 file changed, 19 insertions(+), 5 deletions(-)

diff --git a/drivers/s390/virtio/virtio_ccw.c b/drivers/s390/virtio/virtio_ccw.c
index 5730572b52cd..cc8d8064c6c4 100644
--- a/drivers/s390/virtio/virtio_ccw.c
+++ b/drivers/s390/virtio/virtio_ccw.c
@@ -803,11 +803,23 @@ static u64 virtio_ccw_get_features(struct virtio_device *vdev)
 	return rc;
 }
 
-static void ccw_transport_features(struct virtio_device *vdev)
+static int ccw_transport_features(struct virtio_device *vdev)
 {
-	/*
-	 * Currently nothing to do here.
-	 */
+	if (!is_prot_virt_guest())
+		return 0;
+
+	if (!virtio_has_feature(vdev, VIRTIO_F_VERSION_1)) {
+		dev_warn(&vdev->dev,
+			 "device must provide VIRTIO_F_VERSION_1\n");
+		return -ENODEV;
+	}
+
+	if (!virtio_has_feature(vdev, VIRTIO_F_IOMMU_PLATFORM)) {
+		dev_warn(&vdev->dev,
+			 "device must provide VIRTIO_F_IOMMU_PLATFORM\n");
+		return -ENODEV;
+	}
+	return 0;
 }
 
 static int virtio_ccw_finalize_features(struct virtio_device *vdev)
@@ -837,7 +849,9 @@ static int virtio_ccw_finalize_features(struct virtio_device *vdev)
 	vring_transport_features(vdev);
 
 	/* Give virtio_ccw a chance to accept features. */
-	ccw_transport_features(vdev);
+	ret = ccw_transport_features(vdev);
+	if (ret)
+		goto out_free;
 
 	features->index = 0;
 	features->features = cpu_to_le32((u32)vdev->features);
-- 
2.25.1