linux-kernel - [PATCH] s390: protvirt: virtio: Refuse device without IOMMU

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Date:   Wed, 10 Jun 2020 15:11:51 +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] s390: protvirt: virtio: Refuse device without IOMMU

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 <pmorel@...ux.ibm.com>
---
 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;
+
 	/* Write the status to the host. */
 	vcdev->dma_area->status = status;
 	ccw->cmd_code = CCW_CMD_WRITE_STATUS;
-- 
2.25.1