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From:   Pierre Morel <pmorel@linux.ibm.com>
To:     linux-kernel@vger.kernel.org
Cc:     pasic@linux.ibm.com, borntraeger@de.ibm.com, frankja@linux.ibm.com,
        mst@redhat.com, jasowang@redhat.com, cohuck@redhat.com,
        kvm@vger.kernel.org, linux-s390@vger.kernel.org,
        virtualization@lists.linux-foundation.org, thomas.lendacky@amd.com,
        david@gibson.dropbear.id.au, linuxram@us.ibm.com,
        hca@linux.ibm.com, gor@linux.ibm.com
Subject: [PATCH v7 2/2] s390: virtio: PV needs VIRTIO I/O device protection
Date:   Wed, 15 Jul 2020 10:31:09 +0200
Message-Id: <1594801869-13365-3-git-send-email-pmorel@linux.ibm.com>
In-Reply-To: <1594801869-13365-1-git-send-email-pmorel@linux.ibm.com>
References: <1594801869-13365-1-git-send-email-pmorel@linux.ibm.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

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@linux.ibm.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Acked-by: Halil Pasic <pasic@linux.ibm.com>
Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
---
 arch/s390/mm/init.c | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c
index 6dc7c3b60ef6..d39af6554d4f 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 +162,33 @@ 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,
+			 "legacy virtio not supported with protected virtualization\n");
+		return -ENODEV;
+	}
+
+	if (!virtio_has_feature(dev, VIRTIO_F_IOMMU_PLATFORM)) {
+		dev_warn(&dev->dev,
+			 "support for limited memory access required for protected virtualization\n");
+		return -ENODEV;
+	}
+
+	return 0;
+}
+
 /* protected virtualization */
 static void pv_init(void)
 {
-- 
2.25.1