[PATCH v3 1/1] s390: virtio: let arch accept devices without IOMMU feature

Pierre Morel
2020-06-17T10:44:16Z

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)) {
diff --git a/include/linux/virtio.h b/include/linux/virtio.h
index a493eac08393..e8526ae3463e 100644
--- a/include/linux/virtio.h
+++ b/include/linux/virtio.h
@@ -195,4 +195,6 @@ void unregister_virtio_driver(struct virtio_driver *drv);
#define module_virtio_driver(__virtio_driver) \
module_driver(__virtio_driver, register_virtio_driver, \
unregister_virtio_driver)
+
+int arch_needs_virtio_iommu_platform(struct virtio_device *dev);
#endif /* _LINUX_VIRTIO_H */
--
2.25.1