[PATCH v8 1/2] virtio: let arch validate VIRTIO features

[Pierre Morel]

An architecture may need to validate the VIRTIO devices features
based on architecture specifics.

Provide a new Kconfig entry, CONFIG_ARCH_HAS_RESTRICTED_MEMORY_ACCESS,
the architecture can select when it provides a callback named
arch_has_restricted_memory_access to validate the virtio device
features.

Signed-off-by: Pierre Morel <pmorel@xxxxxxxxxxxxx>
---
 drivers/virtio/Kconfig        | 6 ++++++
 drivers/virtio/virtio.c       | 4 ++++
 include/linux/virtio_config.h | 9 +++++++++
 3 files changed, 19 insertions(+)

diff --git a/drivers/virtio/Kconfig b/drivers/virtio/Kconfig
index 5809e5f5b157..eef09e3c92f9 100644
--- a/drivers/virtio/Kconfig
+++ b/drivers/virtio/Kconfig
@@ -6,6 +6,12 @@ config VIRTIO
 	  bus, such as CONFIG_VIRTIO_PCI, CONFIG_VIRTIO_MMIO, CONFIG_RPMSG
 	  or CONFIG_S390_GUEST.
 
+config ARCH_HAS_RESTRICTED_MEMORY_ACCESS
+	bool
+	help
+	  This option is selected by any architecture enforcing
+	  VIRTIO_F_IOMMU_PLATFORM
+
 menuconfig VIRTIO_MENU
 	bool "Virtio drivers"
 	default y
diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
index a977e32a88f2..1471db7d6510 100644
--- a/drivers/virtio/virtio.c
+++ b/drivers/virtio/virtio.c
@@ -176,6 +176,10 @@ int virtio_finalize_features(struct virtio_device *dev)
 	if (ret)
 		return ret;
 
+	ret = arch_has_restricted_memory_access(dev);
+	if (ret)
+		return ret;
+
 	if (!virtio_has_feature(dev, VIRTIO_F_VERSION_1))
 		return 0;
 
diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h
index bb4cc4910750..f6b82541c497 100644
--- a/include/linux/virtio_config.h
+++ b/include/linux/virtio_config.h
@@ -459,4 +459,13 @@ static inline void virtio_cwrite64(struct virtio_device *vdev,
 		_r;							\
 	})
 
+#ifdef CONFIG_ARCH_HAS_RESTRICTED_MEMORY_ACCESS
+int arch_has_restricted_memory_access(struct virtio_device *dev);
+#else
+static inline int arch_has_restricted_memory_access(struct virtio_device *dev)
+{
+	return 0;
+}
+#endif /* CONFIG_ARCH_HAS_RESTRICTED_MEMORY_ACCESS */
+
 #endif /* _LINUX_VIRTIO_CONFIG_H */
-- 
2.25.1