vfio: Support VFIO_NOIOMMU with iommufd

Add a small amount of emulation to vfio_compat to accept the SET_IOMMU to
VFIO_NOIOMMU_IOMMU and have vfio just ignore iommufd if it is working on a
no-iommu enabled device.

Move the enable_unsafe_noiommu_mode module out of container.c into
vfio_main.c so that it is always available even if VFIO_CONTAINER=n.

This passes Alex's mini-test:

https://github.com/awilliam/tests/blob/master/vfio-noiommu-pci-device-open.c

Link: https://lore.kernel.org/r/0-v3-480cd64a16f7+1ad0-iommufd_noiommu_jgg@nvidia.com
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Acked-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

6 files changed, 38 insertions, 12 deletions

diff --git a/drivers/vfio/Kconfig b/drivers/vfio/Kconfig
index a8f544629467..89e06c981e43 100644
--- a/drivers/vfio/Kconfig
+++ b/drivers/vfio/Kconfig
@@ -32,6 +32,7 @@ config VFIO_IOMMU_SPAPR_TCE
 	tristate
 	depends on SPAPR_TCE_IOMMU
 	default VFIO
+endif
 
 config VFIO_NOIOMMU
 	bool "VFIO No-IOMMU support"
@@ -46,7 +47,6 @@ config VFIO_NOIOMMU
 	  this mode since there is no IOMMU to provide DMA translation.
 
 	  If you don't know what to do here, say N.
-endif
 
 config VFIO_VIRQFD
 	bool
diff --git a/drivers/vfio/container.c b/drivers/vfio/container.c
index b7a9560ab25e..89f10becf962 100644
--- a/drivers/vfio/container.c
+++ b/drivers/vfio/container.c
@@ -29,13 +29,6 @@ static struct vfio {
 	struct mutex			iommu_drivers_lock;
 } vfio;
 
-#ifdef CONFIG_VFIO_NOIOMMU
-bool vfio_noiommu __read_mostly;
-module_param_named(enable_unsafe_noiommu_mode,
-		   vfio_noiommu, bool, S_IRUGO | S_IWUSR);
-MODULE_PARM_DESC(enable_unsafe_noiommu_mode, "Enable UNSAFE, no-IOMMU mode.  This mode provides no device isolation, no DMA translation, no host kernel protection, cannot be used for device assignment to virtual machines, requires RAWIO permissions, and will taint the kernel.  If you do not know what this is for, step away. (default: false)");
-#endif
-
 static void *vfio_noiommu_open(unsigned long arg)
 {
 	if (arg != VFIO_NOIOMMU_IOMMU)
diff --git a/drivers/vfio/group.c b/drivers/vfio/group.c
index bb24b2f0271e..e166ad7ce6e7 100644
--- a/drivers/vfio/group.c
+++ b/drivers/vfio/group.c
@@ -133,9 +133,12 @@ static int vfio_group_ioctl_set_container(struct vfio_group *group,
 
 	iommufd = iommufd_ctx_from_file(f.file);
 	if (!IS_ERR(iommufd)) {
-		u32 ioas_id;
+		if (IS_ENABLED(CONFIG_VFIO_NOIOMMU) &&
+		    group->type == VFIO_NO_IOMMU)
+			ret = iommufd_vfio_compat_set_no_iommu(iommufd);
+		else
+			ret = iommufd_vfio_compat_ioas_create(iommufd);
 
-		ret = iommufd_vfio_compat_ioas_id(iommufd, &ioas_id);
 		if (ret) {
 			iommufd_ctx_put(group->iommufd);
 			goto out_unlock;
diff --git a/drivers/vfio/iommufd.c b/drivers/vfio/iommufd.c
index 4f82a6fa7c6c..db4efbd56042 100644
--- a/drivers/vfio/iommufd.c
+++ b/drivers/vfio/iommufd.c
@@ -18,6 +18,20 @@ int vfio_iommufd_bind(struct vfio_device *vdev, struct iommufd_ctx *ictx)
 
 	lockdep_assert_held(&vdev->dev_set->lock);
 
+	if (vfio_device_is_noiommu(vdev)) {
+		if (!capable(CAP_SYS_RAWIO))
+			return -EPERM;
+
+		/*
+		 * Require no compat ioas to be assigned to proceed. The basic
+		 * statement is that the user cannot have done something that
+		 * implies they expected translation to exist
+		 */
+		if (!iommufd_vfio_compat_ioas_get_id(ictx, &ioas_id))
+			return -EPERM;
+		return 0;
+	}
+
 	/*
 	 * If the driver doesn't provide this op then it means the device does
 	 * not do DMA at all. So nothing to do.
@@ -29,7 +43,7 @@ int vfio_iommufd_bind(struct vfio_device *vdev, struct iommufd_ctx *ictx)
 	if (ret)
 		return ret;
 
-	ret = iommufd_vfio_compat_ioas_id(ictx, &ioas_id);
+	ret = iommufd_vfio_compat_ioas_get_id(ictx, &ioas_id);
 	if (ret)
 		goto err_unbind;
 	ret = vdev->ops->attach_ioas(vdev, &ioas_id);
@@ -52,6 +66,9 @@ void vfio_iommufd_unbind(struct vfio_device *vdev)
 {
 	lockdep_assert_held(&vdev->dev_set->lock);
 
+	if (vfio_device_is_noiommu(vdev))
+		return;
+
 	if (vdev->ops->unbind_iommufd)
 		vdev->ops->unbind_iommufd(vdev);
 }
diff --git a/drivers/vfio/vfio.h b/drivers/vfio/vfio.h
index f8219a438bfb..9e94abcf8ee1 100644
--- a/drivers/vfio/vfio.h
+++ b/drivers/vfio/vfio.h
@@ -10,10 +10,10 @@
 #include <linux/device.h>
 #include <linux/cdev.h>
 #include <linux/module.h>
+#include <linux/vfio.h>
 
 struct iommufd_ctx;
 struct iommu_group;
-struct vfio_device;
 struct vfio_container;
 
 void vfio_device_put_registration(struct vfio_device *device);
@@ -88,6 +88,12 @@ bool vfio_device_has_container(struct vfio_device *device);
 int __init vfio_group_init(void);
 void vfio_group_cleanup(void);
 
+static inline bool vfio_device_is_noiommu(struct vfio_device *vdev)
+{
+	return IS_ENABLED(CONFIG_VFIO_NOIOMMU) &&
+	       vdev->group->type == VFIO_NO_IOMMU;
+}
+
 #if IS_ENABLED(CONFIG_VFIO_CONTAINER)
 /* events for the backend driver notify callback */
 enum vfio_iommu_notify_type {
diff --git a/drivers/vfio/vfio_main.c b/drivers/vfio/vfio_main.c
index 5177bb061b17..90541fc94988 100644
--- a/drivers/vfio/vfio_main.c
+++ b/drivers/vfio/vfio_main.c
@@ -45,6 +45,13 @@ static struct vfio {
 	struct ida			device_ida;
 } vfio;
 
+#ifdef CONFIG_VFIO_NOIOMMU
+bool vfio_noiommu __read_mostly;
+module_param_named(enable_unsafe_noiommu_mode,
+		   vfio_noiommu, bool, S_IRUGO | S_IWUSR);
+MODULE_PARM_DESC(enable_unsafe_noiommu_mode, "Enable UNSAFE, no-IOMMU mode.  This mode provides no device isolation, no DMA translation, no host kernel protection, cannot be used for device assignment to virtual machines, requires RAWIO permissions, and will taint the kernel.  If you do not know what this is for, step away. (default: false)");
+#endif
+
 static DEFINE_XARRAY(vfio_device_set_xa);
 
 int vfio_assign_device_set(struct vfio_device *device, void *set_id)