linux-kernel - [PATCH V2] vfio: platform: support No-IOMMU mode

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Message-Id: <1463991250-980-1-git-send-email-van.freenix@gmail.com>
Date:	Mon, 23 May 2016 16:14:10 +0800
From:	Peng Fan <van.freenix@...il.com>
To:	alex.williamson@...hat.com, b.reynal@...tualopensystems.com,
	eric.auger@...aro.org
Cc:	kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
	Peng Fan <van.freenix@...il.com>
Subject: [PATCH V2] vfio: platform: support No-IOMMU mode

The vfio No-IOMMU mode was supported by this
'commit 03a76b60f8ba2797 ("vfio: Include No-IOMMU mode")',
but it only support vfio-pci.

Using vfio_iommu_group_get/put, but not iommu_group_get/put,
the platform devices can be exposed to userspace with
CONFIG_VFIO_NOIOMMU and the "enable_unsafe_noiommu_mode"
option enabled.

>From 'commit 03a76b60f8ba2797 ("vfio: Include No-IOMMU mode")',
"This should make it very clear that this mode is not safe.
Additionally, CAP_SYS_RAWIO privileges are necessary to work
with groups and containers using this mode.  Groups making
use of this support are named /dev/vfio/noiommu-$GROUP and
can only make use of the special VFIO_NOIOMMU_IOMMU for the
container.  Use of this mode, specifically binding a device
without a native IOMMU group to a VFIO bus driver will taint
the kernel and should therefore not be considered supported.",

Actually, for vfio-platform No-IOMMU mode, the userspace can
not do DMA, because the ioctl API of noiommu container only
supports VFIO_CHECK_EXTENSION and VFIO_IOMMU_MAP_DMA is not
supported.

Signed-off-by: Peng Fan <van.freenix@...il.com>
Cc: Eric Auger <eric.auger@...aro.org>
Cc: Baptiste Reynal <b.reynal@...tualopensystems.com>
Cc: Alex Williamson <alex.williamson@...hat.com>
---

V2:
 Rename subject to support No-IOMMU
 Add more commit log.

 I wrote a simple program following this
 https://github.com/virtualopensystems/vfio-host-test/blob/master/src_test/vfio_device_test.c
 ,no dma support. The device's register can be
 accessed in userspace using command './vfio_dev_test 30b60000.usdhc 0 1 platform'

 drivers/vfio/platform/vfio_platform_common.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/vfio/platform/vfio_platform_common.c b/drivers/vfio/platform/vfio_platform_common.c
index e65b142..993b2f9 100644
--- a/drivers/vfio/platform/vfio_platform_common.c
+++ b/drivers/vfio/platform/vfio_platform_common.c
@@ -561,7 +561,7 @@ int vfio_platform_probe_common(struct vfio_platform_device *vdev,
 
 	vdev->device = dev;
 
-	group = iommu_group_get(dev);
+	group = vfio_iommu_group_get(dev);
 	if (!group) {
 		pr_err("VFIO: No IOMMU group for device %s\n", vdev->name);
 		return -EINVAL;
@@ -569,7 +569,7 @@ int vfio_platform_probe_common(struct vfio_platform_device *vdev,
 
 	ret = vfio_add_group_dev(dev, &vfio_platform_ops, vdev);
 	if (ret) {
-		iommu_group_put(group);
+		vfio_iommu_group_put(group, dev);
 		return ret;
 	}
 
@@ -589,7 +589,7 @@ struct vfio_platform_device *vfio_platform_remove_common(struct device *dev)
 
 	if (vdev) {
 		vfio_platform_put_reset(vdev);
-		iommu_group_put(dev->iommu_group);
+		vfio_iommu_group_put(dev->iommu_group, dev);
 	}
 
 	return vdev;
-- 
2.6.2