linux-kernel - Re: [PATCH V3] vfio: platform: support No-IOMMU mode

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Date:	Sun, 12 Jun 2016 17:02:00 +0800
From:	Peng Fan <van.freenix@...il.com>
To:	eric.auger@...aro.org, b.reynal@...tualopensystems.com,
	alex.williamson@...hat.com
Cc:	kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V3] vfio: platform: support No-IOMMU mode

Hi,

Kindly ping.. Any comments on V3?

Thanks,
Peng.
On Mon, May 23, 2016 at 05:47:30PM +0800, Peng Fan wrote:
>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."
>
>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>
>---
>
>V3:
> The platform device can be programmed to do DMA without
> caring out mmap + VFIO_IOMMU_MAP_DMA which are not
> support by noiommu. So drop the last sentence of commit log
> in V2, which is misleading.
>
>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
>