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

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Date:	Thu, 23 Jun 2016 13:05:15 -0600
From:	Alex Williamson <alex.williamson@...hat.com>
To:	Peng Fan <van.freenix@...il.com>
Cc:	eric.auger@...aro.org, b.reynal@...tualopensystems.com,
	kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V3] vfio: platform: support No-IOMMU mode

On Sun, 12 Jun 2016 17:02:00 +0800
Peng Fan <van.freenix@...il.com> wrote:

> 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>
> >---

Applied with Eric's R-b to next branch for v4.8.  Thanks!

Alex

> >
> >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
> >