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

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Message-ID: <d62cedeb-1f57-25cd-d9f1-67ff5dd7ef16@redhat.com>
Date:	Mon, 13 Jun 2016 15:20:39 +0200
From:	Auger Eric <eric.auger@...hat.com>
To:	Peng Fan <van.freenix@...il.com>, 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 Peng
Le 23/05/2016 à 11:47, Peng Fan a écrit :
> 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>
Looks good to me.
Reviewed-by: Eric Auger <eric.auger@...hat.com>

as a reminder may conflict with HiDma ACPI reset series.

Best Regards

Eric


> ---
> 
> 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;
>