linux-kernel - Re: [PATCH] vfio: platform: use vfio_iommu_group

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Date:	Fri, 20 May 2016 09:58:32 +0200
From:	Eric Auger <eric.auger@...aro.org>
To:	Alex Williamson <alex.williamson@...hat.com>,
	Peng Fan <van.freenix@...il.com>
Cc:	b.reynal@...tualopensystems.com, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] vfio: platform: use vfio_iommu_group_get/put

Hi,
On 05/19/2016 11:01 PM, Alex Williamson wrote:
> On Tue, 10 May 2016 15:40:28 +0800
> Peng Fan <van.freenix@...il.com> wrote:
> 
>> Hi Alex,
>>
>> On Mon, May 09, 2016 at 09:32:38AM -0600, Alex Williamson wrote:
>>> On Mon,  9 May 2016 18:01:43 +0800
>>> Peng Fan <van.freenix@...il.com> wrote:
>>>  
>>>> Use vfio_iommu_group_get and vfio_iommu_group_put, but not
>>>> iommu_group_get or iommu_group_put.  
>>>
>>> I assume you're trying to duplicate the vfio_pci changes from commit
>>> 03a76b60f8ba to enable no-iommu mode.  That would be really relevant
>>> information for the commit log.  
>>
>> This is not to support non-iommu for vfio platform. I just think
>> vfio_iommu_group_get/put is vfio core API and should be used by
>> vfio-pci and vfio-platform.
> 
> Hi Peng,
> 
> I suppose I would consider this an optional part of the internal vfio
> API, it's only real purpose it to provide the ability to create fake
> groups which are only used for no-iommu.  It's perfectly legitimate to
> use iommu_group_get/put if there is no desire to enable no-iommu.
> Baptiste, Eric, do you have an opinion whether enabling no-iommu in
> vfio/platform is something we should do?  Thanks,
I think it would make sense to introduce that no-iommu feature for
vfio-platform because it allows potential users to get familiar with
VFIO platform without having the proper HW. I also thought the primary
purpose of this patch was to introduce that support.

Best Regards

Eric
> 
> Alex
> 
>>>>
>>>> Signed-off-by: Peng Fan <van.freenix@...il.com>
>>>> Cc: Baptiste Reynal <b.reynal@...tualopensystems.com>
>>>> Cc: Alex Williamson <alex.williamson@...hat.com>
>>>> ---
>>>>  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..582885e 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);
>>>>  		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;  
>>>  
>