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

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Date:	Fri, 20 May 2016 17:56:59 +0800
From:	Peng Fan <van.freenix@...il.com>
To:	Eric Auger <eric.auger@...aro.org>
Cc:	Baptiste Reynal <b.reynal@...tualopensystems.com>,
	Alex Williamson <alex.williamson@...hat.com>,
	"open list:VFIO DRIVER" <kvm@...r.kernel.org>,
	open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] vfio: platform: use vfio_iommu_group_get/put

Hi Eric,

On Fri, May 20, 2016 at 11:22:13AM +0200, Eric Auger wrote:
>Hi Peng,
>On 05/20/2016 10:36 AM, Peng Fan wrote:
>> Hi,
>> 
>> On Fri, May 20, 2016 at 10:20:32AM +0200, Baptiste Reynal wrote:
>>> Hi,
>>>
>>> On Fri, May 20, 2016 at 9:58 AM, Eric Auger <eric.auger@...aro.org> wrote:
>>>>
>>>> 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.
>> 
>> Yeah. Initially I would like to try vfio on my i.MX6/7 boards which does not
>> have HW iommu. I am new to this, so just wrote this simple patch when I was
>> reading the source code.
>> 
>>>
>>> Since safety issues have already been addressed for the PCI patch
>>> series, I don't see any reason not to enable it. You might extend the
>>> commit message to remind those issues.
>> 
>> Eric, Baptiste,
>> 
>> Is vfio-platform no-iommu on your TODO list? I am happy to help test.
>> If not, I can try work on this if you could guide me -:)
>No it is not at the moment. shouldn't it work already with this very
>patch? I will be happy to bring support to you if needed.

This patch was code inspection work. Since it did not break vfio-platform
iommu, I sent it out. I have not played well with userspace test
code/step or qemu (:

Is it ok for me to test vfio-platform no-iommu using a platform device
withou DMA capability, such as simple UART?

If it's ok, I'll follow the test code[1] to write my test code and do some test.

Regards,
Peng.

[1] https://github.com/virtualopensystems/vfio-host-test/tree/master/src_test

>
>Best Regards
>
>Eric
>> 
>> Thanks,
>> Peng.
>>>
>>> Best regards,
>>> Baptiste
>>>
>>>>
>>>> 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;
>>>>>>>
>>>>>
>>>>
>