Re: [PATCH] vfio: platform: use vfio_iommu_group_get/put

[Eric Auger]

Hi Peng,
On 05/20/2016 11:56 AM, Peng Fan wrote:
> 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@xxxxxxxxxx> 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@xxxxxxxxx> 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@xxxxxxxxx> 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?

My feeling is that it is a reasonable start.

Best Regards

Eric
> 
> 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@xxxxxxxxx>
>>>>>>>>> Cc: Baptiste Reynal <b.reynal@xxxxxxxxxxxxxxxxxxxxxx>
>>>>>>>>> Cc: Alex Williamson <alex.williamson@xxxxxxxxxx>
>>>>>>>>> ---
>>>>>>>>>  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;
>>>>>>>>
>>>>>>
>>>>>
>>