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

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Date:	Fri, 20 May 2016 10:20:32 +0200
From:	Baptiste Reynal <b.reynal@...tualopensystems.com>
To:	Eric Auger <eric.auger@...aro.org>
Cc:	Alex Williamson <alex.williamson@...hat.com>,
	Peng Fan <van.freenix@...il.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,

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.

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.

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;
> >>>
> >
>