Re: [PATCH v1 5/8] iommu/amd: Use iommu_attach/detach_device()

[Lu Baolu]

Hi Jason,

On 1/6/22 10:33 PM, Jason Gunthorpe wrote:
> On Thu, Jan 06, 2022 at 10:20:50AM +0800, Lu Baolu wrote:
> > The individual device driver should use iommu_attach/detach_device()
> > for domain attachment/detachment.
> >
> > Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
> >   drivers/iommu/amd/iommu_v2.c | 4 ++--
> >   1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/iommu/amd/iommu_v2.c b/drivers/iommu/amd/iommu_v2.c
> > index 58da08cc3d01..7d9d0fe89064 100644
> > +++ b/drivers/iommu/amd/iommu_v2.c
> > @@ -133,7 +133,7 @@ static void free_device_state(struct device_state *dev_state)
> >   	if (WARN_ON(!group))
> >   		return;
> >   
> > -	iommu_detach_group(dev_state->domain, group);
> > +	iommu_detach_device(dev_state->domain, &dev_state->pdev->dev);
> >   
> >   	iommu_group_put(group);
>
> This is the only user of the group in the function all the
> group_get/put should be deleted too.
>
> Joerg said in commit 55c99a4dc50f ("iommu/amd: Use
> iommu_attach_group()") that the device API doesn't work here because
> there are multi-device groups?
>
> But I'm not sure how this can work with multi-device groups - this
> seems to assigns a domain setup for direct map, so perhaps this only
> works if all devices are setup for direct map?

It's also difficult for me to understand how this can work with multi-
device group. The iommu_attach_group() returns -EBUSY if _init_device()
is called for the second device in the group. That's the reason why I
didn't set no_kernel_dma.

> > @@ -791,7 +791,7 @@ int amd_iommu_init_device(struct pci_dev *pdev, int pasids)
> >   		goto out_free_domain;
> >   	}
> >   
> > -	ret = iommu_attach_group(dev_state->domain, group);
> > +	ret = iommu_attach_device(dev_state->domain, &pdev->dev);
> >   	if (ret != 0)
> >   		goto out_drop_group;
>
> Same comment here

Yes.

> Jason

Best regards,
baolu