Re: [PATCH v6 07/33] iommu: Avoid reallocate default domain for a group

Yong Wu
2021-01-27T09:42:50Z

On Tue, 2021-01-26 at 22:23 +0000, Will Deacon wrote:
> On Mon, Jan 11, 2021 at 07:18:48PM +0800, Yong Wu wrote:
> > If group->default_domain exists, avoid reallocate it.
> >
> > In some iommu drivers, there may be several devices share a group. Avoid
> > realloc the default domain for this case.
> >
> > Signed-off-by: Yong Wu <yong.wu@mediatek.com>
> > ---
> > drivers/iommu/iommu.c | 3 ++-
> > 1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> > index 3d099a31ddca..f4b87e6abe80 100644
> > --- a/drivers/iommu/iommu.c
> > +++ b/drivers/iommu/iommu.c
> > @@ -266,7 +266,8 @@ int iommu_probe_device(struct device *dev)
> > * support default domains, so the return value is not yet
> > * checked.
> > */
> > - iommu_alloc_default_domain(group, dev);
> > + if (!group->default_domain)
> > + iommu_alloc_default_domain(group, dev);
>
> I don't really get what this achieves, since iommu_alloc_default_domain()
> looks like this:
>
> static int iommu_alloc_default_domain(struct iommu_group *group,
> struct device *dev)
> {
> unsigned int type;
>
> if (group->default_domain)
> return 0;
>
> ...
>
> in which case, it should be fine?

oh. sorry, I overlooked this. the current code is enough.
I will remove this patch. and send the next version in this week.
Thanks very much.

>
> Will