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

Robin Murphy
2021-01-29T00:05:08Z

On 2021-01-28 21:14, Will Deacon wrote:
> On Thu, Jan 28, 2021 at 09:10:20PM +0000, Will Deacon wrote:
>> On Wed, Jan 27, 2021 at 05:39:16PM +0800, Yong Wu wrote:
>>> 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.
>>
>> Actually, looking at this again, if we're dropping this patch and patch 6
>> just needs the kfree() moving about, then there's no need to repost. The
>> issue that Robin and Paul are discussing can be handled separately.

FWIW patch #6 gets dropped as well now, since Rob has applied the
standalone fix (89c7cb1608ac).

Robin.

> Argh, except that this version of the patches doesn't apply :)
>
> So after all that, please go ahead and post a v7 ASAP based on this branch:
>
> https://git.kernel.org/pub/scm/linux/kernel/git/will/linux.git/log/?h=for-joerg/mtk
>
> Will
>