Re: [PATCH v12 07/17] iommu: Try to allocate blocking domain when probing device

[Baolu Lu <baolu.lu@linux.intel.com>]

On 2022/8/26 22:52, Jason Gunthorpe wrote:
> On Fri, Aug 26, 2022 at 08:11:31PM +0800, Lu Baolu wrote:
>> Allocate the blocking domain when probing devices if the driver supports
>> blocking domain allocation. Otherwise, revert to the previous behavior,
>> that is, use UNMANAGED domain instead when the blocking domain is needed.
>>
>> Signed-off-by: Lu Baolu<baolu.lu@linux.intel.com>
>> Tested-by: Zhangfei Gao<zhangfei.gao@linaro.org>
>> Tested-by: Tony Zhu<tony.zhu@intel.com>
>> ---
>>   drivers/iommu/iommu.c | 29 +++++++++++++++++------------
>>   1 file changed, 17 insertions(+), 12 deletions(-)
> This seems like a lot of overhead to allocate these things for every
> group?
> 
> Why not add a simple refcount on the blocking domain instead and
> allocate the domain on the pasid attach like we do for ownership?

I am working towards implementing static instance of blocking domain for
each IOMMU driver, and then, there's no much overhead to allocate it in
the probing device path.

Best regards,
baolu