Re: [PATCH v2 6/8] iommu/amd: Enhance domain_alloc_user() to allocate PASID capable domain

[Vasant Hegde <vasant.hegde@amd.com>]

Hi Kevin,


On 10/17/2024 11:41 AM, Tian, Kevin wrote:
>> From: Jason Gunthorpe <jgg@ziepe.ca>
>> Sent: Wednesday, October 16, 2024 11:29 PM
>>
>> On Wed, Oct 16, 2024 at 02:48:04AM +0000, Tian, Kevin wrote:
>>>> From: Jason Gunthorpe <jgg@ziepe.ca>
>>>> Sent: Tuesday, October 15, 2024 8:40 PM
>>>>
>>>> On Tue, Oct 15, 2024 at 08:41:48AM +0000, Tian, Kevin wrote:
>>>>
>>>>>> -	return do_iommu_domain_alloc(type, dev, flags,
>> AMD_IOMMU_V1);
>>>>>> +	/* Allocate v2 page table if IOMMU and device supports
>> PASID. */
>>>>>> +	if (flags & IOMMU_HWPT_ALLOC_PASID) {
>>>>>> +		if (!amd_iommu_pasid_supported() ||
>>>>>> +		    !pdev_pasid_supported(dev_data))
>>>>>> +			return ERR_PTR(-EINVAL);
>>>>>
>>>>> Just check the iommu capability here? IMHO it's a sane case to first
>>>>> create a PASID-compatible domain for a device which doesn't support
>>>>> PASID and then attach the domain to a PASID-capable device later.
>>>>
>>>> The point of this series is to allow AMD to select the v1 format as
>>>> often as possible because v1 has better performance than v2
>>>
>>> If the user wants better performance then it should not set the flag.
>>
>> Well, I do tend to agree with that, you mean remove the
>> pdev_pasid_supported() ?
>>
> 
> yes

Yeah. That should be fine I guess.  Will fix it.

-Vasant