Re: [PATCH v2 09/12] iommu/amd: Add support for nest parent domain allocation

["Suthikulpanit, Suravee" <suravee.suthikulpanit@amd.com>]

On 10/2/2025 1:00 PM, Nicolin Chen wrote:
> On Wed, Oct 01, 2025 at 06:09:51AM +0000, Suravee Suthikulpanit wrote:
>> To support nested translation, the nest parent domain is allocated with
>> IOMMU_HWPT_ALLOC_NEST_PARENT flag, and stores information of the v1 page
>> table for stage 2 (i.e. GPA->SPA).
>>
>> Also, only support nest parent domain on AMD system, which can support
>> the Guest CR3 Table (GCR3TRPMode) feature. This feature is required in
>> order to program DTE[GCR3 Table Root Pointer] with the GPA.
>>
>> Signed-off-by: Suravee Suthikulpanit<suravee.suthikulpanit@amd.com>
>> +static inline bool is_nest_parent_supported(u32 flags)
>> +{
>> +	/* Only allow nest parent when these features are supported */
>> +	if ((flags & IOMMU_HWPT_ALLOC_NEST_PARENT) &&
>> +	    (!check_feature(FEATURE_GT) ||
>> +	     !check_feature(FEATURE_GIOSUP) ||
>> +	     !check_feature2(FEATURE_GCR3TRPMODE)))
>> +		return false;
>> +
>> +	return true;
> If the "flags" doesn't have IOMMU_HWPT_ALLOC_NEST_PARENT while one
> of the features is missing, this would return true, indicating the
> HW supports nesting parent, which will be logically wrong although
> it does validate the nest parent flag.
> 
> Following the existing coding style, I think this could be just:
> 
> static inline bool is_nest_parent_supported(void)
> {
> 	/* Only allow nest parent when these features are supported */
> 	return check_feature(FEATURE_GT) && check_feature(FEATURE_GIOSUP) &&
> 	       check_feature2(FEATURE_GCR3TRPMODE);
> }

Ahh, I missed this part.

Thanks,
Suravee