linux-kernel - Re: [PATCH 01/12] iommu/vt-d: Add cache tag assignment interface

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Message-ID: <4e47aff7-aa65-4c60-a5dc-b7e0f2737a3e@linux.intel.com>
Date: Thu, 11 Apr 2024 21:17:41 +0800
From: Baolu Lu <baolu.lu@...ux.intel.com>
To: "Tian, Kevin" <kevin.tian@...el.com>, Jason Gunthorpe <jgg@...pe.ca>
Cc: baolu.lu@...ux.intel.com, Joerg Roedel <joro@...tes.org>,
 Will Deacon <will@...nel.org>, Robin Murphy <robin.murphy@....com>,
 "Zhang, Tina" <tina.zhang@...el.com>, "Liu, Yi L" <yi.l.liu@...el.com>,
 "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 01/12] iommu/vt-d: Add cache tag assignment interface

On 2024/4/11 7:14, Tian, Kevin wrote:
>> From: Jason Gunthorpe <jgg@...pe.ca>
>> Sent: Wednesday, April 10, 2024 11:42 PM
>>
>> On Mon, Mar 25, 2024 at 10:16:54AM +0800, Lu Baolu wrote:
>>> +static int __cache_tag_assign_parent_domain(struct dmar_domain
>> *domain, u16 did,
>>> +					    struct device *dev, ioasid_t pasid)
>>> +{
>>> +	struct device_domain_info *info = dev_iommu_priv_get(dev);
>>> +	int ret;
>>> +
>>> +	ret = cache_tag_assign(domain, did, dev, pasid,
>> CACHE_TAG_TYPE_PARENT_IOTLB);
>>> +	if (ret || !info->ats_enabled)
>>> +		return ret;
>>
>> I'm not sure I understood the point of PARENT_IOTLB? I didn't see any
>> different implementation?
>>
>> Isn't this backwards though? Each domain should have a list of things
>> to invalidate if the domain itself changes.
>>
>> So the nesting parent should have a list of CHILD_DEVTLB's that need
>> cleaning. That list is changed when the nesting domains are attached
>> to something.
>>
> 
> probably just a naming confusion. it's called PARENT_IOTLB from the
> angle that this domain is used as a parent domain but actually it
> tracks the child tags in nested attach.

Is NESTING_IOTLB more readable?

Best regards,
baolu