linux-kernel - Re: [PATCH 1/1] iommu/vt-d: Fix missed device TLB cache tag

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Date: Thu, 20 Jun 2024 16:19:46 +0530
From: Vasant Hegde <vasant.hegde@....com>
To: Baolu Lu <baolu.lu@...ux.intel.com>, "Tian, Kevin"
 <kevin.tian@...el.com>, Jason Gunthorpe <jgg@...pe.ca>
Cc: Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
 Robin Murphy <robin.murphy@....com>,
 Jacek Lawrynowicz <jacek.lawrynowicz@...ux.intel.com>,
 "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/1] iommu/vt-d: Fix missed device TLB cache tag

Hi,


On 6/20/2024 11:57 AM, Baolu Lu wrote:
> On 2024/6/20 13:54, Vasant Hegde wrote:
>> On 6/20/2024 8:43 AM, Baolu Lu wrote:
>>> On 6/20/24 11:04 AM, Tian, Kevin wrote:
>>>>> From: Baolu Lu<baolu.lu@...ux.intel.com>
>>>>> Sent: Thursday, June 20, 2024 8:50 AM
>>>>>


.../...

>>>>
>>>> seems that for all domain attaches above is coded in a wrong order
>>>> as ats is enabled after the cache tag is assigned.
>>> Yes, exactly. But simply changing the order isn't future-proof,
>>> considering ATS control will eventually be moved out of iommu drivers.
>> [Unrelated to this patch]
>>
>> You mean ATS setup will be moved to individual device driver? Is there any
>> reason for that?
> 
> Not exactly to individual device drivers, but it should be out of the
> iommu drivers.
> 
> https://lore.kernel.org/linux-iommu/BL1PR12MB51441FC4303BD0442EDB7A9CF7FFA@BL1PR12MB5144.namprd12.prod.outlook.com/

Got it. Thanks.

I remember of this discussion. May be we can provide API from IOMMU driver so
that individual driver can enable/disable ATS (like iommu_dev_enable_feature()).

-Vasant