linux-kernel - RE: [PATCH RFCv1 07/14] iommufd: Add viommu set/unset_dev

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Message-ID: <BN9PR11MB5276EEC2A1DDA9C92F96737C8CF42@BN9PR11MB5276.namprd11.prod.outlook.com>
Date: Thu, 23 May 2024 06:19:59 +0000
From: "Tian, Kevin" <kevin.tian@...el.com>
To: Jason Gunthorpe <jgg@...dia.com>, Nicolin Chen <nicolinc@...dia.com>
CC: "will@...nel.org" <will@...nel.org>, "robin.murphy@....com"
	<robin.murphy@....com>, "suravee.suthikulpanit@....com"
	<suravee.suthikulpanit@....com>, "joro@...tes.org" <joro@...tes.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
	"linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>, "linux-tegra@...r.kernel.org"
	<linux-tegra@...r.kernel.org>, "Liu, Yi L" <yi.l.liu@...el.com>,
	"eric.auger@...hat.com" <eric.auger@...hat.com>, "vasant.hegde@....com"
	<vasant.hegde@....com>, "jon.grimm@....com" <jon.grimm@....com>,
	"santosh.shukla@....com" <santosh.shukla@....com>, "Dhaval.Giani@....com"
	<Dhaval.Giani@....com>, "shameerali.kolothum.thodi@...wei.com"
	<shameerali.kolothum.thodi@...wei.com>
Subject: RE: [PATCH RFCv1 07/14] iommufd: Add viommu set/unset_dev_id ops

> From: Jason Gunthorpe <jgg@...dia.com>
> Sent: Wednesday, May 22, 2024 2:25 AM
> 
> On Tue, May 14, 2024 at 06:59:07PM -0700, Nicolin Chen wrote:
> > So, you want a proxy S1 domain for a device to attach, in case
> > of a stage-2 only setup, because an S2 domain will no longer has
> > a VMID, since it's shared among viommus. In the SMMU driver case,
> > an arm_smmu_domain won't have an smmu pointer, so a device can't
> > attach to an S2 domain but always an nested S1 domain, right?
> 
> That seems like a simple solution to the VMID lifetime, but it means
> the kernel has to decode more types of vSTE.
> 

why does ATC invalidation need to know about VMID?

Or is above talking about beyond the discussion between DEV_INVALIDATE
vs. VIOMMU_INVALIDATE?