linux-kernel - RE: [PATCH v2 0/5] iommu: Enable user space IOPFs in non-PASID and non-svm cases

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Message-ID: <BN9PR11MB52761B4848ACE15A7A2384458C6C2@BN9PR11MB5276.namprd11.prod.outlook.com>
Date: Fri, 20 Sep 2024 06:57:04 +0000
From: "Tian, Kevin" <kevin.tian@...el.com>
To: Joel Granados <j.granados@...sung.com>
CC: David Woodhouse <dwmw2@...radead.org>, Lu Baolu
	<baolu.lu@...ux.intel.com>, Joerg Roedel <joro@...tes.org>, Will Deacon
	<will@...nel.org>, Robin Murphy <robin.murphy@....com>, Jason Gunthorpe
	<jgg@...pe.ca>, Klaus Jensen <its@...elevant.dk>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"iommu@...ts.linux.dev" <iommu@...ts.linux.dev>, Klaus Jensen
	<k.jensen@...sung.com>
Subject: RE: [PATCH v2 0/5] iommu: Enable user space IOPFs in non-PASID and
 non-svm cases

> From: Joel Granados <j.granados@...sung.com>
> Sent: Monday, September 16, 2024 4:51 PM
> 
> On Sat, Sep 14, 2024 at 12:48:31AM +0000, Tian, Kevin wrote:
> > > From: Joel Granados via B4 Relay
> > > <devnull+j.granados.samsung.com@...nel.org>
> > >
> > > This series makes use of iommufd_hwpt_replace_device to execute
> > > non-pasid/non-svm user space IOPFs. Our main motivation is to enable
> > > user-space driver driven device verification without SVM/PASID.
> >
> > can you elaborate why IOPFs are necessary to help verify such usage?
> 
> In retrospect "enable" might not be the best word to use here. We are not
> "enabling" user-space driver driven device verification as it is already
> enabled; you could already poke a device from user space. But the whole
> poke
> space was not available, you could not test IOPF without having an
> SVM/PASID
> capable IOMMU. Therefore a better wording would be "Our main motivation
> is to
> expand or facilitate user-space driver driven device verification by enabling
> IOPF without SMV/PASID".
> 

hmm did you actually see a IOMMU which supports IOPF only but
not SVM/PASID? 

this series alone has its merit, e.g. postcopy migration might want
such notification. But not sure it helps solve a real problem in your side...