linux-kernel - RE: [PATCH v4 5/5] vfio: Support IO page table replacement

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Message-ID: <BN9PR11MB52763E69446196B5D4C109E28CB99@BN9PR11MB5276.namprd11.prod.outlook.com>
Date:   Mon, 13 Mar 2023 02:04:04 +0000
From:   "Tian, Kevin" <kevin.tian@...el.com>
To:     Nicolin Chen <nicolinc@...dia.com>
CC:     "jgg@...dia.com" <jgg@...dia.com>,
        "joro@...tes.org" <joro@...tes.org>,
        "will@...nel.org" <will@...nel.org>,
        "robin.murphy@....com" <robin.murphy@....com>,
        "alex.williamson@...hat.com" <alex.williamson@...hat.com>,
        "shuah@...nel.org" <shuah@...nel.org>,
        "Liu, Yi L" <yi.l.liu@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kselftest@...r.kernel.org" <linux-kselftest@...r.kernel.org>,
        "mjrosato@...ux.ibm.com" <mjrosato@...ux.ibm.com>,
        "farman@...ux.ibm.com" <farman@...ux.ibm.com>
Subject: RE: [PATCH v4 5/5] vfio: Support IO page table replacement

> From: Nicolin Chen <nicolinc@...dia.com>
> Sent: Saturday, March 11, 2023 7:38 AM
> 
> On Fri, Mar 10, 2023 at 11:53:56AM +0000, Tian, Kevin wrote:
> > External email: Use caution opening links or attachments
> >
> >
> > > From: Nicolin Chen <nicolinc@...dia.com>
> > > Sent: Wednesday, March 8, 2023 10:26 PM
> > >
> > > Now both the physical path and the emulated path should support an IO
> > > page
> > > table replacement.
> > >
> > > Call iommufd_device_replace() when vdev->iommufd_attached is true.
> > >
> >
> > why is replace enabled only in physical path in this patch?
> 
> The emulated pathway does not call iommufd_device_attach() but
> iommufd_access_set_ioas() in the other patch, which internally
> takes care of the replacement for the access pointer.
> 

I thought there is a similar check as in physical path which should
be removed:

	if (vdev->iommufd_attached)
-		return -EBUSY;

but looks it's not the case for the emulated path.