linux-kernel - Re: [PATCH v2 06/19] iommufd/viommu: Add IOMMU_VIOMMU_SET/UNSET_VDEV

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Message-ID: <20241001134620.GF1365916@nvidia.com>
Date: Tue, 1 Oct 2024 10:46:20 -0300
From: Jason Gunthorpe <jgg@...dia.com>
To: Nicolin Chen <nicolinc@...dia.com>
Cc: Dan Williams <dan.j.williams@...el.com>, kevin.tian@...el.com,
	will@...nel.org, joro@...tes.org, suravee.suthikulpanit@....com,
	robin.murphy@....com, dwmw2@...radead.org, baolu.lu@...ux.intel.com,
	shuah@...nel.org, linux-kernel@...r.kernel.org,
	iommu@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org,
	linux-kselftest@...r.kernel.org, eric.auger@...hat.com,
	jean-philippe@...aro.org, mdf@...nel.org, mshavit@...gle.com,
	shameerali.kolothum.thodi@...wei.com, smostafa@...gle.com,
	yi.l.liu@...el.com
Subject: Re: [PATCH v2 06/19] iommufd/viommu: Add
 IOMMU_VIOMMU_SET/UNSET_VDEV_ID ioctl

On Tue, Oct 01, 2024 at 01:54:05AM -0700, Nicolin Chen wrote:
> On Thu, Sep 05, 2024 at 10:38:23AM -0700, Nicolin Chen wrote:
> > On Thu, Sep 05, 2024 at 01:03:53PM -0300, Jason Gunthorpe wrote:
> > > On Tue, Aug 27, 2024 at 09:59:43AM -0700, Nicolin Chen wrote:
> > > > Introduce a pair of new ioctls to set/unset a per-viommu virtual device id
> > > > that should be linked to a physical device id via an idev pointer.
> > > 
> > > Given some of the other discussions around CC I suspect we should
> > > rename these to 'create/destroy virtual device' with an eye that
> > > eventually they would be extended like other ops with per-CC platform
> > > data.
> > > 
> > > ie this would be the interface to tell the CC trusted world that a
> > > secure device is being added to a VM with some additional flags..
> > > 
> > > Right now it only conveys the vRID parameter of the virtual device
> > > being created.
> > >
> > > A following question is if these objects should have their own IDs in
> > > the iommufd space too, and then unset is not unset but just a normal
> > > destroy object. If so then the thing you put in the ids xarray would
> > > also just be a normal object struct.
> 
> I found that adding it as a new object makes things a lot of easier
> since a vdevice can take refcounts of both viommu and idev. So both
> destroy() callbacks wouldn't be bothered.
> 
> While confirming if I am missing something from the review comments,
> I am not quite sure what is "the thing you put in the ids xarray"..
> I only added a vRID xarray per viommu, yet that doesn't seem to be
> able to merge into the normal object struct. Mind elaborating?

I would think to point the vRID xarray directly to the new iommufd
vdevice object

Jason