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

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Message-ID: <ZvxDOfPEbot1HUkU@Asurada-Nvidia>
Date: Tue, 1 Oct 2024 11:45:13 -0700
From: Nicolin Chen <nicolinc@...dia.com>
To: Jason Gunthorpe <jgg@...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 10:46:20AM -0300, Jason Gunthorpe wrote:
> 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

Oh, I think I already have that then:
ictx->xarray: objIds <-> { IOAS|HWPT|VIOMMU|VDEVICE|.. }->objs
viommu->xarray: vRids <-> { VDEVICE } pointers

Thanks
Nicolin