Re: [PATCH v5 15/19] iommufd: vfio container FD ioctl compatibility

From: Jason Wang <jasowang@redhat.com>
To: "Tian, Kevin" <kevin.tian@intel.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>,
	"bpf@vger.kernel.org" <bpf@vger.kernel.org>,
	 Jonathan Corbet <corbet@lwn.net>,
	David Woodhouse <dwmw2@infradead.org>,
	 "iommu@lists.linux.dev" <iommu@lists.linux.dev>,
	Joerg Roedel <joro@8bytes.org>,
	 "linux-doc@vger.kernel.org" <linux-doc@vger.kernel.org>,
	 "linux-kselftest@vger.kernel.org"
	<linux-kselftest@vger.kernel.org>,
	 "llvm@lists.linux.dev" <llvm@lists.linux.dev>,
	Nathan Chancellor <nathan@kernel.org>,
	 Nick Desaulniers <ndesaulniers@google.com>,
	Miguel Ojeda <ojeda@kernel.org>,
	 Robin Murphy <robin.murphy@arm.com>,
	Shuah Khan <shuah@kernel.org>,
	 Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>,
	Tom Rix <trix@redhat.com>,  Will Deacon <will@kernel.org>,
	Anthony Krowiak <akrowiak@linux.ibm.com>,
	 Alex Williamson <alex.williamson@redhat.com>,
	Bagas Sanjaya <bagasdotme@gmail.com>,
	 Lu Baolu <baolu.lu@linux.intel.com>,
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	"Yang, Lixiao" <lixiao.yang@intel.com>,
	 Matthew Rosato <mjrosato@linux.ibm.com>,
	"Michael S. Tsirkin" <mst@redhat.com>,
	 Nicolin Chen <nicolinc@nvidia.com>,
	Halil Pasic <pasic@linux.ibm.com>,
	 Niklas Schnelle <schnelle@linux.ibm.com>,
	 Shameerali Kolothum Thodi <shameerali.kolothum.thodi@huawei.com>,
	"Liu, Yi L" <yi.l.liu@intel.com>,
	 Keqian Zhu <zhukeqian1@huawei.com>
Subject: Re: [PATCH v5 15/19] iommufd: vfio container FD ioctl compatibility
Date: Wed, 23 Nov 2022 12:31:15 +0800	[thread overview]
Message-ID: <CACGkMEumUoHfWE0NkdmNbnx-nmgXrm3ZL6Jrj6x+M=wSXQK32g@mail.gmail.com> (raw)
In-Reply-To: <BN9PR11MB5276939555C1460EFBFD15A68C0C9@BN9PR11MB5276.namprd11.prod.outlook.com>

On Wed, Nov 23, 2022 at 9:33 AM Tian, Kevin <kevin.tian@intel.com> wrote:
>
> > From: Jason Gunthorpe <jgg@nvidia.com>
> > Sent: Friday, November 18, 2022 11:22 PM
> >
> > On Fri, Nov 18, 2022 at 02:58:49AM +0000, Tian, Kevin wrote:
> > > > From: Jason Gunthorpe <jgg@nvidia.com>
> > > > Sent: Thursday, November 17, 2022 5:01 AM
> > > > index ca28a135b9675f..2fdff04000b326 100644
> > > > --- a/drivers/iommu/iommufd/Makefile
> > > > +++ b/drivers/iommu/iommufd/Makefile
> > > > @@ -5,6 +5,7 @@ iommufd-y := \
> > > >   io_pagetable.o \
> > > >   ioas.o \
> > > >   main.o \
> > > > - pages.o
> > > > + pages.o \
> > > > + vfio_compat.o
> > > >
> > >
> > > move vfio_compat out of core? it's not required if VFIO
> > > is not configured.
> >
> > We can, but I don't know if we should. Compat ioctls are part of
> > /dev/iommu, and technically have nothing to do with VFIO. A native
> > iommufd application using VDPA could use them, if it wanted, for
> > instance.
> >
>
> I'm not sure whether that requires further VDPA support. Be safe
> I'd like VDPA to explicitly select vfio_compact when that new
> mixed scheme is supported.
>

This sounds strange. If I don't misunderstand the code, it tries to
provide ioctl compatibility with the VFIO container. I don't see how
it can be used for vDPA, the ioctls used by vDPA is not compatible
with VFIO.

Thanks