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From:   "Liu, Yi L" <yi.l.liu@intel.com>
To:     Jean-Philippe Brucker <jean-philippe@linaro.org>
CC:     "Tian, Kevin" <kevin.tian@intel.com>,
        "alex.williamson@redhat.com" <alex.williamson@redhat.com>,
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        "Raj, Ashok" <ashok.raj@intel.com>,
        "Tian, Jun J" <jun.j.tian@intel.com>,
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        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "Wu, Hao" <hao.wu@intel.com>
Subject: RE: [PATCH v1 6/8] vfio/type1: Bind guest page tables to host
Thread-Topic: [PATCH v1 6/8] vfio/type1: Bind guest page tables to host
Thread-Index: AQHWAEUdkW8K+/kg/06c7098DvJyv6hgm8wAgANYlCCAAK00AIAA6IawgAEUvACABu4SMA==
Date:   Tue, 7 Apr 2020 10:33:25 +0000
Message-ID: <A2975661238FB949B60364EF0F2C25743A224C8F@SHSMSX104.ccr.corp.intel.com>
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Hi Jean,

> From: Jean-Philippe Brucker < jean-philippe@linaro.org >
> Sent: Friday, April 3, 2020 4:35 PM
> Subject: Re: [PATCH v1 6/8] vfio/type1: Bind guest page tables to host
> 
> On Thu, Apr 02, 2020 at 08:05:29AM +0000, Liu, Yi L wrote:
> > > > > > static long vfio_iommu_type1_ioctl(void *iommu_data,
> > > > > >  		default:
> > > > > >  			return -EINVAL;
> > > > > >  		}
> > > > > > +
> > > > > > +	} else if (cmd == VFIO_IOMMU_BIND) {
> > > > >
> > > > > BIND what? VFIO_IOMMU_BIND_PASID sounds clearer to me.
> > > >
> > > > Emm, it's up to the flags to indicate bind what. It was proposed to
> > > > cover the three cases below:
> > > > a) BIND/UNBIND_GPASID
> > > > b) BIND/UNBIND_GPASID_TABLE
> > > > c) BIND/UNBIND_PROCESS
> > > > <only a) is covered in this patch>
> > > > So it's called VFIO_IOMMU_BIND.
> > >
> > > but aren't they all about PASID related binding?
> >
> > yeah, I can rename it. :-)
> 
> I don't know if anyone intends to implement it, but SMMUv2 supports
> nesting translation without any PASID support. For that case the name
> VFIO_IOMMU_BIND_GUEST_PGTBL without "PASID" anywhere makes more sense.
> Ideally we'd also use a neutral name for the IOMMU API instead of
> bind_gpasid(), but that's easier to change later.

I agree VFIO_IOMMU_BIND is somehow not straight-forward. Especially, it may
cause confusion when thinking about VFIO_SET_IOMMU. How about using
VFIO_NESTING_IOMMU_BIND_STAGE1 to cover a) and b)? And has another
VFIO_BIND_PROCESS in future for the SVA bind case.

Regards,
Yi Liu