linux-kernel - Re: [PATCH V4 05/18] iommu/ioasid: Redefine IOASID set and allocation APIs

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Date:   Thu, 1 Apr 2021 10:15:33 -0300
From:   Jason Gunthorpe <jgg@...dia.com>
To:     "Liu, Yi L" <yi.l.liu@...el.com>
Cc:     "Tian, Kevin" <kevin.tian@...el.com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Joerg Roedel <joro@...tes.org>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        David Woodhouse <dwmw2@...radead.org>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        "cgroups@...r.kernel.org" <cgroups@...r.kernel.org>,
        Tejun Heo <tj@...nel.org>, Li Zefan <lizefan@...wei.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Jean-Philippe Brucker <jean-philippe@...aro.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        Eric Auger <eric.auger@...hat.com>,
        Jonathan Corbet <corbet@....net>,
        "Raj, Ashok" <ashok.raj@...el.com>, "Wu, Hao" <hao.wu@...el.com>,
        "Jiang, Dave" <dave.jiang@...el.com>
Subject: Re: [PATCH V4 05/18] iommu/ioasid: Redefine IOASID set and
 allocation APIs

On Thu, Apr 01, 2021 at 01:10:48PM +0000, Liu, Yi L wrote:
> > From: Jason Gunthorpe <jgg@...dia.com>
> > Sent: Thursday, April 1, 2021 7:47 PM
> [...]
> > I'm worried Intel views the only use of PASID in a guest is with
> > ENQCMD, but that is not consistent with the industry. We need to see
> > normal nested PASID support with assigned PCI VFs.
> 
> I'm not quire flow here. Intel also allows PASID usage in guest without
> ENQCMD. e.g. Passthru a PF to guest, and use PASID on it without ENQCMD.

Then you need all the parts, the hypervisor calls from the vIOMMU, and
you can't really use a vPASID.

I'm not sure how Intel intends to resolve all of this.

> > > - this per-ioasid SVA operations is not aligned with the native SVA usage
> > >   model. Native SVA bind is per-device.
> > 
> > Seems like that is an error in native SVA.
> > 
> > SVA is a particular mode of the PASID's memory mapping table, it has
> > nothing to do with a device.
> 
> I think it still has relationship with device. This is determined by the
> DMA remapping hierarchy in hardware. e.g. Intel VT-d, the DMA isolation is
> enforced first in device granularity and then PASID granularity. SVA makes
> usage of both PASID and device granularity isolation.

When the device driver authorizes a PASID the VT-d stuff should setup
the isolation parameters for the give pci_device and PASID.

Do not leak implementation details like this as uAPI. Authorization
and memory map are distinct ideas with distinct interfaces. Do not mix
them.

Jason