linux-kernel - RE: [PATCH v3 13/14] vfio: Document dual stage control

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Message-ID: <CY4PR11MB14322E99A64BC0B2E06CD33CC36E0@CY4PR11MB1432.namprd11.prod.outlook.com>
Date:   Mon, 29 Jun 2020 09:24:50 +0000
From:   "Liu, Yi L" <yi.l.liu@...el.com>
To:     Stefan Hajnoczi <stefanha@...il.com>
CC:     "alex.williamson@...hat.com" <alex.williamson@...hat.com>,
        "eric.auger@...hat.com" <eric.auger@...hat.com>,
        "baolu.lu@...ux.intel.com" <baolu.lu@...ux.intel.com>,
        "joro@...tes.org" <joro@...tes.org>,
        "Tian, Kevin" <kevin.tian@...el.com>,
        "jacob.jun.pan@...ux.intel.com" <jacob.jun.pan@...ux.intel.com>,
        "Raj, Ashok" <ashok.raj@...el.com>,
        "Tian, Jun J" <jun.j.tian@...el.com>,
        "Sun, Yi Y" <yi.y.sun@...el.com>,
        "jean-philippe@...aro.org" <jean-philippe@...aro.org>,
        "peterx@...hat.com" <peterx@...hat.com>,
        "Wu, Hao" <hao.wu@...el.com>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v3 13/14] vfio: Document dual stage control

> From: Stefan Hajnoczi <stefanha@...il.com>
> Sent: Monday, June 29, 2020 5:22 PM
> 
> On Wed, Jun 24, 2020 at 01:55:26AM -0700, Liu Yi L wrote:
> > +Details can be found in Documentation/userspace-api/iommu.rst. For
> > +Intel VT-d, each stage 1 page table is bound to host by:
> > +
> > +    nesting_op->flags = VFIO_IOMMU_NESTING_OP_BIND_PGTBL;
> > +    memcpy(&nesting_op->data, &bind_data, sizeof(bind_data));
> > +    ioctl(container->fd, VFIO_IOMMU_NESTING_OP, nesting_op);
> > +
> > +As mentioned above, guest OS may use stage 1 for GIOVA->GPA or GVA->GPA.
> > +GVA->GPA page tables are available when PASID (Process Address Space
> > +GVA->ID)
> > +is exposed to guest. e.g. guest with PASID-capable devices assigned.
> > +For such page table binding, the bind_data should include PASID info,
> > +which is allocated by guest itself or by host. This depends on
> > +hardware vendor e.g. Intel VT-d requires to allocate PASID from host.
> > +This requirement is defined by the Virtual Command Support in VT-d
> > +3.0 spec, guest software running on VT-d should allocate PASID from
> > +host kernel. To allocate PASID from host, user space should +check
> > +the IOMMU_NESTING_FEAT_SYSWIDE_PASID
> 
> s/+check/check/g

got it.

> Reviewed-by: Stefan Hajnoczi <stefanha@...hat.com>

thanks :-)

Regards,
Yi Liu