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From: "Raj, Ashok" <ashok.raj@intel.com>
To: Jacob Pan <jacob.jun.pan@linux.intel.com>
Cc: kevin.tian@intel.com, Ashok Raj <ashok.raj@intel.com>,
	kvm@vger.kernel.org, sanjay.k.kumar@intel.com,
	yi.y.sun@intel.com, iommu@lists.linux-foundation.org,
	linux-kernel@vger.kernel.org,
	Alex Williamson <alex.williamson@redhat.com>,
	David Woodhouse <dwmw2@infradead.org>
Subject: Re: [RFC PATCH 0/4] Use 1st-level for DMA remapping in guest
Date: Mon, 23 Sep 2019 13:25:52 -0700
Message-ID: <20190923202552.GA21816@araj-mobl1.jf.intel.com> (raw)
In-Reply-To: <20190923122715.53de79d0@jacob-builder>

Hi Jacob

On Mon, Sep 23, 2019 at 12:27:15PM -0700, Jacob Pan wrote:
> > 
> > In VT-d 3.0, scalable mode is introduced, which offers two level
> > translation page tables and nested translation mode. Regards to
> > GIOVA support, it can be simplified by 1) moving the GIOVA support
> > over 1st-level page table to store GIOVA->GPA mapping in vIOMMU,
> > 2) binding vIOMMU 1st level page table to the pIOMMU, 3) using pIOMMU
> > second level for GPA->HPA translation, and 4) enable nested (a.k.a.
> > dual stage) translation in host. Compared with current shadow GIOVA
> > support, the new approach is more secure and software is simplified
> > as we only need to flush the pIOMMU IOTLB and possible device-IOTLB
> > when an IOVA mapping in vIOMMU is torn down.
> > 
> >      .-----------.
> >      |  vIOMMU   |
> >      |-----------|                 .-----------.
> >      |           |IOTLB flush trap |   QEMU    |
> >      .-----------.    (unmap)      |-----------|
> >      | GVA->GPA  |---------------->|           |
> >      '-----------'                 '-----------'
> >      |           |                       |
> >      '-----------'                       |
> >            <------------------------------
> >            |      VFIO/IOMMU          
> >            |  cache invalidation and  
> >            | guest gpd bind interfaces
> >            v
> For vSVA, the guest PGD bind interface will mark the PASID as guest
> PASID and will inject page request into the guest. In FL gIOVA case, I
> guess we are assuming there is no page fault for GIOVA. I will need to
> add a flag in the gpgd bind such that any PRS will be auto responded
> with invalid.

Is there real need to enforce this? I'm not sure if there is any
limitation in the spec, and if so, can the guest check that instead?

Also i believe the idea is to overcommit PASID#0 such uses. Thought
we had a capability to expose this to the vIOMMU as well. Not sure if this
is already documented, if not should be up in the next rev.


> 
> Also, native use of IOVA FL map is not to be supported? i.e. IOMMU API
> and DMA API for native usage will continue to be SL only?
> >      .-----------.
> >      |  pIOMMU   |
> >      |-----------|
> >      .-----------.
> >      | GVA->GPA  |<---First level
> >      '-----------'
> >      | GPA->HPA  |<---Scond level

s/Scond/Second

> >      '-----------'
> >      '-----------'
> > 
> > This patch series only aims to achieve the first goal, a.k.a using
> > first level translation for IOVA mappings in vIOMMU. I am sending
> > it out for your comments. Any comments, suggestions and concerns are
> > welcomed.
> > 
> 
> 
> > Based-on-idea-by: Ashok Raj <ashok.raj@intel.com>
> > Based-on-idea-by: Kevin Tian <kevin.tian@intel.com>
> > Based-on-idea-by: Liu Yi L <yi.l.liu@intel.com>
> > Based-on-idea-by: Lu Baolu <baolu.lu@linux.intel.com>
> > Based-on-idea-by: Sanjay Kumar <sanjay.k.kumar@intel.com>
> > 
> > Lu Baolu (4):
> >   iommu/vt-d: Move domain_flush_cache helper into header
> >   iommu/vt-d: Add first level page table interfaces
> >   iommu/vt-d: Map/unmap domain with mmmap/mmunmap
> >   iommu/vt-d: Identify domains using first level page table
> > 
> >  drivers/iommu/Makefile             |   2 +-
> >  drivers/iommu/intel-iommu.c        | 142 ++++++++++--
> >  drivers/iommu/intel-pgtable.c      | 342
> > +++++++++++++++++++++++++++++ include/linux/intel-iommu.h        |
> > 31 ++- include/trace/events/intel_iommu.h |  60 +++++
> >  5 files changed, 553 insertions(+), 24 deletions(-)
> >  create mode 100644 drivers/iommu/intel-pgtable.c
> > 
> 
> [Jacob Pan]
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  reply index

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-23 12:24 Lu Baolu
2019-09-23 12:24 ` [RFC PATCH 1/4] iommu/vt-d: Move domain_flush_cache helper into header Lu Baolu
2019-09-23 12:24 ` [RFC PATCH 2/4] iommu/vt-d: Add first level page table interfaces Lu Baolu
2019-09-23 20:31   ` Raj, Ashok
2019-09-24  1:38     ` Lu Baolu
2019-09-25  4:30       ` Peter Xu
2019-09-25  4:38         ` Tian, Kevin
2019-09-25  5:24           ` Peter Xu
2019-09-25  6:52             ` Lu Baolu
2019-09-25  7:32               ` Tian, Kevin
2019-09-25  8:35                 ` Peter Xu
2019-09-26  1:42                 ` Lu Baolu
2019-09-25  5:21   ` Peter Xu
2019-09-26  2:35     ` Lu Baolu
2019-09-26  3:49       ` Peter Xu
2019-09-27  2:27         ` Lu Baolu
2019-09-27  5:34           ` Peter Xu
2019-09-28  8:23             ` Lu Baolu
2019-09-29  5:25               ` Peter Xu
2019-10-08  2:20                 ` Lu Baolu
2019-09-23 12:24 ` [RFC PATCH 3/4] iommu/vt-d: Map/unmap domain with mmmap/mmunmap Lu Baolu
2019-09-25  5:00   ` Tian, Kevin
2019-09-25  7:06     ` Lu Baolu
2019-09-23 12:24 ` [RFC PATCH 4/4] iommu/vt-d: Identify domains using first level page table Lu Baolu
2019-09-25  6:50   ` Peter Xu
2019-09-25  7:35     ` Tian, Kevin
2019-09-23 19:27 ` [RFC PATCH 0/4] Use 1st-level for DMA remapping in guest Jacob Pan
2019-09-23 20:25   ` Raj, Ashok [this message]
2019-09-24  4:40     ` Lu Baolu
2019-09-24  7:00     ` Tian, Kevin
2019-09-25  2:48       ` Lu Baolu
2019-09-25  6:56         ` Peter Xu
2019-09-25  7:21           ` Tian, Kevin
2019-09-25  7:45             ` Peter Xu
2019-09-25  8:02               ` Tian, Kevin
2019-09-25  8:52                 ` Peter Xu
2019-09-26  1:37                   ` Lu Baolu
2019-09-24  4:27   ` Lu Baolu

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