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From: Jason Gunthorpe <jgg@nvidia.com>
To: Jean-Philippe Brucker <jean-philippe@linaro.org>
Cc: Jason Wang <jasowang@redhat.com>, Liu Yi L <yi.l.liu@intel.com>,
	<alex.williamson@redhat.com>, <eric.auger@redhat.com>,
	<baolu.lu@linux.intel.com>, <joro@8bytes.org>,
	<kevin.tian@intel.com>, <jacob.jun.pan@linux.intel.com>,
	<ashok.raj@intel.com>, <jun.j.tian@intel.com>,
	<yi.y.sun@intel.com>, <peterx@redhat.com>, <hao.wu@intel.com>,
	<stefanha@gmail.com>, <iommu@lists.linux-foundation.org>,
	<kvm@vger.kernel.org>, "Michael S. Tsirkin" <mst@redhat.com>
Subject: Re: [PATCH v7 00/16] vfio: expose virtual Shared Virtual Addressing to VMs
Date: Mon, 14 Sep 2020 10:47:38 -0300	[thread overview]
Message-ID: <20200914134738.GX904879@nvidia.com> (raw)
In-Reply-To: <20200914133113.GB1375106@myrica>

On Mon, Sep 14, 2020 at 03:31:13PM +0200, Jean-Philippe Brucker wrote:

> > Jason suggest something like /dev/sva. There will be a lot of other
> > subsystems that could benefit from this (e.g vDPA).
> 
> Do you have a more precise idea of the interface /dev/sva would provide,
> how it would interact with VFIO and others?  vDPA could transport the
> generic iommu.h structures via its own uAPI, and call the IOMMU API
> directly without going through an intermediate /dev/sva handle.

Prior to PASID IOMMU really only makes sense as part of vfio-pci
because the iommu can only key on the BDF. That can't work unless the
whole PCI function can be assigned. It is hard to see how a shared PCI
device can work with IOMMU like this, so may as well use vfio.

SVA and various vIOMMU models change this, a shared PCI driver can
absoultely work with a PASID that is assigned to a VM safely, and
actually don't need to know if their PASID maps a mm_struct or
something else.

So, some /dev/sva is another way to allocate a PASID that is not 1:1
with mm_struct, as the existing SVA stuff enforces. ie it is a way to
program the DMA address map of the PASID.

This new PASID allocator would match the guest memory layout and
support the IOMMU nesting stuff needed for vPASID.

This is the common code for the complex cases of virtualization with
PASID, shared by all user DMA drivers, including VFIO.

It doesn't make a lot of sense to build a uAPI exclusive to VFIO just
for PASID and vPASID. We already know everything doing user DMA will
eventually need this stuff.

Jason

  reply	other threads:[~2020-09-14 14:09 UTC|newest]

Thread overview: 81+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-10 10:45 [PATCH v7 00/16] vfio: expose virtual Shared Virtual Addressing to VMs Liu Yi L
2020-09-10 10:45 ` [PATCH v7 01/16] iommu: Report domain nesting info Liu Yi L
2020-09-11 19:38   ` Alex Williamson
2020-09-10 10:45 ` [PATCH v7 02/16] iommu/smmu: Report empty " Liu Yi L
2021-01-12  6:50   ` Vivek Gautam
2021-01-12  9:21     ` Liu, Yi L
2021-01-12 11:05       ` Vivek Gautam
2021-01-13  5:56         ` Liu, Yi L
2021-01-19 10:03           ` Auger Eric
2021-01-23  8:59             ` Liu, Yi L
2021-02-12  7:14               ` Vivek Gautam
2021-02-12  9:57                 ` Auger Eric
2021-02-12 10:18                   ` Vivek Kumar Gautam
2021-02-12 11:01                     ` Vivek Kumar Gautam
2021-03-03  9:44                   ` Liu, Yi L
2020-09-10 10:45 ` [PATCH v7 03/16] vfio/type1: Report iommu nesting info to userspace Liu Yi L
2020-09-11 20:16   ` Alex Williamson
2020-09-12  8:24     ` Liu, Yi L
2020-09-10 10:45 ` [PATCH v7 04/16] vfio: Add PASID allocation/free support Liu Yi L
2020-09-11 20:54   ` Alex Williamson
2020-09-15  4:03     ` Liu, Yi L
2020-09-10 10:45 ` [PATCH v7 05/16] iommu/vt-d: Support setting ioasid set to domain Liu Yi L
2020-09-10 10:45 ` [PATCH v7 06/16] iommu/vt-d: Remove get_task_mm() in bind_gpasid() Liu Yi L
2020-09-10 10:45 ` [PATCH v7 07/16] vfio/type1: Add VFIO_IOMMU_PASID_REQUEST (alloc/free) Liu Yi L
2020-09-11 21:38   ` Alex Williamson
2020-09-10 10:45 ` [PATCH v7 08/16] iommu: Pass domain to sva_unbind_gpasid() Liu Yi L
2020-09-10 10:45 ` [PATCH v7 09/16] iommu/vt-d: Check ownership for PASIDs from user-space Liu Yi L
2020-09-10 10:45 ` [PATCH v7 10/16] vfio/type1: Support binding guest page tables to PASID Liu Yi L
2020-09-11 22:03   ` Alex Williamson
2020-09-12  6:02     ` Liu, Yi L
2020-09-10 10:45 ` [PATCH v7 11/16] vfio/type1: Allow invalidating first-level/stage IOMMU cache Liu Yi L
2020-09-10 10:45 ` [PATCH v7 12/16] vfio/type1: Add vSVA support for IOMMU-backed mdevs Liu Yi L
2020-09-10 10:45 ` [PATCH v7 13/16] vfio/pci: Expose PCIe PASID capability to guest Liu Yi L
2020-09-11 22:13   ` Alex Williamson
2020-09-12  7:17     ` Liu, Yi L
2020-09-10 10:45 ` [PATCH v7 14/16] vfio: Document dual stage control Liu Yi L
2020-09-10 10:45 ` [PATCH v7 15/16] iommu/vt-d: Only support nesting when nesting caps are consistent across iommu units Liu Yi L
2020-09-10 10:45 ` [PATCH v7 16/16] iommu/vt-d: Support reporting nesting capability info Liu Yi L
2020-09-14  4:20 ` [PATCH v7 00/16] vfio: expose virtual Shared Virtual Addressing to VMs Jason Wang
2020-09-14  8:01   ` Tian, Kevin
2020-09-14  8:57     ` Jason Wang
2020-09-14 10:38       ` Tian, Kevin
2020-09-14 11:38         ` Jason Gunthorpe
2020-09-14 13:31   ` Jean-Philippe Brucker
2020-09-14 13:47     ` Jason Gunthorpe [this message]
2020-09-14 16:22       ` Raj, Ashok
2020-09-14 16:33         ` Jason Gunthorpe
2020-09-14 16:58           ` Alex Williamson
2020-09-14 17:41             ` Jason Gunthorpe
2020-09-14 18:23               ` Alex Williamson
2020-09-14 19:00                 ` Jason Gunthorpe
2020-09-14 22:33                   ` Alex Williamson
2020-09-15 14:29                     ` Jason Gunthorpe
2020-09-16  1:19                       ` Tian, Kevin
2020-09-16  8:32                         ` Jean-Philippe Brucker
2020-09-16 14:51                           ` Jason Gunthorpe
2020-09-16 16:20                             ` Jean-Philippe Brucker
2020-09-16 16:32                               ` Jason Gunthorpe
2020-09-16 16:50                                 ` Auger Eric
2020-09-16 14:44                         ` Jason Gunthorpe
2020-09-17  6:01                           ` Tian, Kevin
     [not found]                   ` <20200914224438.GA65940@otc-nc-03>
2020-09-15 11:33                     ` Jason Gunthorpe
2020-09-15 18:11                       ` Raj, Ashok
2020-09-15 18:45                         ` Jason Gunthorpe
2020-09-15 19:26                           ` Raj, Ashok
2020-09-15 23:45                             ` Jason Gunthorpe
2020-09-16  2:33                             ` Jason Wang
2020-09-15 22:08                           ` Jacob Pan
2020-09-15 23:51                             ` Jason Gunthorpe
     [not found]                               ` <20200915171319.00003f59@linux.intel.com>
2020-09-16  1:46                                 ` Lu Baolu
2020-09-16 15:07                                 ` Jason Gunthorpe
2020-09-16 16:33                                   ` Raj, Ashok
2020-09-16 17:01                                     ` Jason Gunthorpe
2020-09-16 18:21                                       ` Jacob Pan (Jun)
2020-09-16 18:38                                         ` Jason Gunthorpe
2020-09-16 23:09                                           ` Jacob Pan (Jun)
2020-09-17  3:53                                             ` Jason Wang
2020-09-17 17:31                                               ` Jason Gunthorpe
2020-09-17 18:17                                               ` Jacob Pan (Jun)
2020-09-18  3:58                                                 ` Jason Wang
2020-09-16  2:29     ` Jason Wang

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