From: "Liu, Yi L" <yi.l.liu@intel.com>
To: David Gibson <david@gibson.dropbear.id.au>
Cc: "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>,
"mst@redhat.com" <mst@redhat.com>,
"pbonzini@redhat.com" <pbonzini@redhat.com>,
"alex.williamson@redhat.com" <alex.williamson@redhat.com>,
"peterx@redhat.com" <peterx@redhat.com>,
"eric.auger@redhat.com" <eric.auger@redhat.com>,
"Tian, Kevin" <kevin.tian@intel.com>,
"Tian, Jun J" <jun.j.tian@intel.com>,
"Sun, Yi Y" <yi.y.sun@intel.com>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
Jacob Pan <jacob.jun.pan@linux.intel.com>,
Yi Sun <yi.y.sun@linux.intel.com>
Subject: RE: [RFC v1 05/18] vfio/pci: add pasid alloc/free implementation
Date: Wed, 24 Jul 2019 04:57:06 +0000 [thread overview]
Message-ID: <A2975661238FB949B60364EF0F2C25743A0160C9@SHSMSX104.ccr.corp.intel.com> (raw)
In-Reply-To: <20190723035741.GR25073@umbus.fritz.box>
> From: kvm-owner@vger.kernel.org [mailto:kvm-owner@vger.kernel.org] On Behalf
> Of David Gibson
> Sent: Tuesday, July 23, 2019 11:58 AM
> To: Liu, Yi L <yi.l.liu@intel.com>
> Subject: Re: [RFC v1 05/18] vfio/pci: add pasid alloc/free implementation
>
> On Mon, Jul 22, 2019 at 07:02:51AM +0000, Liu, Yi L wrote:
> > > From: kvm-owner@vger.kernel.org [mailto:kvm-owner@vger.kernel.org]
> > > On Behalf Of David Gibson
> > > Sent: Wednesday, July 17, 2019 11:07 AM
> > > To: Liu, Yi L <yi.l.liu@intel.com>
> > > Subject: Re: [RFC v1 05/18] vfio/pci: add pasid alloc/free
> > > implementation
> > >
> > > On Tue, Jul 16, 2019 at 10:25:55AM +0000, Liu, Yi L wrote:
> > > > > From: kvm-owner@vger.kernel.org
> > > > > [mailto:kvm-owner@vger.kernel.org] On
> > > Behalf
> > > > > Of David Gibson
> > > > > Sent: Monday, July 15, 2019 10:55 AM
> > > > > To: Liu, Yi L <yi.l.liu@intel.com>
> > > > > Subject: Re: [RFC v1 05/18] vfio/pci: add pasid alloc/free
> > > > > implementation
> > > > >
> > > > > On Fri, Jul 05, 2019 at 07:01:38PM +0800, Liu Yi L wrote:
> > > > > > This patch adds vfio implementation PCIPASIDOps.alloc_pasid/free_pasid().
> > > > > > These two functions are used to propagate guest pasid
> > > > > > allocation and free requests to host via vfio container ioctl.
> > > > >
> > > > > As I said in an earlier comment, I think doing this on the
> > > > > device is conceptually incorrect. I think we need an explcit
> > > > > notion of an SVM context (i.e. the namespace in which all the
> > > > > PASIDs live) - which will IIUC usually be shared amongst
> > > > > multiple devices. The create and free PASID requests should be on that object.
> > > >
> > > > Actually, the allocation is not doing on this device. System wide,
> > > > it is done on a container. So not sure if it is the API interface
> > > > gives you a sense that this is done on device.
> > >
> > > Sorry, I should have been clearer. I can see that at the VFIO level
> > > it is done on the container. However the function here takes a bus
> > > and devfn, so this qemu internal interface is per-device, which
> > > doesn't really make sense.
> >
> > Got it. The reason here is to pass the bus and devfn info, so that
> > VFIO can figure out a container for the operation. So far in QEMU,
> > there is no good way to connect the vIOMMU emulator and VFIO regards
> > to SVM.
>
> Right, and I think that's an indication that we're not modelling something in qemu
> that we should be.
>
> > hw/pci layer is a choice based on some previous discussion. But yes, I
> > agree with you that we may need to have an explicit notion for SVM. Do
> > you think it is good to introduce a new abstract layer for SVM (may
> > name as SVMContext).
>
> I think so, yes.
>
> If nothing else, I expect we'll need this concept if we ever want to be able to
> implement SVM for emulated devices (which could be useful for debugging, even if
> it's not something you'd do in production).
>
> > The idea would be that vIOMMU maintain the SVMContext instances and
> > expose explicit interface for VFIO to get it. Then VFIO register
> > notifiers on to the SVMContext. When vIOMMU emulator wants to do PASID
> > alloc/free, it fires the corresponding notifier. After call into VFIO,
> > the notifier function itself figure out the container it is bound. In
> > this way, it's the duty of vIOMMU emulator to figure out a proper
> > notifier to fire. From interface point of view, it is no longer
> > per-device.
>
> Exactly.
Cool, let me prepare another version with the ideas. Thanks for your
review. :-)
Regards,
Yi Liu
> > Also, it leaves the PASID management details to vIOMMU emulator as it
> > can be vendor specific. Does it make sense?
> > Also, I'd like to know if you have any other idea on it. That would
> > surely be helpful. :-)
> >
> > > > Also, curious on the SVM context
> > > > concept, do you mean it a per-VM context or a per-SVM usage context?
> > > > May you elaborate a little more. :-)
> > >
> > > Sorry, I'm struggling to find a good term for this. By "context" I
> > > mean a namespace containing a bunch of PASID address spaces, those
> > > PASIDs are then visible to some group of devices.
> >
> > I see. May be the SVMContext instance above can include multiple PASID
> > address spaces. And again, I think this relationship should be
> > maintained in vIOMMU emulator.
next prev parent reply other threads:[~2019-07-24 4:57 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-05 11:01 [RFC v1 00/18] intel_iommu: expose Shared Virtual Addressing to VM Liu Yi L
2019-07-05 11:01 ` [RFC v1 01/18] linux-headers: import iommu.h from kernel Liu Yi L
2019-07-05 11:01 ` [RFC v1 02/18] linux-headers: import vfio.h " Liu Yi L
2019-07-09 1:58 ` Peter Xu
2019-07-09 8:37 ` Auger Eric
2019-07-10 12:31 ` Liu, Yi L
2019-07-10 12:29 ` Liu, Yi L
2019-07-05 11:01 ` [RFC v1 03/18] hw/pci: introduce PCIPASIDOps to PCIDevice Liu Yi L
2019-07-09 2:12 ` Peter Xu
2019-07-09 10:41 ` Auger Eric
2019-07-10 11:08 ` Liu, Yi L
2019-07-11 3:51 ` david
2019-07-11 7:13 ` Liu, Yi L
2019-07-05 11:01 ` [RFC v1 04/18] intel_iommu: add "sm_model" option Liu Yi L
2019-07-09 2:15 ` Peter Xu
2019-07-10 12:14 ` Liu, Yi L
2019-07-11 1:03 ` Peter Xu
2019-07-11 6:25 ` Liu, Yi L
2019-07-05 11:01 ` [RFC v1 05/18] vfio/pci: add pasid alloc/free implementation Liu Yi L
2019-07-09 2:23 ` Peter Xu
2019-07-10 12:16 ` Liu, Yi L
2019-07-15 2:55 ` David Gibson
2019-07-16 10:25 ` Liu, Yi L
2019-07-17 3:06 ` David Gibson
2019-07-22 7:02 ` Liu, Yi L
2019-07-23 3:57 ` David Gibson
2019-07-24 4:57 ` Liu, Yi L [this message]
2019-07-24 9:33 ` Auger Eric
2019-07-25 3:40 ` David Gibson
2019-07-26 5:18 ` Liu, Yi L
2019-08-02 7:36 ` Auger Eric
2019-07-05 11:01 ` [RFC v1 06/18] intel_iommu: support virtual command emulation and pasid request Liu Yi L
2019-07-09 3:19 ` Peter Xu
2019-07-10 11:51 ` Liu, Yi L
2019-07-11 1:13 ` Peter Xu
2019-07-11 6:59 ` Liu, Yi L
2019-07-05 11:01 ` [RFC v1 07/18] hw/pci: add pci_device_bind/unbind_gpasid Liu Yi L
2019-07-09 8:37 ` Auger Eric
2019-07-10 12:18 ` Liu, Yi L
2019-07-05 11:01 ` [RFC v1 08/18] vfio/pci: add vfio bind/unbind_gpasid implementation Liu Yi L
2019-07-09 8:37 ` Auger Eric
2019-07-10 12:30 ` Liu, Yi L
2019-07-05 11:01 ` [RFC v1 09/18] intel_iommu: process pasid cache invalidation Liu Yi L
2019-07-09 4:47 ` Peter Xu
2019-07-11 6:22 ` Liu, Yi L
2019-07-05 11:01 ` [RFC v1 10/18] intel_iommu: tag VTDAddressSpace instance with PASID Liu Yi L
2019-07-09 6:12 ` Peter Xu
2019-07-11 7:24 ` Liu, Yi L
2019-07-05 11:01 ` [RFC v1 11/18] intel_iommu: create VTDAddressSpace per BDF+PASID Liu Yi L
2019-07-09 6:39 ` Peter Xu
2019-07-11 8:13 ` Liu, Yi L
2019-07-05 11:01 ` [RFC v1 12/18] intel_iommu: bind/unbind guest page table to host Liu Yi L
2019-07-05 11:01 ` [RFC v1 13/18] intel_iommu: flush pasid cache after a DSI context cache flush Liu Yi L
2019-07-05 11:01 ` [RFC v1 14/18] hw/pci: add flush_pasid_iotlb() in PCIPASIDOps Liu Yi L
2019-07-05 11:01 ` [RFC v1 15/18] vfio/pci: adds support for PASID-based iotlb flush Liu Yi L
2019-07-05 11:01 ` [RFC v1 16/18] intel_iommu: add PASID-based iotlb invalidation support Liu Yi L
2019-07-05 11:01 ` [RFC v1 17/18] intel_iommu: propagate PASID-based iotlb flush to host Liu Yi L
2019-07-05 11:01 ` [RFC v1 18/18] intel_iommu: do not passdown pasid bind for PASID #0 Liu Yi L
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