RE: [PATCH v9 04/12] vfio iommu: Add support for mediated devices

From	"Tian, Kevin" <kevin.tian@intel.com>
Newsgroups	linux.kernel
Subject	RE: [PATCH v9 04/12] vfio iommu: Add support for mediated devices
Date	2016-10-26 10:00 +0200
Message-ID	<swrhT-A6-5@gated-at.bofh.it> (permalink)
References	<stnDQ-JF-5@gated-at.bofh.it> <stnDQ-JF-25@gated-at.bofh.it> <su6hA-6GV-13@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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> From: Tian, Kevin
> Sent: Wednesday, October 26, 2016 3:54 PM
> 
> > From: Alex Williamson [mailto:alex.williamson@redhat.com]
> > Sent: Thursday, October 20, 2016 5:03 AM
> > > @@ -83,6 +92,21 @@ struct vfio_group {
> > >  };
> > >
> > >  /*
> > > + * Guest RAM pinning working set or DMA target
> > > + */
> > > +struct vfio_pfn {
> > > +	struct rb_node		node;
> > > +	unsigned long		vaddr;		/* virtual addr */
> > > +	dma_addr_t		iova;		/* IOVA */
> > > +	unsigned long		pfn;		/* Host pfn */
> > > +	int			prot;
> > > +	atomic_t		ref_count;
> > > +};
> >
> > Somehow we're going to need to fit an invalidation callback here too.
> > How would we handle a case where there are multiple mdev devices, from
> > different vendor drivers, that all have the same pfn pinned?  I'm
> > already concerned about the per pfn overhead we're introducing here so
> > clearly we cannot store an invalidation callback per pinned page, per
> > vendor driver.  Perhaps invalidations should be done using a notifier
> > chain per vfio_iommu, the vendor drivers are required to register on
> > that chain (fail pinning with empty notifier list) user unmapping
> > will be broadcast to the notifier chain, the vendor driver will be
> > responsible for deciding if each unmap is relevant to them (potentially
> > it's for a pinning from another driver).
> >
> > I expect we also need to enforce that vendors perform a synchronous
> > unmap such that after returning from the notifier list call, the
> > vfio_pfn should no longer exist.  If it does we might need to BUG_ON.
> > Also be careful to pay attention to the locking of the notifier vs
> > unpin callbacks to avoid deadlocks.
> >
> 
> What about just requesting vendor driver to provide a callback in parent
> device ops?
> 
> Curious in which scenario the user application (say Qemu here) may
> unmap memory pages which are still pinned by vendor driver... Is it
> purely about a corner case which we want to handle elegantly?
> 
> If yes, possibly a simpler way is to force destroying mdev instead of
> asking vendor driver to take care of each invalidation request under
> such situation. Since anyway the mdev device won't be in an usable
> state anymore... (sorry if I missed the key problem here.)
> 

or calling reset callback of parent device driver, if we don't want to
break libvirt's expectation by blindly removing mdev device...

Thread

[PATCH v9 00/12] Add Mediated device support Kirti Wankhede <kwankhede@nvidia.com> - 2016-10-17 23:30 +0200
  [PATCH v9 10/12] vfio: Add function to get device_api string from vfio_device_info.flags Kirti Wankhede <kwankhede@nvidia.com> - 2016-10-17 23:30 +0200
    Re: [PATCH v9 10/12] vfio: Add function to get device_api string  from vfio_device_info.flags Alex Williamson <alex.williamson@redhat.com> - 2016-10-20 21:40 +0200
      Re: [PATCH v9 10/12] vfio: Add function to get device_api string from  vfio_device_info.flags Kirti Wankhede <kwankhede@nvidia.com> - 2016-10-20 22:40 +0200
        Re: [PATCH v9 10/12] vfio: Add function to get device_api string  from vfio_device_info.flags Alex Williamson <alex.williamson@redhat.com> - 2016-10-20 23:10 +0200
          Re: [PATCH v9 10/12] vfio: Add function to get device_api string from  vfio_device_info.flags Kirti Wankhede <kwankhede@nvidia.com> - 2016-10-20 23:20 +0200
            Re: [PATCH v9 10/12] vfio: Add function to get device_api string  from vfio_device_info.flags Alex Williamson <alex.williamson@redhat.com> - 2016-10-20 23:30 +0200
              Re: [PATCH v9 10/12] vfio: Add function to get device_api string from  vfio_device_info.flags Kirti Wankhede <kwankhede@nvidia.com> - 2016-10-21 05:10 +0200
                Re: [PATCH v9 10/12] vfio: Add function to get device_api string  from vfio_device_info.flags Alex Williamson <alex.williamson@redhat.com> - 2016-10-21 05:30 +0200
  [PATCH v9 02/12] vfio: VFIO based driver for Mediated devices Kirti Wankhede <kwankhede@nvidia.com> - 2016-10-17 23:30 +0200
    RE: [PATCH v9 02/12] vfio: VFIO based driver for Mediated devices "Tian, Kevin" <kevin.tian@intel.com> - 2016-10-26 09:00 +0200
      Re: [PATCH v9 02/12] vfio: VFIO based driver for Mediated devices Kirti Wankhede <kwankhede@nvidia.com> - 2016-10-26 17:10 +0200
  [PATCH v9 08/12] vfio_pci: Updated to use vfio_set_irqs_validate_and_prepare() Kirti Wankhede <kwankhede@nvidia.com> - 2016-10-17 23:30 +0200
  [PATCH v9 11/12] docs: Add Documentation for Mediated devices Kirti Wankhede <kwankhede@nvidia.com> - 2016-10-17 23:30 +0200
    Re: [PATCH v9 11/12] docs: Add Documentation for Mediated devices Alex Williamson <alex.williamson@redhat.com> - 2016-10-25 18:20 +0200
  [PATCH v9 09/12] vfio_platform: Updated to use vfio_set_irqs_validate_and_prepare() Kirti Wankhede <kwankhede@nvidia.com> - 2016-10-17 23:30 +0200
  [PATCH v9 04/12] vfio iommu: Add support for mediated devices Kirti Wankhede <kwankhede@nvidia.com> - 2016-10-17 23:30 +0200
    Re: [PATCH v9 04/12] vfio iommu: Add support for mediated devices Alex Williamson <alex.williamson@redhat.com> - 2016-10-19 23:10 +0200
      Re: [PATCH v9 04/12] vfio iommu: Add support for mediated devices Kirti Wankhede <kwankhede@nvidia.com> - 2016-10-20 22:20 +0200
        Re: [PATCH v9 04/12] vfio iommu: Add support for mediated devices Alex Williamson <alex.williamson@redhat.com> - 2016-10-24 04:40 +0200
          RE: [PATCH v9 04/12] vfio iommu: Add support for mediated devices "Tian, Kevin" <kevin.tian@intel.com> - 2016-10-26 09:30 +0200
            Re: [PATCH v9 04/12] vfio iommu: Add support for mediated devices Kirti Wankhede <kwankhede@nvidia.com> - 2016-10-26 17:10 +0200
      RE: [PATCH v9 04/12] vfio iommu: Add support for mediated devices "Tian, Kevin" <kevin.tian@intel.com> - 2016-10-26 10:00 +0200
        Re: [PATCH v9 04/12] vfio iommu: Add support for mediated devices Alex Williamson <alex.williamson@redhat.com> - 2016-10-26 17:30 +0200
      RE: [PATCH v9 04/12] vfio iommu: Add support for mediated devices "Tian, Kevin" <kevin.tian@intel.com> - 2016-10-26 10:00 +0200
        Re: [PATCH v9 04/12] vfio iommu: Add support for mediated devices Alex Williamson <alex.williamson@redhat.com> - 2016-10-26 17:20 +0200
    Re: [PATCH v9 04/12] vfio iommu: Add support for mediated devices Jike Song <jike.song@intel.com> - 2016-10-21 10:00 +0200
      Re: [PATCH v9 04/12] vfio iommu: Add support for mediated devices Alex Williamson <alex.williamson@redhat.com> - 2016-10-21 16:40 +0200
        Re: [PATCH v9 04/12] vfio iommu: Add support for mediated devices Kirti Wankhede <kwankhede@nvidia.com> - 2016-10-24 12:40 +0200
  [PATCH v9 06/12] vfio_pci: Update vfio_pci to use vfio_info_add_capability() Kirti Wankhede <kwankhede@nvidia.com> - 2016-10-17 23:30 +0200
    Re: [PATCH v9 06/12] vfio_pci: Update vfio_pci to use  vfio_info_add_capability() Alex Williamson <alex.williamson@redhat.com> - 2016-10-20 21:30 +0200
      Re: [PATCH v9 06/12] vfio_pci: Update vfio_pci to use  vfio_info_add_capability() Kirti Wankhede <kwankhede@nvidia.com> - 2016-10-24 23:30 +0200
        Re: [PATCH v9 06/12] vfio_pci: Update vfio_pci to use  vfio_info_add_capability() Alex Williamson <alex.williamson@redhat.com> - 2016-10-24 23:40 +0200
  [PATCH v9 03/12] vfio: Rearrange functions to get vfio_group from dev Kirti Wankhede <kwankhede@nvidia.com> - 2016-10-17 23:30 +0200
    Re: [PATCH v9 03/12] vfio: Rearrange functions to get vfio_group  from dev Alex Williamson <alex.williamson@redhat.com> - 2016-10-19 19:30 +0200
  [PATCH v9 05/12] vfio: Introduce common function to add capabilities Kirti Wankhede <kwankhede@nvidia.com> - 2016-10-17 23:30 +0200
    Re: [PATCH v9 05/12] vfio: Introduce common function to add  capabilities Alex Williamson <alex.williamson@redhat.com> - 2016-10-20 21:30 +0200
      Re: [PATCH v9 05/12] vfio: Introduce common function to add  capabilities Kirti Wankhede <kwankhede@nvidia.com> - 2016-10-24 23:30 +0200
        Re: [PATCH v9 05/12] vfio: Introduce common function to add  capabilities Alex Williamson <alex.williamson@redhat.com> - 2016-10-24 23:40 +0200
  [PATCH v9 01/12] vfio: Mediated device Core driver Kirti Wankhede <kwankhede@nvidia.com> - 2016-10-17 23:30 +0200
    Re: [PATCH v9 01/12] vfio: Mediated device Core driver Alex Williamson <alex.williamson@redhat.com> - 2016-10-19 01:20 +0200
      Re: [PATCH v9 01/12] vfio: Mediated device Core driver Kirti Wankhede <kwankhede@nvidia.com> - 2016-10-19 21:20 +0200
        Re: [PATCH v9 01/12] vfio: Mediated device Core driver Alex Williamson <alex.williamson@redhat.com> - 2016-10-20 00:30 +0200
    Re: [PATCH v9 01/12] vfio: Mediated device Core driver Jike Song <jike.song@intel.com> - 2016-10-20 09:30 +0200
      Re: [PATCH v9 01/12] vfio: Mediated device Core driver Alex Williamson <alex.williamson@redhat.com> - 2016-10-20 19:20 +0200
        Re: [PATCH v9 01/12] vfio: Mediated device Core driver Jike Song <jike.song@intel.com> - 2016-10-21 04:50 +0200
    RE: [PATCH v9 01/12] vfio: Mediated device Core driver "Tian, Kevin" <kevin.tian@intel.com> - 2016-10-26 09:00 +0200
      Re: [PATCH v9 01/12] vfio: Mediated device Core driver Kirti Wankhede <kwankhede@nvidia.com> - 2016-10-26 17:00 +0200
  Re: [PATCH v9 00/12] Add Mediated device support Alex Williamson <alex.williamson@redhat.com> - 2016-10-17 23:50 +0200
  Re: [PATCH v9 12/12] docs: Sample driver to demonstrate how to use  Mediated device framework. Alex Williamson <alex.williamson@redhat.com> - 2016-10-18 19:20 +0200
    Re: [PATCH v9 12/12] docs: Sample driver to demonstrate how to use  Mediated device framework. Kirti Wankhede <kwankhede@nvidia.com> - 2016-10-19 21:20 +0200
  Re: [PATCH v9 00/12] Add Mediated device support Jike Song <jike.song@intel.com> - 2016-10-24 09:20 +0200

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