Re: [Qemu-devel] [PATCH 0/2] memory/intel_iommu: Generate error for incompatible usage

[Alex Williamson <alex.williamson@redhat.com>]

On Wed, 29 Jun 2016 12:53:39 +0200
Paolo Bonzini <pbonzini@redhat.com> wrote:

> On 28/06/2016 16:49, Alex Williamson wrote:
> > Paolo & Michael,
> > 
> > Any comments on this series?  I think we need Paolo's ack for the memory
> > changes and either of your ack for hw/i386/.  I'm happy to pull this
> > through my tree with your approval though.  Thanks,  
> 
> I think I already acked the callbacks, in any case the patches look good.

Hmm, I can't find any evidence of that and I'm not terribly comfortable
inferring an Acked-by where it is not explicitly given.  Can you send
a formal sign-off or point me to where I can find the one you're
thinking of?  Thanks,

Alex

> > On Wed, 15 Jun 2016 09:56:03 -0600
> > Alex Williamson <alex.williamson@redhat.com> wrote:
> >   
> >> VT-d emulation is currently incompatible with device assignment due
> >> to intel_iommu's lack of support for memory_region_notify_iommu().
> >> Alexey has proposed a nice addition to the MemoryRegionIOMMUOps
> >> structure that adds callbacks when the first iommu notifier is
> >> registered and the last is removed.  For POWER this will allow them
> >> to switch the view of the iommu depending on whether anyone in
> >> userspace is watching.  For VT-d I expect that eventually we'll use
> >> these callbacks to enable and disable code paths so that we avoid
> >> notifier overhead when there are no registered notifiy-ees.  For now,
> >> we don't support calling memory_region_notify_iommu(), so this
> >> signals an incompatible hardware configuration.  If we choose to make
> >> CM=0 a user selectable option, something like this might continue to
> >> be useful if we only support notifies via invalidations rather than
> >> full VT-d data structure shadowing.
> >>
> >> Even though we're currently working on enabling users like vfio-pci
> >> with VT-d, I believe this is correct for the current state of things.
> >> We might even want to consider this stable for v2.6.x so that
> >> downstreams pick it up to avoid incompatible configurations.
> >>
> >> Alexey, I hope I'm not stepping on your toes by extracting this
> >> from your latest patch series.  Please let us know whether you
> >> approve.  Thanks,
> >>
> >> Alex
> >>
> >> ---
> >>
> >> Alex Williamson (1):
> >>       intel_iommu: Throw hw_error on notify_started
> >>
> >> Alexey Kardashevskiy (1):
> >>       memory: Add MemoryRegionIOMMUOps.notify_started/stopped callbacks
> >>
> >>
> >>  hw/i386/intel_iommu.c |   12 ++++++++++++
> >>  hw/vfio/common.c      |    5 +++--
> >>  include/exec/memory.h |    8 +++++++-
> >>  memory.c              |   10 +++++++++-
> >>  4 files changed, 31 insertions(+), 4 deletions(-)  
> >