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

[Paolo Bonzini <pbonzini@redhat.com>]

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.

Paolo

> 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(-)
>