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

From: Alexey Kardashevskiy
Subject: Re: [Qemu-devel] [PATCH 0/2] memory/intel_iommu: Generate error for incompatible usage
Date: Mon, 27 Jun 2016 14:46:12 +1000
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.1.1

On 16/06/16 11:43, Alexey Kardashevskiy wrote:
> On 16/06/16 01:56, Alex Williamson 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,
> I am totally fine with either way of accepting my patches, after all the
> idea was yours, I just put it in the code :)

Alex, when are you planning on sending pull request with this patch? I am
asking as I'd prefer to respin "spapr_pci/spapr_pci_vfio: Support Dynamic
DMA" on top of it (assuming David rebases his queue on top of it) and avoid
doing unnecessary work. 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(-)


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