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Re: [Qemu-devel] [PATCH v2 2/6] memory: Add IOMMU_ATTR_VFIO_NESTED IOMMU


From: Auger Eric
Subject: Re: [Qemu-devel] [PATCH v2 2/6] memory: Add IOMMU_ATTR_VFIO_NESTED IOMMU memory region attribute
Date: Wed, 3 Jul 2019 11:10:26 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0

Hi Peter,

On 7/3/19 7:42 AM, Peter Xu wrote:
> On Mon, Jul 01, 2019 at 11:30:30AM +0200, Eric Auger wrote:
>> We introduce a new IOMMU Memory Region attribute,
>> IOMMU_ATTR_VFIO_NESTED that tells whether the virtual IOMMU
>> requires physical nested stages for VFIO integration.
>>
>> Current Intel virtual IOMMU device supports "Caching
>> Mode" and does not require 2 stages at physical level to be
>> integrated with VFIO. However SMMUv3 does not implement such
>> "caching mode" and requires to use physical stage 1 for VFIO
>> integration.
>>
>> Signed-off-by: Eric Auger <address@hidden>
>> ---
>>  include/exec/memory.h | 3 ++-
>>  1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/include/exec/memory.h b/include/exec/memory.h
>> index bdd76653a8..dd7ef23f96 100644
>> --- a/include/exec/memory.h
>> +++ b/include/exec/memory.h
>> @@ -204,7 +204,8 @@ struct MemoryRegionOps {
>>  };
>>  
>>  enum IOMMUMemoryRegionAttr {
>> -    IOMMU_ATTR_SPAPR_TCE_FD
>> +    IOMMU_ATTR_SPAPR_TCE_FD,
>> +    IOMMU_ATTR_VFIO_NESTED,
> 
> IMHO it'll be better if this patch can be squashed into the first user
> of the new flag to better clarify itself on why it will be needed (if
> finally we still would like to have this flag).
sure I will squash it.

Nested mode requires important adaptations in the current
hw/vfio/common.c code to register specific notifiers: UNMAP, config
change, MSI binding notifiers (this one actually uses a MAP notifier by
the way). So there we need to recognize an IOMMU works in nested mode
one way or another.

Thanks

Eric
> 
> Regards,
> 



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