Re: [Qemu-devel] [PATCH v4 2/5] memory: Add IOMMU_ATTR_HW_NESTED_PAGING IOMMU memory region attribute

[Auger Eric <eric.auger@redhat.com>]

Hi Peter,

On 8/27/19 6:19 PM, Peter Maydell wrote:
> On Thu, 22 Aug 2019 at 18:24, Eric Auger <eric.auger@redhat.com> wrote:
>>
>> We introduce a new IOMMU Memory Region attribute,
>> IOMMU_ATTR_HW_NESTED_PAGING that tells whether the virtual
>> IOMMU relies on physical IOMMU HW nested paging capability
>> when protecting host assigned devices.
> 
> I'm still not really happy with the name of this attribute.
> "IOMMU_ATTR_HW_NESTED_PAGING" sounds like it ought to mean
> "true if this IOMMU supports/is using hardware nested paging". What
> your commit message suggests it means is "true if this IOMMU
> *needs* hardware nested paging", but there's no NEEDS in the
> attribute name.

OK I will respin and add "_NEED_".

Thanks

Eric
> 
>> 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 HW nested paging.
>>
>> As such SMMUv3 is the first IOMMU device to advertise this
>> attribute.
>>
>> Signed-off-by: Eric Auger <eric.auger@redhat.com>
> 
> The code changes look good to me though.
> 
> thanks
> -- PMM
>