Re: [PATCH v2 19/24] vdpa: make sure set_features in invoked for legacy

On 2020/8/5 下午7:40, Michael S. Tsirkin wrote:

On Wed, Aug 05, 2020 at 02:14:07PM +0800, Jason Wang wrote:

quoted

On 2020/8/4 上午5:00, Michael S. Tsirkin wrote:

quoted

Some legacy guests just assume features are 0 after reset.
We detect that config space is accessed before features are
set and set features to 0 automatically.
Note: some legacy guests might not even access config space, if this is
reported in the field we might need to catch a kick to handle these.

I wonder whether it's easier to just support modern device?

Thanks

Well hardware vendors are I think interested in supporting legacy
guests. Limiting vdpa to modern only would make it uncompetitive.

My understanding is that, IOMMU_PLATFORM is mandatory for hardware vDPA 
to work. So it can only work for modern device ...

Thanks

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