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

From: Jason Wang
Date: Wed Aug 05 2020 - 23:23:19 EST

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

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 ...