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

On Thu, Aug 06, 2020 at 11:23:05AM +0800, Jason Wang wrote:

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

quoted

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.

Hmm I don't really see why. Assume host maps guest memory properly,
VM does not have an IOMMU, legacy guest can just work.

Care explaining what's wrong with this picture?

So it can only work for modern device ...

Thanks

quoted

_______________________________________________
Virtualization mailing list
Virtualization@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/virtualization