On 2018/12/13 下午10:31, Michael S. Tsirkin wrote:

quoted

Just to make sure I understand this. It looks to me we should:

- allow passing GIOVA->GPA through UAPI

- cache GIOVA->GPA somewhere but still use GIOVA->HVA in device IOTLB for
performance

Is this what you suggest?

Thanks

Not really. We already have GPA->HVA, so I suggested a flag to pass
GIOVA->GPA in the IOTLB.

This has advantages for security since a single table needs
then to be validated to ensure guest does not corrupt
QEMU memory.

I wonder how much we can gain through this. Currently, qemu IOMMU gives 
GIOVA->GPA mapping, and qemu vhost code will translate GPA to HVA then 
pass GIOVA->HVA to vhost. It looks no difference to me.

Thanks