Re: (proposal) RE: [PATCH v7 00/16] vfio: expose virtual Shared Virtual Addressing to VMs

Jason Wang
2020-10-21T02:21:38Z

On 2020/10/20 下午10:19, Liu, Yi L wrote:
>> From: Jason Gunthorpe <jgg@nvidia.com>
>> Sent: Tuesday, October 20, 2020 10:02 PM
> [...]
>>>> Whoever provides the vIOMMU emulation and relays the page fault to the
>> guest
>>>> has to translate the RID -
>>> that's the point. But the device info (especially the sub-device info) is
>>> within the passthru framework (e.g. VFIO). So page fault reporting needs
>>> to go through passthru framework.
>>>
>>>> what does that have to do with VFIO?
>>>>
>>>> How will VPDA provide the vIOMMU emulation?
>>> a pardon here. I believe vIOMMU emulation should be based on IOMMU
>> vendor
>>> specification, right? you may correct me if I'm missing anything.
>> I'm asking how will VDPA translate the RID when VDPA triggers a page
>> fault that has to be relayed to the guest. VDPA also has virtual PCI
>> devices it creates.
> I've got a question. Does vDPA work with vIOMMU so far? e.g. Intel vIOMMU
> or other type vIOMMU.

The kernel code is ready. Note that vhost suppport for vIOMMU is even
earlier than VFIO.

The API is designed to be generic is not limited to any specific type of
vIOMMU.

For qemu, it just need a patch to implement map/unmap notifier as what
VFIO did.

Thanks

>
> Regards,
> Yi Liu