Re: [PATCH V2] docs: vhost-user: Add Xen specific memory mapping support

[Viresh Kumar <viresh.kumar@xxxxxxxxxx>]

On 07-03-23, 11:22, Stefan Hajnoczi wrote:
> VHOST_USER_IOTLB_MSG probably isn't necessary because address
> translation is not required. It will also reduce performance by adding
> extra communication.
> 
> Instead, you could change the 1 memory region : 1 mmap relationship that
> existing non-Xen vhost-user back-end implementations have. In Xen
> vhost-user back-ends, the memory region details (including the file
> descriptor and Xen domain id) would be stashed away in back-end when the
> front-end adds memory regions. No mmap would be performed upon
> VHOST_USER_ADD_MEM_REG or VHOST_USER_SET_MEM_TABLE.
> 
> Whenever the back-end needs to do DMA, it looks up the memory region and
> performs the mmap + Xen-specific calls:
> - A long-lived mmap of the vring is set up when
>   VHOST_USER_SET_VRING_ENABLE is received.
> - Short-lived mmaps of the indirect descriptors and memory pointed to by
>   the descriptors is set up by the virtqueue processing code.
> 
> Does this sound workable to you?

Sounds good. I have sent a proposal (v3) based on that now.

-- 
viresh