Re: [PATCH v3 2/2] vhost: Only align sections for vhost-user

[Paolo Bonzini]

On 17/01/20 14:40, Michael S. Tsirkin wrote:
> We don't really need v2 just to add a field. Compatibility is maintained
> using feature bits. Adding that is a subject for another patch.
> But I'm not sure I understand why does remote need to know about alignment.
> This patch seems to handle it locally ...

Because the remote vhost here will not be able to use the synic regions.
 If it did, it would have the same overlap problem as vhost-kernel.

The alignment is needed because, even if you are mapping only [768k,1M)
of a 2M hugepage, you need to mmap [0,2M).  You can then discard the
rest, but IIUC if you only mmap [768k,1M) then the kernel will fail the
mmap.

Paolo