Re: [Qemu-devel] [PATCH v4 1/1] vhost user: add support of live migration

[Marc-André Lureau]

Hi

On Mon, Jul 13, 2015 at 4:27 AM, Linhaifeng <address@hidden> wrote:
>> When a packet is received by vhost-user, the vhost-user writes the
>> packet in guest memory.  QEMU must then copy that page of guest memory
>> from source to destination; it uses a dirty bitmap for this purpose.
>>
>> How does vhost-user do this?  I can see this patch providing enough
>> support for *non*live migration.  However, it cannot be enough for live
>> migration unless I'm missing something obvious.
>>
>> Paolo
>
> Agree. vhost-user should mmap the log memory and mark dirty pages when send
> or receive packets.

This is already supported by vhost-user protocol, isn't it? The
LOG_BASE/FD and vring log_guest_addr are provided. I can't find any
vhost-user backend implementing dirty bitmaps yet though, but it looks
like it should work. I suppose the backend should stop all IO after
RESET_OWNER is received.

-- 
Marc-André Lureau