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From: Paolo Bonzini <pbonzini@redhat.com>
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Date: Fri, 17 Jul 2015 04:25:57 +0200
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Subject: Re: [Qemu-devel] [PATCH v4 1/1] vhost user: add support of live
 migration
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To: =?UTF-8?Q?Marc-Andr=c3=a9_Lureau?= <marcandre.lureau@gmail.com>, Linhaifeng <haifeng.lin@huawei.com>
Cc: Thibaut Collet <thibaut.collet@6wind.com>, jasowang@redhat.com, QEMU <qemu-devel@nongnu.org>, stefanha@redhat.com, "Michael S. Tsirkin" <mst@redhat.com>



On 17/07/2015 02:19, Marc-Andr=C3=A9 Lureau wrote:
>>> >> How does vhost-user do this?  I can see this patch providing enoug=
h
>>> >> 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 wh=
en 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.

But LOG_BASE makes little sense across processes, and LOG_FD is unused
in QEMU, isn't it?  So this patch is not enough to add support of live
migration.

Paolo