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From: Paolo Bonzini <pbonzini@redhat.com>
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Date: Fri, 17 Jul 2015 15:50:25 +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>
Cc: Linhaifeng <haifeng.lin@huawei.com>, "Michael S. Tsirkin" <mst@redhat.com>, Thibaut Collet <thibaut.collet@6wind.com>, jasowang@redhat.com, QEMU <qemu-devel@nongnu.org>, stefanha@redhat.com



On 17/07/2015 15:35, Marc-Andr=C3=A9 Lureau wrote:
>> > LOG_FD is implemented in the kernel drivers/vhost/vhost.c.  It seems=
 to
>> > be an eventfd-like mechanism to save on dirty bitmap scans.  However=
,
>> > it's not well documented how to implement it in a correct way.
> and it's not used by qemu, so hard to say if it actually work well.
>=20
> > In any case, live migration needs a new message type (like LOG_MMAP_F=
D)
> > in the vhost-user protocol.
>
> Yes, perhaps with size and offset. I am looking at this.

The offset should be 0...

Do you know the size of the ram_addr_t space from
VHOST_USER_SET_MEM_TABLE's user address and size fields?

If the size isn't needed, you can reuse LOG_BASE, ignoring the content
of the payload and adding the SCM_RIGHTS file descriptor.

Paolo