From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Michael S. Tsirkin" <mst@redhat.com>
Subject: Re: hotplug: VM got stuck when attaching a pass-through device to
 the non-pass-through VM for the first time
Date: Tue, 18 Feb 2014 13:16:15 +0200
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Cc: "Zhanghaoyu (A)" <haoyu.zhang@huawei.com>,
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To: Paolo Bonzini <pbonzini@redhat.com>
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On Tue, Feb 18, 2014 at 12:05:19PM +0100, Paolo Bonzini wrote:
> Il 18/02/2014 11:51, Michael S. Tsirkin ha scritto:
> >>> I agree it's either COW breaking or (similarly) locking pages that
> >>> the guest hasn't touched yet.
> >>>
> >>> You can use prealloc or "-rt mlock=on" to avoid this problem.
> >>>
> >>> Paolo
> >Or the new shared flag - IIRC shared VMAs don't do COW either.
> 
> Only if the problem isn't locking and zeroing of untouched pages
> (also, it is not upstream is it?).

No but it's a small patch - part of vhost user patchset.

> Can you make a profile with perf?
> 
> Paolo