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From: Stefan Hajnoczi <stefanha@gmail.com>
Date: Thu, 13 Oct 2016 07:15:30 +0200
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Subject: Re: [Qemu-devel] Async savevm using userfaultfd(2)
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To: qemu-devel <qemu-devel@nongnu.org>
Cc: John Snow <jsnow@redhat.com>, "Denis V. Lunev" <den@openvz.org>, Rik van Riel <riel@redhat.com>, Andrea Arcangeli <aarcange@redhat.com>, "Dr. David Alan Gilbert" <dgilbert@redhat.com>

On Wed, Oct 12, 2016 at 4:04 PM, Stefan Hajnoczi <stefanha@gmail.com> wrote:
> Perhaps this approach can be prototyped with mprotect and a SIGSEGV
> handler if anyone wants to get async savevm going.  I don't know if
> there are any disadvantages to mprotecting guest RAM that the kvm kernel
> module is using.  Hopefully in-kernel devices and vhost will continue to
> work.

I woke up this morning with a strong feeling that a SIGSEGV handler
won't work with vhost.  The problem is that the QEMU process' SIGSEGV
handler won't be called when the vhost kernel thread faults.  Now I'm
wondering whether userfaultfd will work together with vhost.

Stefan