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Date: Sun, 17 Aug 2014 08:08:14 +0200
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] [RFC 2/3] QMP: rate limit BLOCK_IO_ERROR
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To: "Daniel P. Berrange" <berrange@redhat.com>, Markus Armbruster <armbru@redhat.com>
Cc: kwolf@redhat.com, qemu-devel@nongnu.org, Luiz Capitulino <lcapitulino@redhat.com>

Il 11/08/2014 13:15, Daniel P. Berrange ha scritto:
>> > 1. Don't throttle.  Client can rely on events as long as it keeps the
>> >    QMP connection alive.  Client should poll after establishing the QMP
>> >    connection.
> A malicious guest OS can flood libvirt with events in this way. Of course
> even if we throttle, a compromised QEMU can still flood libvirt. The only
> fail-safe protection is for libvirt to detect flooding and throttle the
> rate at which it talks to the (malicious) QEMU.
> 

If you use rerror=stop,werror=stop, only a limited error can be passed
down to libvirt before libvirt invokes the "cont" command and there's no
need to do any throttling.

Paolo