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Date: Wed, 20 Mar 2013 11:57:14 +0000
From: David Scott <dave.scott@eu.citrix.com>
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Subject: Re: [Qemu-devel] [Xen-devel] [PATCHv3] QEMU(upstream): Disable
 xen's use of O_DIRECT by default as it results in crashes.
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To: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Cc: Ian Campbell <Ian.Campbell@citrix.com>, George Dunlap <George.Dunlap@eu.citrix.com>, Ian Jackson <Ian.Jackson@eu.citrix.com>, "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>, xen-devel <xen-devel@lists.xen.org>, Alex Bligh <alex@alex.org.uk>, Anthony Liguori <anthony@codemonkey.ws>, Paolo Bonzini <pbonzini@redhat.com>

Hi,

On 20/03/13 10:24, Stefano Stabellini wrote:

> That is true. My guess is that nobody really migrates HVM guests without
> PV drivers installed (it's not even possible on XenServer but xl let you
> do that if you want to). When the PV drivers initialize at boot time,
> the IDE disk is closed. Therefore we wouldn't have this problem.
>
> Maybe we should prevent HVM guest migration without PV drivers with xl
> too. Ian, what do you think?

Although it's not normally possible on XenServer to migrate HVM guests 
without PV drivers, a lot of people override the check and do it anyway. 
It happens a lot in cloud scenarios where the host (XenServer) admin is 
different from the guest admin (the end customer) and it's impractical 
for the host admin to force the guest admin to load the drivers.

We do our best to recommend, encourage and help people to install HVM PV 
drivers but we have to tolerate those who ignore our advice :/

Cheers,
Dave