[libvirt] [PATCH v2 06/11] docs: document cpu host-passthrough migration issue

Jason J. Herne jjherne at linux.vnet.ibm.com
Thu Dec 15 18:25:33 UTC 2016

On 12/15/2016 11:18 AM, Jiri Denemark wrote:
> On Fri, Dec 09, 2016 at 14:38:35 -0500, Jason J. Herne wrote:
>> Documents in formatdomain.html that when migrating a guest
>> defined with the host-passthrough CPU model from a machine that
>> is running on a newer CPU model than the destination machine's
>> CPU model, it is very likely that the guest will crash upon
>> arrival.
>> Signed-off-by: Jason J. Herne <jjherne at linux.vnet.ibm.com>
>> ---
>>  docs/formatdomain.html.in | 6 +++++-
>>  1 file changed, 5 insertions(+), 1 deletion(-)
>> diff --git a/docs/formatdomain.html.in b/docs/formatdomain.html.in
>> index 9218eec..b7c1e87 100644
>> --- a/docs/formatdomain.html.in
>> +++ b/docs/formatdomain.html.in
>> @@ -1292,7 +1292,11 @@
>>            understand. Though the downside of this mode is that the guest
>>            environment cannot be reproduced on different hardware. Thus, if you
>>            hit any bugs, you are on your own. Further details of that CPU can
>> -          be changed using <code>feature</code> elements.</dd>
>> +          be changed using <code>feature</code> elements. Migration of a guest
>> +          using host-passthrough is dangerous if the source and destination
>> +          hosts are not identical in both hardware and configuration. If such
>> +          a migration is attempted then the guest will very likely hang or
>> +          crash upon resuming execution on the destination host.</dd>
>>          </dl>
> I'd say "may" rather than "will very likely" :-) The likelihood of such
> behavior depends on a lot of factors, such as the host architecture, the
> way the hosts differ, etc. For example, on x86_64 such migration will
> work just fine as long as the destination host is not worse than the
> source host and even if it is, it depends on what the guest is doing.
> ACK and it can be pushed right away, just let me know whether you agree
> with the suggested change.
> Jirka

Hi Jiri,

Thanks for reviewing. Yes, we agree with your change to this. Let me 
know if you push it and we'll remove it from this series.

-- Jason J. Herne (jjherne at linux.vnet.ibm.com)

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