Re: Re: [PATCH][HVM] fix VNIF restore failure on HVMguestwith heavy workload

["Steven Hand" <steven.hand@cl.cam.ac.uk>]

Just FYI - this is something I tested successfully last week. Not sure
if anything has been changed in recent changesets but worth checking
up - can you post the output from /var/log/xen/xend.log ?

Secondly: there is a known issue with save/restore of ballooned domains
(HVM or PV) where the balloning is done from within the guest (e.g.
by echoing to /proc/xen/balloon). Since this doesn't update the memory
target within xenstore, you'll end up 'reverting' the guest memory size to
that last set via xm mem-set. The 'fix' is not to do that, i.e. only use the
xm or XenAPI to request ballooning.


cheers,

S.




----- Original Message ----- 
From: "Zhao, Fan" <fan.zhao@intel.com>
To: "Keir Fraser" <keir@xensource.com>; "Zhai, Edwin" <edwin.zhai@intel.com>
Cc: "Tim Deegan" <Tim.Deegan@xensource.com>; "Ian Pratt" 
<Ian.Pratt@cl.cam.ac.uk>; <xen-devel@lists.xensource.com>
Sent: Wednesday, April 11, 2007 5:24 PM
Subject: RE: [Xen-devel] Re: [PATCH][HVM] fix VNIF restore failure on 
HVMguestwith heavy workload


Hi Keir,
I noticed that with cset 14773, if I use xm mem-set to adjust the memory of 
hvm guest with balloon driver by xm mem-set, and then save the guest, the xm 
save will fail, so does xm migrate. A white window will pop up, and the 
guest still exists through xm li. So will your great fixes also include the 
fixing for this issue? Thanks!

Best regards,
Fan

-----Original Message-----
From: xen-devel-bounces@lists.xensource.com 
[mailto:xen-devel-bounces@lists.xensource.com] On Behalf Of Keir Fraser
Sent: 2007Äê4ÔÂ11ÈÕ 16:57
To: Zhai, Edwin
Cc: Tim Deegan; Ian Pratt; xen-devel@lists.xensource.com
Subject: Re: [Xen-devel] Re: [PATCH][HVM] fix VNIF restore failure on 
HVMguest with heavy workload


FYI, the next changeset worth testing or fixing is r14795:6e7ef794cdbc. I've
made a *lot* of changes in the last 24 hours. I've tried a few save/restores
under block and net load with no observed problems.

 -- Keir

On 11/4/07 08:20, "Zhai, Edwin" <edwin.zhai@intel.com> wrote:

> On Tue, Apr 10, 2007 at 08:16:04PM +0100, Keir Fraser wrote:
>> On 10/4/07 17:47, "Zhai, Edwin" <edwin.zhai@intel.com> wrote:
>>
>>> [PATCH][HVM] fix VNIF restore failure on HVM guest with heavy workload
>>>
>>> Signed-off-by: Zhai Edwin <edwin.zhai@intel.com>
>>>
>>> VNIF has many intrs when save/restore with net workload, so need keep
>>> handler
>>> from intrs
>>
>> What happens if an interrupt is being processed during save/restore? It
>> would be nice to know what the underlying bug is!
>
> If an pseudo PCI intr occurred after xen_suspend on cpu0, there is 
> definitely
> a
> crash. I copy this code from original PV driver code.
>
>>
>> That said, it may well make sense to somehow disable interrupt handling
>> across save/restore. Unfortunately your patch is insufficient since we 
>> could
>> handle event-channel interrupts on any VCPU (the irq's affinity can be
>> changed outside our control if it is routed through the virtual IOAPIC, 
>> and
>> if e.g. the userspace irqbalance daemon is running).
>>
>> I wanted to use stop_machine_run() but unfortunately it isn't exported to
>> modules. :-( irq_disable() may do the right thing for us though.
>
> SMP is a headache for PV drv save/restore on HVM. Even we disable intr on 
> all
> cpus, PV driver on other cpu may still access low level service after
> xen_suspend on cpu0.
>
> smp_suspend is used for PV drv on PV domain, which is not suitable for HVM 
> as
> we
> need the transparency to guest.
>
> Do we need lightweight stop_machine_run in this case, i.e. make other cpu
> sleep?
>
>
>>
>>  -- Keir
>>


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