Re: [Xen-devel] Re: [PATCH][HVM] fix VNIF restore failure on HVM guest with heavy workload

[Keir Fraser <keir@xxxxxxxxxxxxx>]

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@xxxxxxxxx> wrote:

> On Tue, Apr 10, 2007 at 08:16:04PM +0100, Keir Fraser wrote:
>> On 10/4/07 17:47, "Zhai, Edwin" <edwin.zhai@xxxxxxxxx> wrote:
>> 
>>> [PATCH][HVM] fix VNIF restore failure on HVM guest with heavy workload
>>> 
>>> Signed-off-by: Zhai Edwin <edwin.zhai@xxxxxxxxx>
>>> 
>>> 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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