Virtualization - May 2022 - [PATCH 0/3] recover hardware corrupted page by virtio balloon

On Wed, May 25, 2022 at 01:16:34PM -0700, Jue Wang
wrote:
> The hypervisor _must_ emulate poisons identified in guest physical
> address space (could be transported from the source VM), this is to
> prevent silent data corruption in the guest. With a paravirtual
> approach like this patch series, the hypervisor can clear some of the
> poisoned HVAs knowing for certain that the guest OS has isolated the
> poisoned page. I wonder how much value it provides to the guest if the
> guest and workload are _not_ in a pressing need for the extra KB/MB
> worth of memory.
I'm curious the same on how unpoisoning could help here.  The reasoning
behind would be great material to be mentioned in the next cover letter.

Shouldn't we consider migrating serious workloads off the host already
where there's a sign of more severe hardware issues, instead?

Thanks,

-- 
Peter Xu

On 5/27/22 02:37, Peter Xu wrote:
> On Wed, May 25, 2022 at 01:16:34PM -0700, Jue Wang wrote:
>> The hypervisor _must_ emulate poisons identified in guest physical
>> address space (could be transported from the source VM), this is to
>> prevent silent data corruption in the guest. With a paravirtual
>> approach like this patch series, the hypervisor can clear some of the
>> poisoned HVAs knowing for certain that the guest OS has isolated the
>> poisoned page. I wonder how much value it provides to the guest if the
>> guest and workload are _not_ in a pressing need for the extra KB/MB
>> worth of memory.
> 
> I'm curious the same on how unpoisoning could help here.  The reasoning
> behind would be great material to be mentioned in the next cover letter.
> 
> Shouldn't we consider migrating serious workloads off the host already
> where there's a sign of more severe hardware issues, instead?
> 
> Thanks,
> 
I'm maintaining 1000,000+ virtual machines, from my experience:
UE is quite unusual and occurs randomly, and I did not hit UE storm case 
in the past years. The memory also has no obvious performance drop after 
hitting UE.

I hit several CE storm case, the performance memory drops a lot. But I 
can't find obvious relationship between UE and CE.

So from the point of my view, to fix the corrupted page for VM seems 
good enough. And yes, unpoisoning several pages does not help 
significantly, but it is still a chance to make the virtualization better.

-- 
zhenwei pi