Re: [PATCH v3 0/2] s390/mm: shared zeropage + KVM fixes

Andrew Morton
2024-04-11T21:28:29Z

On Thu, 11 Apr 2024 18:14:39 +0200 David Hildenbrand <david@redhat.com> wrote:

> This series fixes one issue with uffd + shared zeropages on s390x and
> fixes that "ordinary" KVM guests can make use of shared zeropages again.
>
> ...
>
> Without the shared zeropage, during (2), the VM would suddenly consume
> 100 GiB on the migration source and destination. On the migration source,
> where we don't excpect memory overcommit, we could easilt end up crashing
> the VM during migration.
>
> Independent of that, memory handed back to the hypervisor using "free page
> reporting" would end up consuming actual memory after the migration on the
> destination, not getting freed up until reused+freed again.
>

Is a backport desirable?

If so, the [1/2] Fixes dates back to 2015 and the [2/2] Fixes is from
2017. Is it appropriate that the patches be backported so far back,
and into different kernel versions?