Re: [PATCH v1 0/2] domctl: Avoid taking domctl lock for certain ops used during migration

[Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>]

On 6/10/26 11:57 AM, Ross Lagerwall wrote:
> On 6/9/26 4:15 PM, Ross Lagerwall wrote:
> > When performing multiple migrations in parallel, the domctl lock may
> > become extremely contended:
> >
> > * Operations like "xl vcpu-list" were observed to take in excess of 20s
> >    to execute.
> > * The "clean" shadow op may pause the domain, restart with a
> >    continuation and then become blocked on the domctl lock, causing VM
> >    downtime in excess of 20 seconds.
> >
> > These issues can be fixed by not holding the domctl for the frequently
> > called operations during migration.
> >
> > Thanks
> >
> > Ross Lagerwall (2):
> >    domctl: Handle XEN_DOMCTL_getpageframeinfo3 without the domctl lock
> >    domctl: Handle some of XEN_DOMCTL_shadow_op without the domctl lock
> >
> >   xen/arch/x86/domctl.c    |  4 ++++
> >   xen/arch/x86/mm/paging.c |  8 ++++++--
> >   xen/common/domctl.c      | 13 +++++++++++++
> >   3 files changed, 23 insertions(+), 2 deletions(-)
> I'd like to request inclusion of this in 4.22 since it fixes a real
> customer issue we have observed and would have been posted some time ago
> but was delayed to avoid drawing attention to and colliding with
> XSA-492.
Considering this and performance improvements it would be really nice to 
have in in 4.22:
 Release-Acked-by: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>

Thanks.

~ Oleksii