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[PATCH v1 0/2] domctl: Avoid taking domctl lock for certain ops used during migration
- To: xen-devel@xxxxxxxxxxxxxxxxxxxx
- From: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
- Date: Tue, 9 Jun 2026 16:15:26 +0100
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- Cc: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>, Jan Beulich <jbeulich@xxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Teddy Astie <teddy.astie@xxxxxxxxxx>, Anthony PERARD <anthony.perard@xxxxxxxxxx>, Michal Orzel <michal.orzel@xxxxxxx>, Julien Grall <julien@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, "Daniel P. Smith" <dpsmith@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Tue, 09 Jun 2026 15:15:41 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
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(-)
--
2.53.0
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