[PATCH 0/2] Re-raise irq_work lost during Xen suspend

[Julian Vetter <julian.vetter@xxxxxxxxxx>]

We hit this issue with an Ubuntu 26.04 cloudimage guests (7.0 based
kernel with the 8250 as an nbcon console) on XCP-ng 8.3 / Xen 4.17. With
a kernel commandline adding two consoles, i.e., 'console=ttyS1
console=ttyS0'. During a live migration on that setup the printk()s from
gnttab_resume() and xen_irq_resume() queue nbcon_irq_work while the APIC
is disabled. Thus the list transitions from empty to non-empty, but
doesn't receive the IPI to empty the list again. Afterwards the list
stays non-empty, so the IPI never fires and all irq_work piles up.

The Commit 560f4deda327 ("printk/nbcon: Change nbcon_irq_work to
IRQ_WORK_LAZY") removed this particular issue because declaring the IRQ
work to be lazy, causes the timer interrupt to trigger the irq work
instead. But any other non-lazy irq_work queued in that window is still
lost the same way and will cause the list to fill up without being
handled.

Signed-off-by: Julian Vetter <julian.vetter@xxxxxxxxxx>
---
Julian Vetter (2):
  irq_work: Add irq_work_raise_pending()
  xen/manage: Re-raise pending irq_work after suspend

 drivers/xen/manage.c     |  3 +++
 include/linux/irq_work.h |  2 ++
 kernel/irq_work.c        | 10 ++++++++++
 3 files changed, 15 insertions(+)

-- 
2.53.0



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Julian Vetter | Vates Hypervisor & Kernel Developer

XCP-ng & Xen Orchestra - Vates solutions

web: https://vates.tech