On 8/4/2026 5:46 PM, Shradha Gupta wrote:
On Tue, Jul 28, 2026 at 01:51:14PM +0000, Naman Jain wrote:
On CPU hot-unplug, fixup_irqs() re-injects interrupts that are still
pending in the outgoing CPU's IRR via the irqchip's irq_retrigger()
callback. The Hyper-V vPCI MSI irqchip never installs one, so such a
pending interrupt is silently dropped, leading to lost interrupts, stalls
and "No irq handler for vector" messages.
Patch 1 is the minimal, backportable fix (Fixes:/Cc: stable) that installs
irq_chip_retrigger_hierarchy() on the Hyper-V PCI/MSI chip. Patch 2 then
switches fixup_irqs() to call irq_chip_retrigger_hierarchy() directly, so
the retrigger works for any stacked irqchip without a per-chip callback.
Patch 3 drops the now-redundant irq_retrigger() initializations.
This way, patch 2 and 3 do not need to be backported.
Thanks Naman, the series looks good to me.
I just have a small nit. In the old code, VECTOR_RETRIGGERED is set
unconditionally after calling chip->irq_retrigger(), regardless of its
return value. In the new code, VECTOR_RETRIGGERED is only set when
irq_chip_retrigger_hierarchy() returns non-zero. So retrigger failures
would now result in VECTOR_UNUSED instead of VECTOR_RETRIGGERED.
In practice this doesn't matter since apic_retrigger_irq() always returns
1, but it is technically a behavior change and I think it is a correct
one. Just that it might be worth noting this in the commit message to
avoid confusion.
Reviewed-by: Shradha Gupta <[email protected]>
Thank you Shradha. I'll address this in the next patch version.
Regards,
Naman
