Re: [PATCH v6 0/4] x86/irq: Fix lost interrupts on CPU hot-unplug

[Naman Jain <namjain@linux.microsoft.com>]

On 9/23/2026 10:00 AM, 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 root partition PCI/MSI irqchip lost that callback
> when it was converted to msi_create_parent_irq_domain(), 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 restores
> irq_chip_retrigger_hierarchy() on the Hyper-V root partition PCI/MSI chip.
> The equivalent guest pci-hyperv.c fix from the previous version is already
> merged, so it is dropped here.
> 
> Patch 2 then switches fixup_irqs() to call irq_chip_retrigger_hierarchy()
> directly which ensures that this issue does not occur for chips that
> miss adding this initialization.
> 
> Patch 3 makes a similar change in msi_set_affinity()
> 
> Patch 4 then drops the now-redundant irq_retrigger() initializations.
> This way, patch 2-4 do not need to be backported.
> 

Hi Thomas, maintainers,
Gentle ping on this patch series. Please let me know if this is good to 
be picked in next merge cycle or if any changes are needed from my side.

Regards,
Naman