Re: [RFC PATCH] x86/apic: Fix lost IRQ during forced vector migration on Hyper-V

[Thomas Gleixner <tglx@kernel.org>]

Naman!

On Wed, Jul 22 2026 at 14:59, Naman Jain wrote:
> I completely agree with your comments, and now that I know how to fix 
> this, do you suggest me to -
>
> 1. add irq_retrigger callback in pci-hyperv.c
> or
> 2. go with your fixup-irq() change to no longer need drivers to add the 
> above? And then see what all stale irq_retrigger inits can be removed
>
> Going with 1) would be easier for me to fix this bug, and back port it 
> to older kernels, with proper Fixes tag (pointing to some pci-hyperv.c 
> change).
> Then later, we can go with 2) separately as a general enhancement (not a 
> Fix).

This should be one patch series:

  1) Add the callback to pci-hyperv, i.e. in hv_pcie_init_dev_msi_info()

     +    chip->irq_retrigger = irq_chip_retrigger_hierarchy;

     That sets it on the outermost domain interrupt chip (PCI/MSI
     device domain), which is what fixup_irqs() looks at.

     This one needs a Fixes: tag (The first commit which introduced the
     driver) and a Cc: stable@... so it will be backported.

  2) Change fixup_irqs() to use irq_chip_retrigger_hierarchy()

     Feel free to pick up the patch I gave you, add a proper change log
     and a Suggested-by: Thomas .... tag.

  3) Remove the initialization of the outermost chip from arch/x86/* and
     drivers/iommu/amd/* as that's not longer required then.

Thanks,

        tglx