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

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

On 7/22/2026 6:45 PM, Thomas Gleixner wrote:
> 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
> 

Understood. Thanks.

Regards,
Naman