Re: [PATCH v3 3/3] x86/irq, iommu/amd, x86/hyperv, PCI: Drop redundant irq_retrigger inits

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

On 9/8/2026 1:24 AM, Michael Kelley wrote:
> From: Naman Jain <namjain@linux.microsoft.com> Sent: Sunday, September 6, 2026 11:51 PM
>>
>> With fixup_irqs() and the generic resend path (try_retrigger()) now both
>> falling back to irq_chip_retrigger_hierarchy(), installing it as the
>> irq_retrigger() callback on the outermost domain chips is no longer
>> required. The hierarchy walk reaches the x86 vector domain's
>> apic_retrigger_irq() for all of these stacked domain chips.
>>
>> Remove the now redundant irq_retrigger() initializations from the outermost
>> domain interrupt chips, including the Hyper-V root partition PCI/MSI chip.
>> msi_set_affinity() is the only site that invoked the outermost chip's
>> irq_retrigger() directly. Convert it to irq_chip_retrigger_hierarchy() so
>> the x86_init_dev_msi_info() initialization can be dropped as well.
>>
>> No functional change intended.
>>
>> Suggested-by: Thomas Gleixner <tglx@kernel.org>
>> Reviewed-by: Shradha Gupta <shradhagupta@linux.microsoft.com>
>> Signed-off-by: Naman Jain <namjain@linux.microsoft.com>
>> ---
>>   arch/x86/hyperv/irqdomain.c         | 1 -
>>   arch/x86/kernel/apic/io_apic.c      | 2 --
>>   arch/x86/kernel/apic/msi.c          | 4 +---
>>   arch/x86/kernel/hpet.c              | 1 -
>>   drivers/iommu/amd/init.c            | 1 -
>>   drivers/pci/controller/pci-hyperv.c | 1 -
>>   6 files changed, 1 insertion(+), 9 deletions(-)
>>
> 
> [snip]
> 
>> diff --git a/arch/x86/kernel/apic/msi.c b/arch/x86/kernel/apic/msi.c
>> index 66bc5d3e79db3..aad2f15eb2176 100644
>> --- a/arch/x86/kernel/apic/msi.c
>> +++ b/arch/x86/kernel/apic/msi.c
>> @@ -137,7 +137,7 @@ msi_set_affinity(struct irq_data *irqd, const struct cpumask *mask, bool force)
>>   	 * IRR.
>>   	 */
>>   	if (lapic_vector_set_in_irr(cfg->vector))
>> -		irq_data_get_irq_chip(irqd)->irq_retrigger(irqd);
>> +		irq_chip_retrigger_hierarchy(irqd);
> 
> In v2 of this patch series, I commented about whether this code
> should also check for irq_retrigger() being set in the outermost
> domain before calling irq_chip_retrigger_hierarchy(). fixup_irqs()
> in Patch 2 of this series has that check, and I think it should be
> here as well. While there are no domains in the x86 world today
> that have a custom irq_retrigger function, I'll argue the check
> should be done so the infrastructure is correct if such a domain
> were added in the future.
> 
> Michael
> 

The reason I skipped changing this is because I realized that unlike
fixup_irqs(), this path is not generic, i.e. the chip you get here is
the same one as the one initialized in x86_init_dev_msi_info() below. So
someone adding a custom irq_retrigger function could simply change it in
above call site.
However, on looking at this again, I see if someone adds this custom
function again, it would be taken care of in fixup_irqs() but
msi_set_affinity() could silently be missed. I'll add the fallback soon
in next version.

Regards,
Naman

>>
>>   	return ret;
>>   }
>> @@ -246,7 +246,6 @@ static bool x86_init_dev_msi_info(struct device *dev, struct irq_domain *domain,
>>   	info->ops->msi_prepare		= x86_msi_prepare;
>>
>>   	info->chip->irq_ack		= irq_chip_ack_parent;
>> -	info->chip->irq_retrigger	= irq_chip_retrigger_hierarchy;
>>   	info->chip->flags		|= IRQCHIP_SKIP_SET_WAKE |
>>   					   IRQCHIP_AFFINITY_PRE_STARTUP;
>>
>> @@ -313,7 +312,6 @@ static struct irq_chip dmar_msi_controller = {
>>   	.irq_mask		= dmar_msi_mask,
>>   	.irq_ack		= irq_chip_ack_parent,
>>   	.irq_set_affinity	= msi_domain_set_affinity,
>> -	.irq_retrigger		= irq_chip_retrigger_hierarchy,
>>   	.irq_compose_msi_msg	= dmar_msi_compose_msg,
>>   	.irq_write_msi_msg	= dmar_msi_write_msg,
>>   	.flags			= IRQCHIP_SKIP_SET_WAKE |  IRQCHIP_MOVE_DEFERRED |
>> diff --git a/arch/x86/kernel/hpet.c b/arch/x86/kernel/hpet.c
>> index 8dc7b710e1250..2bb7a6f466af3 100644
>> --- a/arch/x86/kernel/hpet.c
>> +++ b/arch/x86/kernel/hpet.c
>> @@ -509,7 +509,6 @@ static struct irq_chip hpet_msi_controller __ro_after_init = {
>>   	.irq_mask = hpet_msi_mask,
>>   	.irq_ack = irq_chip_ack_parent,
>>   	.irq_set_affinity = msi_domain_set_affinity,
>> -	.irq_retrigger = irq_chip_retrigger_hierarchy,
>>   	.irq_write_msi_msg = hpet_msi_write_msg,
>>   	.flags = IRQCHIP_SKIP_SET_WAKE | IRQCHIP_AFFINITY_PRE_STARTUP,
>>   };
>> diff --git a/drivers/iommu/amd/init.c b/drivers/iommu/amd/init.c
>> index 40726dfef2733..a19e1faf98750 100644
>> --- a/drivers/iommu/amd/init.c
>> +++ b/drivers/iommu/amd/init.c
>> @@ -2471,7 +2471,6 @@ static struct irq_chip intcapxt_controller = {
>>   	.irq_unmask		= intcapxt_unmask_irq,
>>   	.irq_mask		= intcapxt_mask_irq,
>>   	.irq_ack		= irq_chip_ack_parent,
>> -	.irq_retrigger		= irq_chip_retrigger_hierarchy,
>>   	.irq_set_affinity       = intcapxt_set_affinity,
>>   	.irq_set_wake		= intcapxt_set_wake,
>>   	.flags			= IRQCHIP_MASK_ON_SUSPEND |
>> IRQCHIP_MOVE_DEFERRED,
>> diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
>> index 89816a2bd7cd3..cfc8fa403dad6 100644
>> --- a/drivers/pci/controller/pci-hyperv.c
>> +++ b/drivers/pci/controller/pci-hyperv.c
>> @@ -2119,7 +2119,6 @@ static bool hv_pcie_init_dev_msi_info(struct device *dev,
>> struct irq_domain *dom
>>   	info->ops->msi_prepare = hv_msi_prepare;
>>
>>   	chip->irq_set_affinity = irq_chip_set_affinity_parent;
>> -	chip->irq_retrigger = irq_chip_retrigger_hierarchy;
>>
>>   	if (IS_ENABLED(CONFIG_X86))
>>   		chip->flags |= IRQCHIP_MOVE_DEFERRED;
>> --
>> 2.43.0
>>
>