From: Naman Jain <[email protected]> Sent: Monday, August 10, 2026 2:07 AM > > The Hyper-V vPCI MSI irqchip never installs an irq_retrigger() callback. > > On CPU hot-unplug fixup_irqs() migrates the interrupts which are affine to > the outgoing CPU to a new target. If an interrupt still has its pending bit > set in the outgoing CPU's IRR at that point, fixup_irqs() resends it on the > new target through the irqchip's irq_retrigger() callback. As the Hyper-V > PCI/MSI chip does not provide that callback, the pending interrupt is > silently dropped, which can result in lost interrupts, stalls and "No irq > handler for vector" messages during CPU hotplug. > > Install irq_chip_retrigger_hierarchy() as the irq_retrigger() callback for > the Hyper-V PCI/MSI irqchip, so that a pending interrupt is resent on its > new target CPU via the parent x86 vector domain. > > Fixes: 4daace0d8ce85 ("PCI: hv: Add paravirtual PCI front-end for Microsoft > Hyper-V VMs") > Cc: [email protected] > Suggested-by: Long Li <[email protected]> > Suggested-by: Thomas Gleixner <[email protected]> > Reviewed-by: Aditya Garg <[email protected]> > Reviewed-by: Shradha Gupta <[email protected]> > Signed-off-by: Naman Jain <[email protected]> > --- > drivers/pci/controller/pci-hyperv.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/drivers/pci/controller/pci-hyperv.c > b/drivers/pci/controller/pci-hyperv.c > index cfc8fa403dad6..89816a2bd7cd3 100644 > --- a/drivers/pci/controller/pci-hyperv.c > +++ b/drivers/pci/controller/pci-hyperv.c > @@ -2119,6 +2119,7 @@ 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 >
Reviewed-by: Michael Kelley <[email protected]>
