On Thu, Jul 30, 2026 at 04:56:27PM +0530, Naman Jain wrote: > > > On 7/28/2026 7:34 PM, [email protected] wrote: > > Thank you for your contribution! Sashiko AI review found 1 potential > > issue(s) to consider: > > > > Pre-existing issues: > > - [High] The fix for dropped pending interrupts during CPU hot-unplug was > > missed in the sister Hyper-V root partition MSI domain. > > -- > > > > --- Patch [1]: [PATCH 1/3] PCI: hv: Set irq_retrigger callback for the > > Hyper-V PCI MSI irqchip --- > > commit b8b1c843c457dd145f0d360b44f4b1bf34bd8cf5 > > Author: Naman Jain <[email protected]> > > > > PCI: hv: Set irq_retrigger callback for the Hyper-V PCI MSI irqchip > > > > 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. 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. > > > > 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]> > > Signed-off-by: Naman Jain <[email protected]> > > > > > 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; > > > > [Severity: High] > > This isn't a bug introduced by this patch, but does the sister Hyper-V root > > partition MSI domain in arch/x86/hyperv/irqdomain.c also need this fix? > > > > Looking at hv_init_dev_msi_info(), it appears to be missing the exact same > > callback initialization for the root partition's top-level irq_chip: > > > > arch/x86/hyperv/irqdomain.c:hv_init_dev_msi_info() { > > ... > > if (!msi_lib_init_dev_msi_info(dev, domain, real_parent, info)) > > return false; > > > > chip->flags |= IRQCHIP_SKIP_SET_WAKE | IRQCHIP_MOVE_DEFERRED; > > > > info->ops->msi_prepare = pci_msi_prepare; > > > > return true; > > } > > > > If a CPU is hot-unplugged while a device MSI interrupt is pending in its > > local APIC IRR, could fixup_irqs() fail to resend the pending interrupt > > to the new target CPU because this callback is NULL? > > > > This could potentially lead to the same lost interrupts and I/O stalls > > described in this commit message, just in the root partition MSI domain > > instead of the guest paravirtual MSI domain. > > > > > if (IS_ENABLED(CONFIG_X86)) > > > chip->flags |= IRQCHIP_MOVE_DEFERRED; > > > > > > > I am not planning to include this in this series, since this issue is not > seen in root partition yet and I am not sure if it is applicable here. > Second patch would anyways fix it going forward, but I am OK adding the > change for this, if we need.
What's the downside of fixing the root partition irq domain? We never really attempted to unplug any CPU from the root partition, so it is unsurprising that it has not been reported. Wei > > Regards, > Naman >
