On Mon, Aug 24, 2026 at 11:57:56AM +0530, Naman Jain wrote: > > > On 8/24/2026 5:44 AM, Wei Liu wrote: > > 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? > > No downside as such. It would be a latent bug, exposed only if we exercise > hotplug in root partition, which seems like we don't. After patch 2 of this > series, that would go away anyways. If you tell me, I can add a change > similar to patch 1, which is backportable, but then I would need to remove > it similarly in patch 3.
Yes, please fix that for the root partition, too. Being consistent across different use cases is going to save us some headache in the future. Wei
