[Regression] kdump fails to get DHCP address unless booting with pci=nomsi or without nr_cpus=1

[Thomas Gleixner]

On Mon, Aug 11 2025 at 15:02, Thomas Gleixner wrote:

CC+ Marc

> On Mon, Aug 11 2025 at 11:23, Coiby Xu wrote:
>> Recently I met an issue that on certain virtual machines, the kdump
>> kernel fails to get DHCP IP address most of times starting from
>> 6.11-rc2. git bisection shows commit b5712bf89b4b ("irqchip/gic-v3-its:
>> Provide MSI parent for PCI/MSI[-X]") is the 1st bad commit,
>>
>>      # good: [7d189c77106ed6df09829f7a419e35ada67b2bd0] PCI/MSI: Provide
>>      # MSI_FLAG_PCI_MSI_MASK_PARENT
>>      git bisect good 7d189c77106ed6df09829f7a419e35ada67b2bd0
>>      # good: [48f71d56e2b87839052d2a2ec32fc97a79c3e264] irqchip/gic-v3-its:
>>      # Provide MSI parent infrastructure
>>      git bisect good 48f71d56e2b87839052d2a2ec32fc97a79c3e264
>>      # good: [8c41ccec839c622b2d1be769a95405e4e9a4cb20] irqchip/irq-msi-lib:
>>      # Prepare for PCI MSI/MSIX
>>      git bisect good 8c41ccec839c622b2d1be769a95405e4e9a4cb20
>>      # first bad commit: [b5712bf89b4bbc5bcc9ebde8753ad222f1f68296]
>>      # irqchip/gic-v3-its: Provide MSI parent for PCI/MSI[-X]
>
> There were follow up fixes on this, so isolating this one is not really
> conclusive.
>
> Is the problem still there on v6.16 and v6.17-rc1?
>
> Thanks,
>
>         tglx