Comment 0 for bug 1797990
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| Guilherme G. Piccoli (gpiccoli) wrote | #0 |
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We have reports of a kdump failure in Ubuntu (in x86 machine) that was narrowed down to a MSI irq storm coming from a PCI network device.
The bug manifests as a lack of progress in the boot process of the kdump kernel, and a storm of kernel messages like:
[...]
[ 342.265294] do_IRQ: 0.155 No irq handler for vector
[ 342.266916] do_IRQ: 0.155 No irq handler for vector
[ 347.258422] do_IRQ: 14053260 callbacks suppressed
[...]
The root cause of the the issue is that the kdump kernel kexec process does not ensure PCI devices are reset and/or MSI capabilities are disabled, so a PCI device could produce a huge amount of PCI irqs which would take all the processing time for the CPU (specially since we restrict the kdump kernel to use one single CPU only).
This was tested using upstream kernel version 4.18, and the problem reproduces.
In the specific test scenario, the PCI NIC was an "Intel 82599ES 10-Gigabit [8086:10fb]" that was used in SR-IOV PCI passthrough mode (vfio_pci), under high load on the guest.