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SubjectRe: [PATCH 1/3] x86/quirks: Scan all busses for early PCI quirks
On Sat, Nov 14, 2020 at 12:40:10AM +0100, Thomas Gleixner wrote:
> Bjorn,
>
> On Sat, Nov 14 2020 at 00:31, Thomas Gleixner wrote:
> > On Fri, Nov 13 2020 at 10:46, Bjorn Helgaas wrote:
> >> pci_device_shutdown() still clears the Bus Master Enable bit if we're
> >> doing a kexec and the device is in D0-D3hot, which should also disable
> >> MSI/MSI-X. Why doesn't this solve the problem? Is this because the
> >> device causing the storm was in PCI_UNKNOWN state?
> >
> > That's indeed a really good question.
>
> So we do that on kexec, but is that true when starting a kdump kernel
> from a kernel crash? I doubt it.

Ah, right, I bet that's it, thanks. The kdump path is basically this:

crash_kexec
machine_kexec

while the usual kexec path is:

kernel_kexec
kernel_restart_prepare
device_shutdown
while (!list_empty(&devices_kset->list))
dev->bus->shutdown
pci_device_shutdown # pci_bus_type.shutdown
machine_kexec

So maybe we need to explore doing some or all of device_shutdown() in
the crash_kexec() path as well as in the kernel_kexec() path.

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