Re: [PATCH 1/3] x86/quirks: Scan all busses for early PCI quirks

[Bjorn Helgaas]

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.