Re: [RFC/PATCH] Kdump: Disabling PCI interrupts in capture kernel

[Vivek Goyal <vgoyal@in.ibm.com>]

Quoting Grant Grundler <grundler@parisc-linux.org>:

> On Mon, Jun 06, 2005 at 11:07:17PM -0400, Vivek Goyal wrote:
> >   So even if interrupts are disabled on PCI-PCI bridge, interrupts
> generated
> >   by PCI devices on secondary bus are not blocked and I hope device
> should
> >   be working fine.
> 
> How did you plan on disabling interrupts?
> Did you see the MSI discussion that going on now in linux-pci mailing list?

I am following the discussion now. Thanks. 

I am planning to disable only leagacy shared interrupts (irq pin assertion/INTx
emulation) because shared interrupts are a problem. MSI are
not shared but I am not sure can they lead to any other problem.

> 
> > But at the same time kdump kernels are not supposed to
> > do a great deal except capture and save the dump.
> 
> I'd think you want to stop DMA for all devices.
> Just to prevent them from messing more with memory
> that you want to dump - ie get a consistent snapshot.
> Leaving VGA devices alone should be safe.
> 

May be at some point of time. 

> > Disabling interrupts at PCI level should increase the reliability of
> capturing
> > the dump on newer machines with hardware compliant with PCI 2.3 or higher.
> 
> 
> *lots* of PCI devices predate PCI2.3. Possibly even the majority.


Ya, Some other solution is needed for hardware predating PCI2.3. May be Eric's
suggestion of polling the hardware.

Thanks
Vivek