Re: system generating an NMI due to 80696f991424d ("PCI: pciehp: Tolerate Presence Detect hardwired to zero")

[Oliver Neukum <oneukum@suse.com>]

Am Donnerstag, den 16.01.2020, 06:35 +0100 schrieb Lukas Wunner:
> [cc += Stuart]
> 
> On Wed, Jan 15, 2020 at 12:24:29PM +0100, Lukas Wunner wrote:
> > On Wed, Jan 15, 2020 at 11:26:26AM +0100, Oliver Neukum wrote:
> > > I got a bug report about some systems generating an NMI and
> > > subsequently crashing bisected down to 80696f991424d.
> > > Apparently these systems do not react well to __pciehp_enable_slot
> > > while no card is present. Restoring the check to __pciehp_enable_slot()
> > > removed in 80696f991424d makes the current kernels work.
> > 
> > That's odd, these systems must be setting the Data Link Layer Link Active
> > bit in the Link Status Register even though no card is present.
> 
> Recent PCIe versions allow turning off in-band presence detect, in which
> case the DLLLA bit can be set even though Presence Detect is not set.
> You may be dealing with one of those systems but without full dmesg
> and lspci output this is just an educated guess.
> 
> A series was submitted by Dell last year to support disabling in-band
> presence detect, but it hasn't been merged yet by Bjorn:
> 
> https://lore.kernel.org/linux-pci/20191025190047.38130-1-stuart.w.hayes@gmail.com/
> 
> You may want to try if that series helps.

Hi,

it has been tested and it does the job. May I ask whether you could
ack it or propose necessary changes, so that we can proceed?

	Regards
		Oliver