Re: [BISECTED] v4.15-rc: Boot regression on x86_64/AMD

["Christian König" <christian.koenig@amd.com>]

Am 06.01.2018 um 13:02 schrieb Aaro Koskinen:
> Hi,
>
> On Sat, Jan 06, 2018 at 04:10:38AM +0200, Aaro Koskinen wrote:
>> On Fri, Jan 05, 2018 at 04:00:25PM -0800, Linus Torvalds wrote:
>>> On Fri, Jan 5, 2018 at 2:04 PM, Aaro Koskinen <aaro.koskinen@iki.fi> wrote:
>>>> After v4.14, I've been unable to boot my AMD compilation box with the
>>>> v4.15-rc mainline Linux. It just ends up in a silent reboot loop.
>>>>
>>>> I bisected this to:
>>>>
>>>> commit fa564ad9636651fd11ec2c79c48dee844066f73a
>>>> Author: Christian König <christian.koenig@amd.com>
>>>> Date:   Tue Oct 24 14:40:29 2017 -0500
>>>>
>>>>      x86/PCI: Enable a 64bit BAR on AMD Family 15h (Models 00-1f, 30-3f, 60-7f)
>>> Hmm. That was reported to break boot earlier already.
>>>
>>> The breakage was supposedly fixed by three patches from Christian:
>>>
>>>    a19e2696135e: "x86/PCI: Only enable a 64bit BAR on single-socket AMD
>>> Family 15h"
>>>
>>>    470195f82e4e:  "x86/PCI: Fix infinite loop in search for 64bit BAR placement"
>>>
>>> and a third one that was apparently never applied.
>>>
>>> I'm not sure why that third patch was never applied, I'm including it here.
>>>
>>> Does the system work for you if you apply that patch (instead of
>>> reverting all of them)?
>> Yes, I think it now works.
>>
>> When booting with kexec from v4.14:
>> 89876f275e8d562912d9c238cd888b52065cf25c alone ==> boot fails.
>> 89876f275e8d562912d9c238cd888b52065cf25c and the patch ==> boot OK.
> I also re-tested with normal reboot/reset and BIOS boot (just to eliminate
> any kexec side-effects), and the results are the same. The patch
> "x86/PCI: limit the size of the 64bit BAR to 256GB" is fixing the boot
> on my system.

Ah, crap. We left this one out because it was just a hacky shoot into 
the dark to potentially avoid problems.

Please provide me with a full dmesg of the system and the content of 
/proc/iomem.

The most likely root cause is that your BIOS is buggy and reporting some 
nonsense to the OS.

We either need to indeed limit the new PCI root window to 256GB or find 
a better way to detect problematic BIOS versions.

Thanks in advance,
Christian.

>
> A.