linux-kernel - Re: [BISECTED] v4.15-rc: Boot regression on x86

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Message-ID: <20180106120211.gibjmzrbi5hcpexj@darkstar.musicnaut.iki.fi>
Date:   Sat, 6 Jan 2018 14:02:11 +0200
From:   Aaro Koskinen <aaro.koskinen@....fi>
To:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Christian König <christian.koenig@....com>
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [BISECTED] v4.15-rc: Boot regression on x86_64/AMD

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@....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@....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.

A.