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

[Linus Torvalds]

On Fri, Jan 5, 2018 at 2:04 PM, Aaro Koskinen <aaro.koskinen@xxxxxx> 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 KÃnig <christian.koenig@xxxxxxx>
> 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)?

I wonder why that patch wasn't applied, but if it doesn't fix things,
I think we do need to revert it all.

Christian? Bjorn?

                 Linus
From e5d5c9682aa02a6b9c0c6bd446d433b924441679 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Christian=20K=C3=B6nig?= <christian.koenig@xxxxxxx>
Date: Tue, 28 Nov 2017 10:02:35 +0100
Subject: [PATCH 3/3] x86/PCI: limit the size of the 64bit BAR to 256GB
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

This avoids problems with Xen which hides some memory resources from the
OS and potentially also allows memory hotplug while this fixup is
enabled.

Signed-off-by: Christian KÃnig <christian.koenig@xxxxxxx>
---
 arch/x86/pci/fixup.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/pci/fixup.c b/arch/x86/pci/fixup.c
index c817ab85dc82..149adbc7f2a3 100644
--- a/arch/x86/pci/fixup.c
+++ b/arch/x86/pci/fixup.c
@@ -701,7 +701,7 @@ static void pci_amd_enable_64bit_bar(struct pci_dev *dev)
 	res->name = "PCI Bus 0000:00";
 	res->flags = IORESOURCE_PREFETCH | IORESOURCE_MEM |
 		IORESOURCE_MEM_64 | IORESOURCE_WINDOW;
-	res->start = 0x100000000ull;
+	res->start = 0xbd00000000ull;
 	res->end = 0xfd00000000ull - 1;
 
 	/* Just grab the free area behind system memory for this */
-- 
2.11.0