RE: kernel boot fail with efi earlyprintk (bisected)

Hi,

From: Dave Young [mailto:dyoung-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org]
Sent: Monday, August 25, 2014 2:07 PM
To: Matt Fleming
Cc: Zheng, Lv; Fleming, Matt; linux-efi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org; linux-acpi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org; linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org; devel-E0kO6a4B6psdnm+yROfE0A@public.gmane.org;
lenb-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org; Wysocki, Rafael J; Moore, Robert
Subject: Re: kernel boot fail with efi earlyprintk (bisected)

On 08/22/14 at 06:02pm, Dave Young wrote:

quoted

On 08/21/14 at 09:52pm, Matt Fleming wrote:

quoted

On Tue, 19 Aug, at 04:16:58PM, Dave Young wrote:

quoted

Hi,

3.16 kernel boot fail with earlyprintk=efi on my laptop.
It keeps scrolling at the bottom line of screen.

Bisected, the first bad commit is below:
commit 86dfc6f339886559d80ee0d4bd20fe5ee90450f0
Author: Lv Zheng [off-list ref]
Date:   Fri Apr 4 12:38:57 2014 +0800

    ACPICA: Tables: Fix table checksums verification before installation.


I did some debugging by enabling both serial and efi earlyprintk, below is
some debug dmesg, seems early_ioremap fails in scroll up function due to
no free slot, but I'm still not sure if the debug info is right or not.

Thanks Dave, your callstack seems to make sense.

Can you also enable early_ioremap_debug so that we can figure out where
all the FIXMAP slots are going?

With early_ioremap_debug enabled, there will be a lot of "dropped printk", so
I can not get any useful information.

Will try to do more debug.

early_ioremap_debug does not work because we are debugging early_printk but
early_ioremap_debug itself will print warning message at the same time.

Tried what Lv mentioned, increasing the early ioremap slots does help.

Could you send a tested patch to linux-acpi-u79uwXL29TY6noJ6QQ2T4w@public.gmane.org for this?
I think the number of early mapping slots need to be increased by 1 because of this case.

Thanks and best regards
-Lv