linux-kernel - Re: kernel boot fail with efi earlyprintk (bisected)

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Date:	Mon, 25 Aug 2014 14:07:13 +0800
From:	Dave Young <dyoung@...hat.com>
To:	Matt Fleming <matt@...sole-pimps.org>
Cc:	lv.zheng@...el.com, matt.fleming@...el.com,
	linux-efi@...r.kernel.org, linux-acpi@...r.kernel.org,
	linux-kernel@...r.kernel.org, devel@...ica.org, lenb@...nel.org,
	rafael.j.wysocki@...el.com, robert.moore@...el.com
Subject: Re: kernel boot fail with efi earlyprintk (bisected)

On 08/22/14 at 06:02pm, Dave Young wrote:
> On 08/21/14 at 09:52pm, Matt Fleming wrote:
> > On Tue, 19 Aug, at 04:16:58PM, Dave Young wrote:
> > > 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 <lv.zheng@...el.com>
> > > 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.

Thanks
Dave
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