From: Dave Young [mailto:[email protected]] Sent: Monday, August 25, 2014 2:07 PM To: Matt Fleming Cc: Zheng, Lv; Fleming, Matt; linux-efi(a)vger.kernel.org; linux-acpi(a)vger.kernel.org; linux-kernel(a)vger.kernel.org; devel(a)acpica.org; lenb(a)kernel.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: > 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(a)intel.com&gt; > > > 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.