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Date: Mon, 8 Jun 2015 11:33:26 +0200
From: Borislav Petkov <bp@...e.de>
To: Alexander Kuleshov <kuleshovmail@...il.com>
Cc: Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>,
"H. Peter Anvin" <hpa@...or.com>,
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
LKML <linux-kernel@...r.kernel.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Mark Rustad <mark.d.rustad@...el.com>,
Yinghai Lu <yinghai@...nel.org>
Subject: Re: [PATCH v10 3/3] x86/earlyprintk: setup earlyprintk as early as
possible
On Sun, Jun 07, 2015 at 08:14:37PM +0600, Alexander Kuleshov wrote:
> The early_printk function is usable only after the setup_early_printk will
> be executed. We pass 'earlyprintk' through the kernel command line, so it
> will be usable only after the 'parse_early_param' will be executed. This means
> that we have usable earlyprintk only during early boot, kernel decompression
> and after call of the 'parse_early_param'. This patchset makes earlyprintk
> usable before the call of the 'parse_early_param'.
>
> This patch makes the setup_early_printk visible for head{32,64}.c. So the
> 'early_printk' function will be usabable after decompression of the
> kernel and before parse_early_param will be called. It also must be
> safe if CONFIG_CMDLINE_BOOL and CONFIG_CMDLINE_OVERRIDE are set, because
> setup_cmdline function will be called before setup_early_printk.
>
> It provides earlyprintk only for serial console, because other needs in
> ioremap which is not initialized yet.
>
> Tested it with qemu, so early_printk() is usable and prints to serial
> console right after setup_early_printk function called.
>
> Signed-off-by: Alexander Kuleshov <kuleshovmail@...il.com>
> ---
> arch/x86/include/asm/setup.h | 7 +++++++
> arch/x86/kernel/early_printk.c | 30 ++++++++++++++++++++++++++++--
> arch/x86/kernel/head32.c | 7 +++++++
> arch/x86/kernel/head64.c | 6 ++++++
> 4 files changed, 48 insertions(+), 2 deletions(-)
...
> diff --git a/arch/x86/kernel/head32.c b/arch/x86/kernel/head32.c
> index 92e8b5f..6969d97 100644
> --- a/arch/x86/kernel/head32.c
> +++ b/arch/x86/kernel/head32.c
> @@ -32,6 +32,13 @@ static void __init i386_default_early_setup(void)
> asmlinkage __visible void __init i386_start_kernel(void)
> {
> setup_builtin_cmdline();
> +
> + lockdep_init();
> +
> + setup_early_serial_console();
> +
> + early_printk("Early printk is initialized\n");
> +
> cr4_init_shadow();
> sanitize_boot_params(&boot_params);
>
> diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
> index 1e5f064..769d411 100644
> --- a/arch/x86/kernel/head64.c
> +++ b/arch/x86/kernel/head64.c
> @@ -174,7 +174,12 @@ asmlinkage __visible void __init x86_64_start_kernel(char * real_mode_data)
>
> setup_builtin_cmdline();
>
> + lockdep_init();
So you've added that lockdep_init() call here and above on the 32-bit
path and haven't removed the one in start_kernel().
* Then, your patches don't apply. Something garbles them insanely so that
not even fuzzy, ignore-context patch --merge works. Please fix your
setup. For that, send your patches to yourself and try applying them.
Send them out only if they apply cleanly.
And do them against tip/master or latest Linus rc, alternatively.
* To that patchset: I did the diff below ontop of yours to check whether
that early printk actually works.
And it doesn't on my test box here.
The beginning of my dmesg contains:
[ 0.000000] bootconsole [earlyser0] enabled
[ 0.000000] Initializing cgroup subsys cpuset
[ 0.000000] Initializing cgroup subsys cpu
[ 0.000000] Initializing cgroup subsys cpuacct
[ 0.000000] Linux version 4.1.0-rc6+ (root@...dor) (gcc version 4.9.1 (Debian 4.9.1-19) ) #2 SMP PREEMPT Mon Jun 8 11:10:00 CEST 2015
[ 0.000000] Command line: BOOT_IMAGE=/boot/vmlinuz-4.1.0-rc6+ root=/dev/sda7 ro earlyprintk=ttyS0,115200 console=ttyS0,115200 console=tty0 root=/dev/sda7 log_buf_len=10M resume=/dev/sda5 no_console_suspend ignore_loglevel
[ 0.000000] KERNEL supported cpus:
[ 0.000000] Intel GenuineIntel
[ 0.000000] AMD AuthenticAMD
[ 0.000000] Centaur CentaurHauls
[ 0.000000] x86/fpu: xstate_offset[2]: 0240, xstate_sizes[2]: 0100
[ 0.000000] x86/fpu: Supporting XSAVE feature 0x01: 'x87 floating point registers'
[ 0.000000] x86/fpu: Supporting XSAVE feature 0x02: 'SSE registers'
[ 0.000000] x86/fpu: Supporting XSAVE feature 0x04: 'AVX registers'
[ 0.000000] x86/fpu: Enabled xstate features 0x7, context size is 0x340 bytes, using 'standard' format.
[ 0.000000] x86/fpu: Using 'eager' FPU context switches.
[ 0.000000] e820: BIOS-provided physical RAM map:
...
and I have CONFIG_EARLY_PRINTK=y. So provided I'm not missing anything,
I'd say you'd need to do more staring.
So I'd suggest you test your patches on bare metal, both 32-bit and
64-bit with a similar diff as the one I've done below.
HTH.
---
diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
index d4ea6ec28f09..20dd514ce838 100644
--- a/arch/x86/kernel/head64.c
+++ b/arch/x86/kernel/head64.c
@@ -179,7 +179,6 @@ asmlinkage __visible void __init x86_64_start_kernel(char * real_mode_data)
early_printk("Early printk is initialized\n");
-
/*
* Load microcode early on BSP.
*/
@@ -202,5 +201,7 @@ void __init x86_64_start_reservations(char *real_mode_data)
reserve_ebda_region();
+ early_printk("Will start_kernel\n");
+
start_kernel();
}
diff --git a/init/main.c b/init/main.c
index 2115055faeac..e9180445283e 100644
--- a/init/main.c
+++ b/init/main.c
@@ -494,6 +494,8 @@ asmlinkage __visible void __init start_kernel(void)
char *command_line;
char *after_dashes;
+ early_printk("Will run lockdep_init needlessly one more time\n");
+
/*
* Need to run as early as possible, to initialize the
* lockdep hash:
@@ -530,6 +532,8 @@ asmlinkage __visible void __init start_kernel(void)
build_all_zonelists(NULL, NULL);
page_alloc_init();
+ early_printk("Early Kernel command line: %s\n", boot_command_line);
+
pr_notice("Kernel command line: %s\n", boot_command_line);
parse_early_param();
after_dashes = parse_args("Booting kernel",
--
Regards/Gruss,
Boris.
ECO tip #101: Trim your mails when you reply.
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