linux-kernel - [PATCH v13 0/4] x86/earlyprintk: setup serial earlyprintk as early as possible

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Date:	Sat, 27 Jun 2015 19:45:39 +0600
From:	Alexander Kuleshov <kuleshovmail@...il.com>
To:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	Borislav Petkov <bp@...e.de>,
	David Cohen <david.a.cohen@...ux.intel.com>
Cc:	linux-kernel@...r.kernel.org,
	Alexander Kuleshov <kuleshovmail@...il.com>
Subject: [PATCH v13 0/4] x86/earlyprintk: setup serial earlyprintk as early as possible

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
means that earlyprintk will be usable only after the 'parse_early_param'
will be executed or in another words earlyprintk is usable only during early
boot, kernel decompression and after call of the parse_early_param. But
there are many stuff after the kernel decompression and before the
parse_early_param will be called as memblock usage, early cpu initialization,
early ioremap initialization and etc... So earlyprintk allows us to see
what's going on there.

Changelog:

v13:
  * do not setup pciserial from the arch/x86/kernel/head{32,64}.c, because
it uses ioremap and we can't do it really early;
  * style fixes;
  * patch for testing.

v12:
  * all changes from the v11 are reverted
  * setup_early_serial_console renamed to the setup_earlyprintk_console and
refactored. Now it checks 'earlyprintk=' in the kernel command line, set
earlyprintk_late variable to false. This variable allows to know, do we
can setup early console for the certain device.

v11:
  * setup_log_buf moved to the arch/x86/kernel/head{32,64.c} from
the arch/x86/kernel/setup.c to setup early log_buf for the earlyprintl
  * Update log_buf in the early_printk function
  * Added additional patch for testing earlyprintk

v10:
  * Removed style issues which are not related to the patchset.

v9:
  * Add call of the lockdep_init to the arch/x86/kernel/head{32,64}.c
before the serial console initialization to prevent:

[ 0.000000] WARNING: lockdep init error! lock-(console_sem).lock was acquiredbefore lockdep_init
[ 0.000000] Call stack leading to lockdep invocation was:
[ 0.000000] [] save_stack_trace+0x2f/0x50
[ 0.000000] [] __lock_acquire+0xa2c/0xf00
[ 0.000000] [] lock_acquire+0xdb/0x2b0
[ 0.000000] [] _raw_spin_lock_irqsave+0x53/0x90
[ 0.000000] [] down+0x16/0x50
[ 0.000000] [] console_lock+0x19/0x60
[ 0.000000] [] register_console+0x116/0x350
[ 0.000000] [] setup_early_printk+0x165/0x467
[ 0.000000] [] setup_early_serial_console+0x56/0x58
[ 0.000000] [] x86_64_start_kernel+0xce/0x110
[ 0.000000] [] 0xffffffffffffffff
[ 0.000000] ------------------------

during early serial console initialization.

  * Add additional check to the earlyprintk initialization to protect double initialization
of the early_serial_console.
  * Fixed comment.

v8:
  * Fixed warning with the definition of the setup_early_serial_console in the
arch/x86/include/asm/setup.h

v7:
  * Move setup_early_serial_console to the the arch/x86/include/setup.h
  * Add ifdefs to prevent setup_serial_console if CONFIG_EARLY_PRINTK is not set.

v6:
  * Style fixes.
  * Call of the suetp_builtin_cmdline moved to the separate patch.

v5:
  * Call setup_builtin_cmdline instead of setup_cmdline

v4:
  * Move setup_early_serial_console from the include/linux/printk.h to the
arch/x86/include/asm/serial.h, because this function is only for x86 now.

v3:
  * Call setup_cmdline before setup_early_printk;
  * setup_early_printk call wrapped with the setup_early_serial_console which
checks that 'serial' given to the earlyprintk command line option. This prevents
call of the setup_early_printk with the given pciserial/dbgp/efi, because they
are using early_ioremap.

v2:
  * Comment added before the setup_early_printk call;
  * Added information about testing to the commit message.

Alexander Kuleshov (4):
  x86/setup: introduce setup_bultin_cmdline
  x86/setup: handle builtin command line as early as possible
  x86/earlyprintk: setup earlyprintk as early as possible
  x86/earlyprintk: add some early_printk for tests

 arch/x86/include/asm/setup.h   |  8 +++++++-
 arch/x86/kernel/early_printk.c | 42 +++++++++++++++++++++++++++++++++++-------
 arch/x86/kernel/head32.c       |  9 +++++++++
 arch/x86/kernel/head64.c       |  8 ++++++++
 arch/x86/kernel/setup.c        | 30 +++++++++++++++++-------------
 init/main.c                    |  2 ++
 6 files changed, 78 insertions(+), 21 deletions(-)

--
2.4.4.410.gc71d752

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