linux-kernel - [PATCH v3 0/2] x86, espfix: silence warning on espfix initialization for ap

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Date:	Fri, 3 Jul 2015 17:37:17 +0800
From:	Zhu Guihua <zhugh.fnst@...fujitsu.com>
To:	<linux-kernel@...r.kernel.org>
CC:	<mingo@...nel.org>, <hpa@...or.com>, <luto@...capital.net>,
	<luto@...nel.org>, <bp@...en8.de>, <tglx@...utronix.de>,
	<x86@...nel.org>, Zhu Guihua <zhugh.fnst@...fujitsu.com>
Subject: [PATCH v3 0/2] x86, espfix: silence warning on espfix initialization for ap

The following lockdep warning occurrs when running with latest kernel:
[    3.178000] ------------[ cut here ]------------
[    3.183000] WARNING: CPU: 128 PID: 0 at kernel/locking/lockdep.c:2755 lockdep_trace_alloc+0xdd/0xe0()
[    3.193000] DEBUG_LOCKS_WARN_ON(irqs_disabled_flags(flags))
[    3.199000] Modules linked in:

[    3.203000] CPU: 128 PID: 0 Comm: swapper/128 Not tainted 4.1.0-rc3 #70
[    3.221000]  0000000000000000 2d6601fb3e6d4e4c ffff88086fd5fc38 ffffffff81773f0a
[    3.230000]  0000000000000000 ffff88086fd5fc90 ffff88086fd5fc78 ffffffff8108c85a
[    3.238000]  ffff88086fd60000 0000000000000092 ffff88086fd60000 00000000000000d0
[    3.246000] Call Trace:
[    3.249000]  [<ffffffff81773f0a>] dump_stack+0x4c/0x65
[    3.255000]  [<ffffffff8108c85a>] warn_slowpath_common+0x8a/0xc0
[    3.261000]  [<ffffffff8108c8e5>] warn_slowpath_fmt+0x55/0x70
[    3.268000]  [<ffffffff810ee24d>] lockdep_trace_alloc+0xdd/0xe0
[    3.274000]  [<ffffffff811cda0d>] __alloc_pages_nodemask+0xad/0xca0
[    3.281000]  [<ffffffff810ec7ad>] ? __lock_acquire+0xf6d/0x1560
[    3.288000]  [<ffffffff81219c8a>] alloc_page_interleave+0x3a/0x90
[    3.295000]  [<ffffffff8121b32d>] alloc_pages_current+0x17d/0x1a0
[    3.301000]  [<ffffffff811c869e>] ? __get_free_pages+0xe/0x50
[    3.308000]  [<ffffffff811c869e>] __get_free_pages+0xe/0x50
[    3.314000]  [<ffffffff8102640b>] init_espfix_ap+0x17b/0x320
[    3.320000]  [<ffffffff8105c691>] start_secondary+0xf1/0x1f0
[    3.327000] ---[ end trace 1b3327d9d6a1d62c ]---

As we alloc pages with GFP_KERNEL in init_espfix_ap() which is called
before enabled local irq, and the lockdep sub-system considers this
behaviour as allocating memory with GFP_FS with local irq disabled,
then trigger the warning as mentioned about.

So we allocate them on the boot CPU side when the target CPU is bringing
up by the primary CPU, and hand them over to the secondary CPU.

v3:
 -split the original path into two parts

v2:
 -allocate espfix stack pages when the targert CPU is bringing up by the
  primary CPU
 -commit messages changed

v1:
 -Alloc the page on the node the target CPU is on.

Zhu Guihua (2):
  espfix: add cpu parameter to init_espfix_ap()
  x86, espfix: init espfix on the boot cpu side

 arch/x86/include/asm/espfix.h |  2 +-
 arch/x86/kernel/espfix_64.c   | 28 ++++++++++++++++------------
 arch/x86/kernel/smpboot.c     | 14 +++++++-------
 3 files changed, 24 insertions(+), 20 deletions(-)

-- 
1.9.3

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