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authorSuresh Siddha <suresh.b.siddha@intel.com>2011-02-02 17:02:55 -0800
committerIngo Molnar <mingo@elte.hu>2011-02-03 12:10:38 +0100
commitf7448548a9f32db38f243ccd4271617758ddfe2c (patch)
tree211ed2986556691559eee8d1f730127c2ce0017d /arch/x86/include
parentf12d3d04e8f6223276abb068c5d72852174b8c31 (diff)
downloadlinux-linaro-android-f7448548a9f32db38f243ccd4271617758ddfe2c.tar.gz
x86, mtrr: Avoid MTRR reprogramming on BP during boot on UP platforms
Markus Kohn ran into a hard hang regression on an acer aspire 1310, when acpi is enabled. git bisect showed the following commit as the bad one that introduced the boot regression. commit d0af9eed5aa91b6b7b5049cae69e5ea956fd85c3 Author: Suresh Siddha <suresh.b.siddha@intel.com> Date: Wed Aug 19 18:05:36 2009 -0700 x86, pat/mtrr: Rendezvous all the cpus for MTRR/PAT init Because of the UP configuration of that platform, native_smp_prepare_cpus() bailed out (in smp_sanity_check()) before doing the set_mtrr_aps_delayed_init() Further down the boot path, native_smp_cpus_done() will call the delayed MTRR initialization for the AP's (mtrr_aps_init()) with mtrr_aps_delayed_init not set. This resulted in the boot processor reprogramming its MTRR's to the values seen during the start of the OS boot. While this is not needed ideally, this shouldn't have caused any side-effects. This is because the reprogramming of MTRR's (set_mtrr_state() that gets called via set_mtrr()) will check if the live register contents are different from what is being asked to write and will do the actual write only if they are different. BP's mtrr state is read during the start of the OS boot and typically nothing would have changed when we ask to reprogram it on BP again because of the above scenario on an UP platform. So on a normal UP platform no reprogramming of BP MTRR MSR's happens and all is well. However, on this platform, bios seems to be modifying the fixed mtrr range registers between the start of OS boot and when we double check the live registers for reprogramming BP MTRR registers. And as the live registers are modified, we end up reprogramming the MTRR's to the state seen during the start of the OS boot. During ACPI initialization, something in the bios (probably smi handler?) don't like this fact and results in a hard lockup. We didn't see this boot hang issue on this platform before the commit d0af9eed5aa91b6b7b5049cae69e5ea956fd85c3, because only the AP's (if any) will program its MTRR's to the value that BP had at the start of the OS boot. Fix this issue by checking mtrr_aps_delayed_init before continuing further in the mtrr_aps_init(). Now, only AP's (if any) will program its MTRR's to the BP values during boot. Addresses https://bugzilla.novell.com/show_bug.cgi?id=623393 [ By the way, this behavior of the bios modifying MTRR's after the start of the OS boot is not common and the kernel is not prepared to handle this situation well. Irrespective of this issue, during suspend/resume, linux kernel will try to reprogram the BP's MTRR values to the values seen during the start of the OS boot. So suspend/resume might be already broken on this platform for all linux kernel versions. ] Reported-and-bisected-by: Markus Kohn <jabber@gmx.org> Tested-by: Markus Kohn <jabber@gmx.org> Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com> Cc: Thomas Renninger <trenn@novell.com> Cc: Rafael Wysocki <rjw@novell.com> Cc: Venkatesh Pallipadi <venki@google.com> Cc: stable@kernel.org # [v2.6.32+] LKML-Reference: <1296694975.4418.402.camel@sbsiddha-MOBL3.sc.intel.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'arch/x86/include')
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