Re: [patch 2.6.15] i386: allow disabling X86_FEATURE_SEP at boot

[Andrew Morton]

Chuck Ebbert <76306.1226@xxxxxxxxxxxxxx> wrote:
>
> Allow the x86 "sep" feature to be disabled at bootup.  This
> forces use of the int80 vsyscall.
> 

Why is there a need to do this?

> 
>  Documentation/kernel-parameters.txt |    6 +++++-
>  arch/i386/kernel/cpu/common.c       |   13 +++++++++++++
>  2 files changed, 18 insertions(+), 1 deletion(-)
> 
> --- 2.6.15a.orig/arch/i386/kernel/cpu/common.c
> +++ 2.6.15a/arch/i386/kernel/cpu/common.c
> @@ -27,6 +27,7 @@ EXPORT_PER_CPU_SYMBOL(cpu_16bit_stack);
>  static int cachesize_override __devinitdata = -1;
>  static int disable_x86_fxsr __devinitdata = 0;
>  static int disable_x86_serial_nr __devinitdata = 1;
> +static int disable_x86_sep __devinitdata = 0;
>  

hm, I guess lots of things in there should be __cpuinit/__cpuinitdata. 
__devinit is a superset of that, but we're being a little wasteful in the
case of CONFIG_HOTPLUG&&!CONFIG_HOTPLUG_CPU.
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