* Re: [patch 2.6.15] i386: allow disabling X86_FEATURE_SEP at boot
@ 2006-01-28 6:04 Chuck Ebbert
0 siblings, 0 replies; 3+ messages in thread
From: Chuck Ebbert @ 2006-01-28 6:04 UTC (permalink / raw)
To: Andrew Morton; +Cc: Ashok Raj, ergot86, torvalds, mingo, linux-kernel
In-Reply-To: <20060127143713.2efc16ed.akpm@osdl.org>
On Fri, 27 Jan 2006 at 14:37:13 -0800, Andrew Morton wrote:
> Chuck Ebbert <76306.1226@compuserve.com> 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?
Mainly for testing or benchmarking the int80 vsyscall code.
> > --- 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.
I'll try to do that.
> __devinit is a superset of that, but we're being a little wasteful in the
> case of CONFIG_HOTPLUG&&!CONFIG_HOTPLUG_CPU.
--
Chuck
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [patch 2.6.15] i386: allow disabling X86_FEATURE_SEP at boot
2006-01-26 18:36 Chuck Ebbert
@ 2006-01-27 22:37 ` Andrew Morton
0 siblings, 0 replies; 3+ messages in thread
From: Andrew Morton @ 2006-01-27 22:37 UTC (permalink / raw)
To: Chuck Ebbert; +Cc: linux-kernel, mingo, torvalds, ergot86, Ashok Raj
Chuck Ebbert <76306.1226@compuserve.com> 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.
^ permalink raw reply [flat|nested] 3+ messages in thread
* [patch 2.6.15] i386: allow disabling X86_FEATURE_SEP at boot
@ 2006-01-26 18:36 Chuck Ebbert
2006-01-27 22:37 ` Andrew Morton
0 siblings, 1 reply; 3+ messages in thread
From: Chuck Ebbert @ 2006-01-26 18:36 UTC (permalink / raw)
To: linux-kernel; +Cc: Andrew Morton, Ingo Molnar, Linus Torvalds, Daniel fernandez
Allow the x86 "sep" feature to be disabled at bootup. This
forces use of the int80 vsyscall.
Signed-off-by: Chuck Ebbert <76306.1226@compuserve.com>
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;
struct cpu_dev * cpu_devs[X86_VENDOR_NUM] = {};
@@ -177,6 +178,14 @@ static int __init x86_fxsr_setup(char *
__setup("nofxsr", x86_fxsr_setup);
+static int __init x86_sep_setup(char * s)
+{
+ disable_x86_sep = 1;
+ return 1;
+}
+__setup("nosep", x86_sep_setup);
+
+
/* Standard macro to see if a specific flag is changeable */
static inline int flag_is_changeable_p(u32 flag)
{
@@ -392,6 +401,10 @@ void __devinit identify_cpu(struct cpuin
clear_bit(X86_FEATURE_XMM, c->x86_capability);
}
+ /* SEP disabled? */
+ if (disable_x86_sep)
+ clear_bit(X86_FEATURE_SEP, c->x86_capability);
+
if (disable_pse)
clear_bit(X86_FEATURE_PSE, c->x86_capability);
--- 2.6.15a.orig/Documentation/kernel-parameters.txt
+++ 2.6.15a/Documentation/kernel-parameters.txt
@@ -929,7 +929,9 @@ running once the system is up.
noexec=on: enable non-executable mappings (default)
noexec=off: disable nn-executable mappings
- nofxsr [BUGS=IA-32]
+ nofxsr [BUGS=IA-32] Disables x86 floating point extended
+ register save and restore. The kernel will only save
+ legacy floating-point registers on task switch.
nohlt [BUGS=ARM]
@@ -972,6 +974,8 @@ running once the system is up.
nosbagart [IA-64]
+ nosep [BUGS=IA-32] Disables x86 SYSENTER/SYSEXIT support.
+
nosmp [SMP] Tells an SMP kernel to act as a UP kernel.
nosync [HW,M68K] Disables sync negotiation for all devices.
--
Chuck
Currently reading: _The Atrocity Archives_ by Charles Stross
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