In-Reply-To: <[email protected]>
On Tue, 21 Feb 2006 at 13:41:39 -0800, Andrew Morton wrote:
> None of these are must-have fixes, are they? I had them queued for 2.6.17.
Well i386-allow-disabling-x86_feature_sep-at-boot.patch is for me.
I had to backport it to -rc4 for testing differences between sysenter
and int80 syscall paths. I could live without it (I once forgot to apply
it and wondered why it wasn't working), but anyway here's the backport:
From: Chuck Ebbert <[email protected]>
Allow the x86 "sep" feature to be disabled at bootup. This forces use of the
int80 vsyscall. Mainly for testing or benchmarking the int80 vsyscall code.
Signed-off-by: Chuck Ebbert <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
---
Documentation/kernel-parameters.txt | 6 +++++-
arch/i386/kernel/cpu/common.c | 15 ++++++++++++++-
2 files changed, 19 insertions(+), 2 deletions(-)
--- 2.6.16-rc3-nb.orig/Documentation/kernel-parameters.txt
+++ 2.6.16-rc3-nb/Documentation/kernel-parameters.txt
@@ -1002,7 +1002,9 @@ 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]
@@ -1045,6 +1047,8 @@ 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.
--- 2.6.16-rc3-nb.orig/arch/i386/kernel/cpu/common.c
+++ 2.6.16-rc3-nb/arch/i386/kernel/cpu/common.c
@@ -22,8 +22,9 @@ DEFINE_PER_CPU(unsigned char, cpu_16bit_
EXPORT_PER_CPU_SYMBOL(cpu_16bit_stack);
static int cachesize_override __devinitdata = -1;
-static int disable_x86_fxsr __devinitdata = 0;
+static int disable_x86_fxsr __devinitdata;
static int disable_x86_serial_nr __devinitdata = 1;
+static int disable_x86_sep __devinitdata;
struct cpu_dev * cpu_devs[X86_VENDOR_NUM] = {};
@@ -183,6 +184,14 @@ 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)
{
@@ -401,6 +410,10 @@ 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);
--
Chuck
"Equations are the Devil's sentences." --Stephen Colbert
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