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| author | Chuck Ebbert <76306.1226@compuserve.com> | 2006-03-23 02:59:34 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@g5.osdl.org> | 2006-03-23 07:38:04 -0800 |
| commit | 4f88651125e2ca8b106b6f65b65ea45776517bf3 (patch) | |
| tree | a9865c268c57bd1752a66899615d8694d5ddaea8 | |
| parent | 3bc9b76bede9b3c72088258c7e72eb823f3351d4 (diff) | |
| download | lwn-4f88651125e2ca8b106b6f65b65ea45776517bf3.tar.gz lwn-4f88651125e2ca8b106b6f65b65ea45776517bf3.zip | |
[PATCH] i386: allow disabling X86_FEATURE_SEP at boot
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 <76306.1226@compuserve.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
| -rw-r--r-- | Documentation/kernel-parameters.txt | 6 | ||||
| -rw-r--r-- | arch/i386/kernel/cpu/common.c | 15 |
2 files changed, 19 insertions, 2 deletions
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index fc99075e0af4..880be3a30d8d 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -1008,7 +1008,9 @@ 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] @@ -1053,6 +1055,8 @@ 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. diff --git a/arch/i386/kernel/cpu/common.c b/arch/i386/kernel/cpu/common.c index f63dcfb16dad..bbfc278dfa49 100644 --- a/arch/i386/kernel/cpu/common.c +++ b/arch/i386/kernel/cpu/common.c @@ -26,8 +26,9 @@ DEFINE_PER_CPU(unsigned char, cpu_16bit_stack[CPU_16BIT_STACK_SIZE]); EXPORT_PER_CPU_SYMBOL(cpu_16bit_stack); static int cachesize_override __cpuinitdata = -1; -static int disable_x86_fxsr __cpuinitdata = 0; +static int disable_x86_fxsr __cpuinitdata; static int disable_x86_serial_nr __cpuinitdata = 1; +static int disable_x86_sep __cpuinitdata; struct cpu_dev * cpu_devs[X86_VENDOR_NUM] = {}; @@ -187,6 +188,14 @@ static int __init x86_fxsr_setup(char * s) __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) { @@ -405,6 +414,10 @@ void __cpuinit identify_cpu(struct cpuinfo_x86 *c) 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); |