Add a generic option to clear any cpuid bit. I added it because it was
very easy to add with the new generic cpuid disable bitmap and perhaps
it will be useful in the future.
Signed-off-by: Andi Kleen <[EMAIL PROTECTED]>
---
Documentation/kernel-parameters.txt | 13 +++++++++++++
arch/x86/kernel/cpu/common.c | 11 +++++++++++
arch/x86/kernel/setup_64.c | 11 +++++++++++
3 files changed, 35 insertions(+)
Index: linux/arch/x86/kernel/cpu/common.c
===================================================================
--- linux.orig/arch/x86/kernel/cpu/common.c
+++ linux/arch/x86/kernel/cpu/common.c
@@ -572,6 +572,17 @@ void __cpuinit print_cpu_info(struct cpu
printk("\n");
}
+static __init int setup_disablecpuid(char *arg)
+{
+ int bit;
+ if (get_option(&arg, &bit) && bit < NCAPINTS*32)
+ setup_clear_cpu_cap(bit);
+ else
+ return 0;
+ return 1;
+}
+__setup("clearcpuid=", setup_disablecpuid);
+
cpumask_t cpu_initialized __cpuinitdata = CPU_MASK_NONE;
/* This is hacky. :)
Index: linux/arch/x86/kernel/setup_64.c
===================================================================
--- linux.orig/arch/x86/kernel/setup_64.c
+++ linux/arch/x86/kernel/setup_64.c
@@ -1060,6 +1060,17 @@ void __cpuinit print_cpu_info(struct cpu
printk(KERN_CONT "\n");
}
+static __init int setup_disablecpuid(char *arg)
+{
+ int bit;
+ if (get_option(&arg, &bit) && bit < NCAPINTS*32)
+ setup_clear_cpu_cap(bit);
+ else
+ return 0;
+ return 1;
+}
+__setup("clearcpuid=", setup_disablecpuid);
+
/*
* Get CPU information for use by the procfs.
*/
Index: linux/Documentation/kernel-parameters.txt
===================================================================
--- linux.orig/Documentation/kernel-parameters.txt
+++ linux/Documentation/kernel-parameters.txt
@@ -408,6 +408,19 @@ and is between 256 and 4096 characters.
[SPARC64] tick
[X86-64] hpet,tsc
+ clearcpuid=BITNUM [X86]
+ Disable CPUID feature X for the kernel. See
+ include/asm-x86/cpufeature.h for the valid bit numbers.
+ Note the Linux specific bits are not necessarily
+ stable over kernel options, but the vendor specific
+ ones should be.
+ Also note that user programs calling CPUID directly
+ or using the feature without checking anything
+ will still see it. This just prevents it from
+ being used by the kernel or shown in /proc/cpuinfo.
+ Also note the kernel might malfunction if you disable
+ some critical bits.
+
code_bytes [IA32/X86_64] How many bytes of object code to print
in an oops report.
Range: 0 - 8192
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