From ac72e7888a612dccfbc15b34698aad441bdfda10 Mon Sep 17 00:00:00 2001
From: Andi Kleen <ak@suse.de>
Date: Wed, 30 Jan 2008 13:33:21 +0100
Subject: [PATCH] x86: add generic clearcpuid=... option
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 <ak@suse.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
Documentation/kernel-parameters.txt | 13 +++++++++++++
arch/x86/kernel/cpu/common.c | 11 +++++++++++
arch/x86/kernel/setup_64.c | 11 +++++++++++
3 files changed, 35 insertions(+)
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 040e30a33b7c..50d564dabb13 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -416,6 +416,19 @@ and is between 256 and 4096 characters. It is defined in the file
[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
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 56b7ea8e6c79..56cc341cc586 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -572,6 +572,17 @@ void __cpuinit print_cpu_info(struct cpuinfo_x86 *c)
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. :)
diff --git a/arch/x86/kernel/setup_64.c b/arch/x86/kernel/setup_64.c
index cb9b8a90c094..79635b7bd57a 100644
--- a/arch/x86/kernel/setup_64.c
+++ b/arch/x86/kernel/setup_64.c
@@ -1050,6 +1050,17 @@ void __cpuinit print_cpu_info(struct cpuinfo_x86 *c)
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.
*/