linux-kernel - [PATCH] [1/7] Add frame work to disable CPUID bits on the command line

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Date:	Fri, 18 Jan 2008 18:27:17 +0100 (CET)
From:	Andi Kleen <ak@...e.de>
To:	mingo@...e.hu, hpa@...or.com, tglx@...utronix.de,
	linux-kernel@...r.kernel.org
Subject: [PATCH] [1/7] Add frame work to disable CPUID bits on the command line


There are already various options to disable specific cpuid bits
on the command line. They all use their own variable. Add a generic
mask to make this easier in the future.

Signed-off-by: Andi Kleen <ak@...e.de>

---
 arch/x86/kernel/cpu/common.c |    6 ++++++
 arch/x86/kernel/setup_64.c   |    6 ++++++
 include/asm-x86/cpufeature.h |    4 ++++
 include/asm-x86/processor.h  |    1 +
 4 files changed, 17 insertions(+)

Index: linux/arch/x86/kernel/cpu/common.c
===================================================================
--- linux.orig/arch/x86/kernel/cpu/common.c
+++ linux/arch/x86/kernel/cpu/common.c
@@ -57,6 +57,8 @@ DEFINE_PER_CPU(struct gdt_page, gdt_page
 } };
 EXPORT_PER_CPU_SYMBOL_GPL(gdt_page);
 
+__u32 cleared_cpu_caps[NCAPINTS] __cpuinitdata;
+
 static int cachesize_override __cpuinitdata = -1;
 static int disable_x86_fxsr __cpuinitdata;
 static int disable_x86_serial_nr __cpuinitdata = 1;
@@ -497,6 +499,10 @@ void __cpuinit identify_cpu(struct cpuin
 			boot_cpu_data.x86_capability[i] &= c->x86_capability[i];
 	}
 
+	/* Clear all flags overriden by options */
+	for (i = 0; i < NCAPINTS; i++)
+		c->x86_capability[i] ^= cleared_cpu_caps[i];
+
 	/* Init Machine Check Exception if available. */
 	mcheck_init(c);
 
Index: linux/include/asm-x86/cpufeature.h
===================================================================
--- linux.orig/include/asm-x86/cpufeature.h
+++ linux/include/asm-x86/cpufeature.h
@@ -132,6 +132,10 @@
 
 #define set_cpu_cap(c, bit)	set_bit(bit, (unsigned long *)((c)->x86_capability))
 #define clear_cpu_cap(c, bit)	clear_bit(bit, (unsigned long *)((c)->x86_capability))
+#define setup_clear_cpu_cap(bit) do { \
+	clear_cpu_cap(&boot_cpu_data, bit);	\
+	set_bit(bit, cleared_cpu_caps); 	\
+} while (0)
 
 #define cpu_has_fpu		boot_cpu_has(X86_FEATURE_FPU)
 #define cpu_has_vme		boot_cpu_has(X86_FEATURE_VME)
Index: linux/include/asm-x86/processor.h
===================================================================
--- linux.orig/include/asm-x86/processor.h
+++ linux/include/asm-x86/processor.h
@@ -118,6 +118,7 @@ struct cpuinfo_x86 {
 extern struct cpuinfo_x86 boot_cpu_data;
 extern struct cpuinfo_x86 new_cpu_data;
 extern struct tss_struct doublefault_tss;
+extern __u32 cleared_cpu_caps[NCAPINTS];
 
 #ifdef CONFIG_SMP
 DECLARE_PER_CPU(struct cpuinfo_x86, cpu_info);
Index: linux/arch/x86/kernel/setup_64.c
===================================================================
--- linux.orig/arch/x86/kernel/setup_64.c
+++ linux/arch/x86/kernel/setup_64.c
@@ -82,6 +82,8 @@
 struct cpuinfo_x86 boot_cpu_data __read_mostly;
 EXPORT_SYMBOL(boot_cpu_data);
 
+__u32 cleared_cpu_caps[NCAPINTS] __cpuinitdata;
+
 unsigned long mmu_cr4_features;
 
 /* Boot loader ID as an integer, for the benefit of proc_dointvec */
@@ -1012,6 +1014,10 @@ void __cpuinit identify_cpu(struct cpuin
 			boot_cpu_data.x86_capability[i] &= c->x86_capability[i];
 	}
 
+	/* Clear all flags overriden by options */
+	for (i = 0; i < NCAPINTS; i++)
+		c->x86_capability[i] ^= cleared_cpu_caps[i];
+
 #ifdef CONFIG_X86_MCE
 	mcheck_init(c);
 #endif
--
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