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Subject[patch 01/23] x86/apic: Avoid open coded x2apic detection
enable_IR_x2apic() grew a open coded x2apic detection. Implement a
proper helper function which shares the code with the already existing
x2apic_enabled().

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
arch/x86/include/asm/apic.h | 18 +++++++++---------
arch/x86/kernel/apic/apic.c | 5 +----
2 files changed, 10 insertions(+), 13 deletions(-)

Index: tip/arch/x86/include/asm/apic.h
===================================================================
--- tip.orig/arch/x86/include/asm/apic.h
+++ tip/arch/x86/include/asm/apic.h
@@ -108,6 +108,14 @@ extern u64 native_apic_icr_read(void);

extern int x2apic_mode;

+static inline bool apic_is_x2apic_enabled(void)
+{
+ u64 msr;
+
+ rdmsrl(MSR_IA32_APICBASE, msr);
+ return msr & X2APIC_ENABLE;
+}
+
#ifdef CONFIG_X86_X2APIC
/*
* Make previous memory operations globally visible before
@@ -175,15 +183,7 @@ extern void check_x2apic(void);
extern void enable_x2apic(void);
static inline int x2apic_enabled(void)
{
- u64 msr;
-
- if (!cpu_has_x2apic)
- return 0;
-
- rdmsrl(MSR_IA32_APICBASE, msr);
- if (msr & X2APIC_ENABLE)
- return 1;
- return 0;
+ return cpu_has_x2apic && apic_is_x2apic_enabled();
}

#define x2apic_supported() (cpu_has_x2apic)
Index: tip/arch/x86/kernel/apic/apic.c
===================================================================
--- tip.orig/arch/x86/kernel/apic/apic.c
+++ tip/arch/x86/kernel/apic/apic.c
@@ -1625,10 +1625,7 @@ void __init enable_IR_x2apic(void)
int ret, ir_stat;

if (!IS_ENABLED(CONFIG_X86_X2APIC)) {
- u64 msr;
-
- rdmsrl(MSR_IA32_APICBASE, msr);
- if (msr & X2APIC_ENABLE)
+ if (apic_is_x2apic_enabled())
panic("BIOS has enabled x2apic but kernel doesn't support x2apic, please disable x2apic in BIOS.\n");
}




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