On Thu, Jan 15, 2015 at 09:22:09PM -0000, Thomas Gleixner wrote:
> 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 <[email protected]>
> ---
> 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);
Let's do
struct msr m;
if (msr_read(MSR_IA32_APICBASE, &m))
return false;
return m.l & X2APIC_ENABLE;
so that we do the safe MSR access too. Who knows where this code gets
executed in the future.
> +}
> +
> #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();
... and then there's
#define x2apic_supported() (cpu_has_x2apic)
which does the cpufeature test.
Can we agree on one interface only and simplify this a bit more?
> }
>
> #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");
> }
>
>
>
>
--
Regards/Gruss,
Boris.
Sent from a fat crate under my desk. Formatting is fine.
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