RE: [PATCH] 2.4.23-rc1: cpu_sibling_map fix

[Nakajima, Jun]

Can you please explain why the information by CPUID does not work for
summit-based machine? The CPUID does not reflect the H/W configuration,
and the BIOS needs to communicate via local APIC Ids instead?

	Jun

> -----Original Message-----
> From: linux-kernel-owner@xxxxxxxxxxxxxxx [mailto:linux-kernel-
> owner@xxxxxxxxxxxxxxx] On Behalf Of James Cleverdon
> Sent: Wednesday, November 12, 2003 7:57 PM
> To: linux-kernel@xxxxxxxxxxxxxxx; Marcelo Tosatti
> Subject: [PATCH] 2.4.23-rc1: cpu_sibling_map fix
> 
> On summit-based machines the cpu_sibling_map data has been hosed for
some
> time.  I found out why in Intel's IA-32 Software Deveveopers' Manual
Vol 2
> under CPUID.  Looks like the value that cpuid returns is the one
latched
> at
> reset, and doesn't reflect any changes made by the BIOS later:
> 
> 	* Local APIC ID (high byte of EBX)--this number is the 8-bit ID
that
> is
> 	  assigned to the local APIC on the processor during power up.
This
> field
> 	  was introduced in the Pentium 4 processor.
> 
> Also, the code in init_intel was a bit overdesigned.  Until Intel
releases
> a
> chip with a non-power-of-2 sibling count on it, there's no point in
all
> that
> bit bashing.
> 
> 
> diff -pru 2.4.23-rc1/arch/i386/kernel/setup.c
rc1/arch/i386/kernel/setup.c
> --- 2.4.23-rc1/arch/i386/kernel/setup.c	2003-11-11
18:09:57.000000000 -
> 0800
> +++ rc1/arch/i386/kernel/setup.c	2003-11-12 15:18:44.000000000
-0800
> @@ -2461,8 +2461,6 @@ static void __init init_intel(struct cpu
>  		extern	int phys_proc_id[NR_CPUS];
> 
>  		u32 	eax, ebx, ecx, edx;
> -		int 	index_lsb, index_msb, tmp;
> -		int	initial_apic_id;
>  		int 	cpu = smp_processor_id();
> 
>  		cpuid(1, &eax, &ebx, &ecx, &edx);
> @@ -2471,11 +2469,10 @@ static void __init init_intel(struct cpu
>  		if (smp_num_siblings == 1) {
>  			printk(KERN_INFO  "CPU: Hyper-Threading is
disabled\n");
>  		} else if (smp_num_siblings > 1 ) {
> -			index_lsb = 0;
> -			index_msb = 31;
>  			/*
>  			 * At this point we only support two siblings
per
> -			 * processor package.
> +			 * processor package.  Assume will be power of 2
until
> +			 * we learn otherwise.
>  			 */
>  #define NR_SIBLINGS	2
>  			if (smp_num_siblings != NR_SIBLINGS) {
> @@ -2483,20 +2480,7 @@ static void __init init_intel(struct cpu
>  				smp_num_siblings = 1;
>  				return;
>  			}
> -			tmp = smp_num_siblings;
> -			while ((tmp & 1) == 0) {
> -				tmp >>=1 ;
> -				index_lsb++;
> -			}
> -			tmp = smp_num_siblings;
> -			while ((tmp & 0x80000000 ) == 0) {
> -				tmp <<=1 ;
> -				index_msb--;
> -			}
> -			if (index_lsb != index_msb )
> -				index_msb++;
> -			initial_apic_id = ebx >> 24 & 0xff;
> -			phys_proc_id[cpu] = initial_apic_id >>
index_msb;
> +			phys_proc_id[cpu] = hard_smp_processor_id() &
> ~(smp_num_siblings - 1);
> 
>  			printk(KERN_INFO  "CPU: Physical Processor ID:
%d\n",
>                                 phys_proc_id[cpu]);
> diff -pru 2.4.23-rc1/include/asm-i386/apicdef.h rc1/include/asm-
> i386/apicdef.h
> --- 2.4.23-rc1/include/asm-i386/apicdef.h	2003-08-25
04:44:43.000000000 -
> 0700
> +++ rc1/include/asm-i386/apicdef.h	2003-11-12 16:32:54.000000000
-0800
> @@ -11,8 +11,8 @@
>  #define		APIC_DEFAULT_PHYS_BASE	0xfee00000
> 
>  #define		APIC_ID		0x20
> -#define			APIC_ID_MASK		(0x0F<<24)
> -#define			GET_APIC_ID(x)		(((x)>>24)&0x0F)
> +#define			APIC_ID_MASK		(0xFFu<<24)
> +#define			GET_APIC_ID(x)
(((unsigned)(x)>>24)&0xFF)
>  #define		APIC_LVR	0x30
>  #define			APIC_LVR_MASK		0xFF00FF
>  #define			GET_APIC_VERSION(x)	((x)&0xFF)
-
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