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Commit b12d8db8 authored by Tejun Heo's avatar Tejun Heo Committed by Ingo Molnar
Browse files

x86: make pda a percpu variable 



[ Based on original patch from Christoph Lameter and Mike Travis. ]

As pda is now allocated in percpu area, it can easily be made a proper
percpu variable.  Make it so by defining per cpu symbol from linker
script and declaring it in C code for SMP and simply defining it for
UP.  This change cleans up code and brings SMP and UP closer a bit.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 9939ddaf

arch/x86/include/asm/pda.h

+3 −2
Original line number Diff line number Diff line
@@ -7,6 +7,7 @@ 
#include <linux/cache.h>

#include <linux/threads.h>

#include <asm/page.h>

#include <asm/percpu.h>



/* Per processor datastructure. %gs points to it while the kernel runs */

struct x8664_pda {
@@ -39,10 +40,10 @@ struct x8664_pda { 
	unsigned irq_spurious_count;

} ____cacheline_aligned_in_smp;



extern struct x8664_pda *_cpu_pda[NR_CPUS];

DECLARE_PER_CPU(struct x8664_pda, __pda);

extern void pda_init(int);



#define cpu_pda(i) (_cpu_pda[i])

#define cpu_pda(cpu)		(&per_cpu(__pda, cpu))



/*

 * There is no fast way to get the base address of the PDA, all the accesses

arch/x86/kernel/cpu/common.c

+0 −3
Original line number Diff line number Diff line
@@ -879,9 +879,6 @@ static __init int setup_disablecpuid(char *arg) 
__setup("clearcpuid=", setup_disablecpuid);



#ifdef CONFIG_X86_64

struct x8664_pda *_cpu_pda[NR_CPUS] __read_mostly;

EXPORT_SYMBOL(_cpu_pda);



struct desc_ptr idt_descr = { 256 * 16 - 1, (unsigned long) idt_table };



static char boot_cpu_stack[IRQSTACKSIZE] __page_aligned_bss;

arch/x86/kernel/head64.c

+0 −10
Original line number Diff line number Diff line
@@ -26,18 +26,8 @@ 
#include <asm/bios_ebda.h>

#include <asm/trampoline.h>



#ifndef CONFIG_SMP

/* boot cpu pda, referenced by head_64.S to initialize %gs on UP */

struct x8664_pda _boot_cpu_pda;

#endif



void __init x86_64_init_pda(void)

{

#ifdef CONFIG_SMP

	cpu_pda(0) = (void *)__per_cpu_load;

#else

	cpu_pda(0) = &_boot_cpu_pda;

#endif

	pda_init(0);

}

arch/x86/kernel/head_64.S

+3 −2
Original line number Diff line number Diff line
@@ -19,6 +19,7 @@ 
#include <asm/msr.h>

#include <asm/cache.h>

#include <asm/processor-flags.h>

#include <asm/percpu.h>



#ifdef CONFIG_PARAVIRT

#include <asm/asm-offsets.h>
@@ -250,7 +251,7 @@ ENTRY(secondary_startup_64) 
	 * secondary CPU,initial_gs should be set to its pda address

	 * before the CPU runs this code.

	 *

	 * On UP, initial_gs points to _boot_cpu_pda and doesn't

	 * On UP, initial_gs points to PER_CPU_VAR(__pda) and doesn't

	 * change.

	 */

	movl	$MSR_GS_BASE,%ecx
@@ -284,7 +285,7 @@ ENTRY(secondary_startup_64) 
#ifdef CONFIG_SMP

	.quad	__per_cpu_load

#else

	.quad	_boot_cpu_pda

	.quad	PER_CPU_VAR(__pda)

#endif

	__FINITDATA

arch/x86/kernel/setup_percpu.c

+14 −2
Original line number Diff line number Diff line
@@ -66,6 +66,16 @@ static void __init setup_node_to_cpumask_map(void); 
static inline void setup_node_to_cpumask_map(void) { }

#endif



/*

 * Define load_pda_offset() and per-cpu __pda for x86_64.

 * load_pda_offset() is responsible for loading the offset of pda into

 * %gs.

 *

 * On SMP, pda offset also duals as percpu base address and thus it

 * should be at the start of per-cpu area.  To achieve this, it's

 * preallocated in vmlinux_64.lds.S directly instead of using

 * DEFINE_PER_CPU().

 */

#ifdef CONFIG_X86_64

void __cpuinit load_pda_offset(int cpu)

{
@@ -74,6 +84,10 @@ void __cpuinit load_pda_offset(int cpu) 
	wrmsrl(MSR_GS_BASE, cpu_pda(cpu));

	mb();

}

#ifndef CONFIG_SMP

DEFINE_PER_CPU(struct x8664_pda, __pda);

EXPORT_PER_CPU_SYMBOL(__pda);

#endif



#endif /* CONFIG_SMP && CONFIG_X86_64 */
@@ -180,8 +194,6 @@ void __init setup_per_cpu_areas(void) 
		memcpy(ptr, __per_cpu_load, __per_cpu_end - __per_cpu_start);

		per_cpu_offset(cpu) = ptr - __per_cpu_start;

#ifdef CONFIG_X86_64

		cpu_pda(cpu) = (void *)ptr;



		/*

		 * CPU0 modified pda in the init data area, reload pda

		 * offset for CPU0 and clear the area for others.