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x86: make pda a percpu variable

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[ 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: Tejun Heo <tj@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Tejun Heo 2009-01-13 20:41:35 +09:00 committed by Ingo Molnar
parent 9939ddaff5
commit b12d8db8fb
6 changed files with 23 additions and 20 deletions
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5
arch/x86/include/asm/pda.h
View File

@ -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

3
arch/x86/kernel/cpu/common.c
View File

@ -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;

10
arch/x86/kernel/head64.c
View File

@ -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);
}

5
arch/x86/kernel/head_64.S
View File

@ -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

16
arch/x86/kernel/setup_percpu.c
View File

@ -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.

4
arch/x86/kernel/vmlinux_64.lds.S
View File

@ -217,10 +217,12 @@ SECTIONS
* percpu offsets are zero-based on SMP. PERCPU_VADDR() changes the
* output PHDR, so the next output section - __data_nosave - should
* switch it back to data.init. Also, pda should be at the head of
* percpu area. Preallocate it.
* percpu area. Preallocate it and define the percpu offset symbol
* so that it can be accessed as a percpu variable.
*/
. = ALIGN(PAGE_SIZE);
PERCPU_VADDR_PREALLOC(0, :percpu, pda_size)
per_cpu____pda = __per_cpu_start;
#else
PERCPU(PAGE_SIZE)
#endif