Commit f32ff538 authored by Tejun Heo's avatar Tejun Heo Committed by Ingo Molnar
Browse files

x86: load pointer to pda into %gs while brining up a CPU 



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

CPU startup code in head_64.S loaded address of a zero page into %gs
for temporary use till pda is loaded but address to the actual pda is
available at the point.  Load the real address directly instead.

This will help unifying percpu and pda handling later on.

This patch is mostly taken from Mike Travis' "x86_64: Fold pda into
per cpu area" patch.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent 3e5d8f97

arch/x86/include/asm/trampoline.h

+1 −0
Original line number Diff line number Diff line
@@ -13,6 +13,7 @@ extern unsigned char *trampoline_base; 


extern unsigned long init_rsp;

extern unsigned long initial_code;

extern unsigned long initial_gs;



#define TRAMPOLINE_SIZE roundup(trampoline_end - trampoline_data, PAGE_SIZE)

#define TRAMPOLINE_BASE 0x6000

arch/x86/kernel/acpi/sleep.c

+1 −0
Original line number Diff line number Diff line
@@ -101,6 +101,7 @@ int acpi_save_state_mem(void) 
	stack_start.sp = temp_stack + sizeof(temp_stack);

	early_gdt_descr.address =

			(unsigned long)get_cpu_gdt_table(smp_processor_id());

	initial_gs = (unsigned long)cpu_pda(smp_processor_id());

#endif

	initial_code = (unsigned long)wakeup_long64;

	saved_magic = 0x123456789abcdef0;

arch/x86/kernel/head64.c

+2 −2
Original line number Diff line number Diff line
@@ -26,8 +26,8 @@ 
#include <asm/bios_ebda.h>

#include <asm/trampoline.h>



/* boot cpu pda */

static struct x8664_pda _boot_cpu_pda;

/* boot cpu pda, referenced by head_64.S to initialize %gs for boot CPU */

struct x8664_pda _boot_cpu_pda;



#ifdef CONFIG_SMP

/*

arch/x86/kernel/head_64.S

+10 −5
Original line number Diff line number Diff line
@@ -243,12 +243,15 @@ ENTRY(secondary_startup_64) 
	movl %eax,%fs

	movl %eax,%gs



	/* 

	 * Setup up a dummy PDA. this is just for some early bootup code

	 * that does in_interrupt() 

	/* Set up %gs.

	 *

	 * %gs should point to the pda.  For initial boot, make %gs point

	 * to the _boot_cpu_pda in data section.  For a secondary CPU,

	 * initial_gs should be set to its pda address before the CPU runs

	 * this code.

	 */

	movl	$MSR_GS_BASE,%ecx

	movq	$empty_zero_page,%rax

	movq	initial_gs(%rip),%rax

	movq    %rax,%rdx

	shrq	$32,%rdx

	wrmsr
@@ -274,6 +277,8 @@ ENTRY(secondary_startup_64) 
	.align	8

	ENTRY(initial_code)

	.quad	x86_64_start_kernel

	ENTRY(initial_gs)

	.quad	_boot_cpu_pda

	__FINITDATA



	ENTRY(stack_start)

arch/x86/kernel/smpboot.c

+1 −0
Original line number Diff line number Diff line
@@ -854,6 +854,7 @@ do_rest: 
#else

	cpu_pda(cpu)->pcurrent = c_idle.idle;

	clear_tsk_thread_flag(c_idle.idle, TIF_FORK);

	initial_gs = (unsigned long)cpu_pda(cpu);

#endif

	early_gdt_descr.address = (unsigned long)get_cpu_gdt_table(cpu);

	initial_code = (unsigned long)start_secondary;

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