Commit c5413fbe authored by Jeremy Fitzhardinge's avatar Jeremy Fitzhardinge Committed by Andi Kleen
Browse files

[PATCH] i386: Fix UP gdt bugs 



Fixes two problems with the GDT when compiling for uniprocessor:
 - There's no percpu segment, so trying to load its selector into %fs fails.
   Use a null selector instead.
 - The real gdt needs to be loaded at some point.  Do it in cpu_init().

Signed-off-by: default avatarChris Wright <chrisw@sous-sol.org>
Signed-off-by: default avatarJeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: default avatarAndi Kleen <ak@suse.de>
Cc: Rusty Russell <rusty@rustcorp.com.au>
parent 1956c73b

arch/i386/kernel/cpu/common.c

+13 −0
Original line number Diff line number Diff line
@@ -638,6 +638,18 @@ struct pt_regs * __devinit idle_regs(struct pt_regs *regs) 
	return regs;

}



/* Current gdt points %fs at the "master" per-cpu area: after this,

 * it's on the real one. */

void switch_to_new_gdt(void)

{

	struct Xgt_desc_struct gdt_descr;



	gdt_descr.address = (long)get_cpu_gdt_table(smp_processor_id());

	gdt_descr.size = GDT_SIZE - 1;

	load_gdt(&gdt_descr);

	asm("mov %0, %%fs" : : "r" (__KERNEL_PERCPU) : "memory");

}



/*

 * cpu_init() initializes state that is per-CPU. Some data is already

 * initialized (naturally) in the bootstrap process, such as the GDT
@@ -668,6 +680,7 @@ void __cpuinit cpu_init(void) 
	}



	load_idt(&idt_descr);

	switch_to_new_gdt();



	/*

	 * Set up and load the per-CPU TSS and LDT

arch/i386/kernel/smpboot.c

+0 −12
Original line number Diff line number Diff line
@@ -1177,18 +1177,6 @@ void __init native_smp_prepare_cpus(unsigned int max_cpus) 
	smp_boot_cpus(max_cpus);

}



/* Current gdt points %fs at the "master" per-cpu area: after this,

 * it's on the real one. */

static inline void switch_to_new_gdt(void)

{

	struct Xgt_desc_struct gdt_descr;



	gdt_descr.address = (long)get_cpu_gdt_table(smp_processor_id());

	gdt_descr.size = GDT_SIZE - 1;

	load_gdt(&gdt_descr);

	asm("mov %0, %%fs" : : "r" (__KERNEL_PERCPU) : "memory");

}



void __init native_smp_prepare_boot_cpu(void)

{

	unsigned int cpu = smp_processor_id();

include/asm-i386/processor.h

+1 −0
Original line number Diff line number Diff line
@@ -750,6 +750,7 @@ extern void enable_sep_cpu(void); 
extern int sysenter_setup(void);



extern void cpu_set_gdt(int);

extern void switch_to_new_gdt(void);

extern void cpu_init(void);



extern int force_mwait;

include/asm-i386/segment.h

+4 −0
Original line number Diff line number Diff line
@@ -75,7 +75,11 @@ 
#define __ESPFIX_SS (GDT_ENTRY_ESPFIX_SS * 8)



#define GDT_ENTRY_PERCPU			(GDT_ENTRY_KERNEL_BASE + 15)

#ifdef CONFIG_SMP

#define __KERNEL_PERCPU (GDT_ENTRY_PERCPU * 8)

#else

#define __KERNEL_PERCPU 0

#endif



#define GDT_ENTRY_DOUBLEFAULT_TSS	31

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