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Commit fc0091b3 authored by Alex Nixon's avatar Alex Nixon Committed by Ingo Molnar
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x86: change init_gdt to update the gdt via write_gdt, rather than a direct write. 



By writing directly, a memory access violation can occur whilst
hotplugging a CPU if the entry was previously marked read-only.

Signed-off-by: default avatarAlex Nixon <alex.nixon@citrix.com>
Cc: Jeremy Fitzhardinge <Jeremy.Fitzhardinge@citrix.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 529d0e40

arch/x86/kernel/smpcommon.c

+10 −7
Original line number Original line Diff line number Diff line
@@ -8,18 +8,21 @@ 
DEFINE_PER_CPU(unsigned long, this_cpu_off);

DEFINE_PER_CPU(unsigned long, this_cpu_off);

EXPORT_PER_CPU_SYMBOL(this_cpu_off);

EXPORT_PER_CPU_SYMBOL(this_cpu_off);





/* Initialize the CPU's GDT.  This is either the boot CPU doing itself

/*

   (still using the master per-cpu area), or a CPU doing it for a

 * Initialize the CPU's GDT.  This is either the boot CPU doing itself

   secondary which will soon come up. */

 * (still using the master per-cpu area), or a CPU doing it for a

 * secondary which will soon come up.

 */

__cpuinit void init_gdt(int cpu)

__cpuinit void init_gdt(int cpu)

{

{

	struct desc_struct *gdt = get_cpu_gdt_table(cpu);

	struct desc_struct gdt;





	pack_descriptor(&gdt[GDT_ENTRY_PERCPU],

	pack_descriptor(&gdt, __per_cpu_offset[cpu], 0xFFFFF,

			__per_cpu_offset[cpu], 0xFFFFF,

			0x2 | DESCTYPE_S, 0x8);

			0x2 | DESCTYPE_S, 0x8);

	gdt.s = 1;





	gdt[GDT_ENTRY_PERCPU].s = 1;

	write_gdt_entry(get_cpu_gdt_table(cpu),

			GDT_ENTRY_PERCPU, &gdt, DESCTYPE_S);





	per_cpu(this_cpu_off, cpu) = __per_cpu_offset[cpu];

	per_cpu(this_cpu_off, cpu) = __per_cpu_offset[cpu];

	per_cpu(cpu_number, cpu) = cpu;

	per_cpu(cpu_number, cpu) = cpu;