diff options
| -rw-r--r-- | arch/x86/include/asm/processor.h | 1 | ||||
| -rw-r--r-- | arch/x86/kernel/cpu/common.c | 47 |
2 files changed, 31 insertions, 17 deletions
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h index 67c9d73b31fa..e21ec970d41a 100644 --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -670,7 +670,6 @@ extern struct desc_ptr early_gdt_descr; extern void switch_to_new_gdt(int); extern void load_direct_gdt(int); extern void load_fixmap_gdt(int); -extern void load_percpu_segment(int); extern void cpu_init(void); extern void cpu_init_secondary(void); extern void cpu_init_exception_handling(void); diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 3e508f239098..c09abee6f4d5 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -701,16 +701,6 @@ static const char *table_lookup_model(struct cpuinfo_x86 *c) __u32 cpu_caps_cleared[NCAPINTS + NBUGINTS] __aligned(sizeof(unsigned long)); __u32 cpu_caps_set[NCAPINTS + NBUGINTS] __aligned(sizeof(unsigned long)); -void load_percpu_segment(int cpu) -{ -#ifdef CONFIG_X86_32 - loadsegment(fs, __KERNEL_PERCPU); -#else - __loadsegment_simple(gs, 0); - wrmsrl(MSR_GS_BASE, cpu_kernelmode_gs_base(cpu)); -#endif -} - #ifdef CONFIG_X86_32 /* The 32-bit entry code needs to find cpu_entry_area. */ DEFINE_PER_CPU(struct cpu_entry_area *, cpu_entry_area); @@ -738,16 +728,41 @@ void load_fixmap_gdt(int cpu) } EXPORT_SYMBOL_GPL(load_fixmap_gdt); -/* - * Current gdt points %fs at the "master" per-cpu area: after this, - * it's on the real one. +/** + * switch_to_new_gdt - Switch form early GDT to the direct one + * @cpu: The CPU number for which this is invoked + * + * Invoked during early boot to switch from early GDT and early per CPU + * (%fs on 32bit, GS_BASE on 64bit) to the direct GDT and the runtime per + * CPU area. */ void switch_to_new_gdt(int cpu) { - /* Load the original GDT */ load_direct_gdt(cpu); - /* Reload the per-cpu base */ - load_percpu_segment(cpu); + +#ifdef CONFIG_X86_64 + /* + * No need to load %gs. It is already correct. + * + * Writing %gs on 64bit would zero GSBASE which would make any per + * CPU operation up to the point of the wrmsrl() fault. + * + * Set GSBASE to the new offset. Until the wrmsrl() happens the + * early mapping is still valid. That means the GSBASE update will + * lose any prior per CPU data which was not copied over in + * setup_per_cpu_areas(). + */ + wrmsrl(MSR_GS_BASE, cpu_kernelmode_gs_base(cpu)); +#else + /* + * %fs is already set to __KERNEL_PERCPU, but after switching GDT + * it is required to load FS again so that the 'hidden' part is + * updated from the new GDT. Up to this point the early per CPU + * translation is active. Any content of the early per CPU data + * which was not copied over in setup_per_cpu_areas() is lost. + */ + loadsegment(fs, __KERNEL_PERCPU); +#endif } static const struct cpu_dev *cpu_devs[X86_VENDOR_NUM] = {}; |