Commit b2e2ba57 authored by Chang S. Bae's avatar Chang S. Bae Committed by Ingo Molnar
Browse files

x86/vdso: Initialize the CPU/node NR segment descriptor earlier 



Currently the CPU/node NR segment descriptor (GDT_ENTRY_CPU_NUMBER) is
initialized relatively late during CPU init, from the vCPU code, which
has a number of disadvantages, such as hotplug CPU notifiers and SMP
cross-calls.

Instead just initialize it much earlier, directly in cpu_init().

This reduces complexity and increases robustness.

[ mingo: Wrote new changelog. ]

Suggested-by: default avatarH. Peter Anvin <hpa@zytor.com>
Suggested-by: default avatarAndy Lutomirski <luto@kernel.org>
Signed-off-by: default avatarChang S. Bae <chang.seok.bae@intel.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Markus T Metzger <markus.t.metzger@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi Shankar <ravi.v.shankar@intel.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1537312139-5580-9-git-send-email-chang.seok.bae@intel.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent ffebbaed

arch/x86/entry/vdso/vma.c

+1 −32
Original line number Diff line number Diff line
@@ -332,35 +332,6 @@ static __init int vdso_setup(char *s) 
	return 0;

}

__setup("vdso=", vdso_setup);

#endif



#ifdef CONFIG_X86_64

static void vgetcpu_cpu_init(void *arg)

{

	int cpu = smp_processor_id();

	struct desc_struct d = { };

	unsigned long cpudata = vdso_encode_cpu_node(cpu, cpu_to_node(cpu));



	if (static_cpu_has(X86_FEATURE_RDTSCP))

		write_rdtscp_aux(cpudata);



	/* Store CPU and node number in limit */

	d.limit0 = cpudata;

	d.limit1 = cpudata >> 16;



	d.type = 5;		/* RO data, expand down, accessed */

	d.dpl = 3;		/* Visible to user code */

	d.s = 1;		/* Not a system segment */

	d.p = 1;		/* Present */

	d.d = 1;		/* 32-bit */



	write_gdt_entry(get_cpu_gdt_rw(cpu), GDT_ENTRY_CPU_NUMBER, &d, DESCTYPE_S);

}



static int vgetcpu_online(unsigned int cpu)

{

	return smp_call_function_single(cpu, vgetcpu_cpu_init, NULL, 1);

}



static int __init init_vdso(void)

{
@@ -370,9 +341,7 @@ static int __init init_vdso(void) 
	init_vdso_image(&vdso_image_x32);

#endif



	/* notifier priority > KVM */

	return cpuhp_setup_state(CPUHP_AP_X86_VDSO_VMA_ONLINE,

				 "x86/vdso/vma:online", vgetcpu_online, NULL);

	return 0;

}

subsys_initcall(init_vdso);

#endif /* CONFIG_X86_64 */

arch/x86/kernel/cpu/common.c

+24 −0
Original line number Diff line number Diff line
@@ -1669,6 +1669,29 @@ static void wait_for_master_cpu(int cpu) 
#endif

}



#ifdef CONFIG_X86_64

static void setup_getcpu(int cpu)

{

	unsigned long cpudata = vdso_encode_cpu_node(cpu, early_cpu_to_node(cpu));

	struct desc_struct d = { };



	if (static_cpu_has(X86_FEATURE_RDTSCP))

		write_rdtscp_aux(cpudata);



	/* Store CPU and node number in limit. */

	d.limit0 = cpudata;

	d.limit1 = cpudata >> 16;



	d.type = 5;		/* RO data, expand down, accessed */

	d.dpl = 3;		/* Visible to user code */

	d.s = 1;		/* Not a system segment */

	d.p = 1;		/* Present */

	d.d = 1;		/* 32-bit */



	write_gdt_entry(get_cpu_gdt_rw(cpu), GDT_ENTRY_CPU_NUMBER, &d, DESCTYPE_S);

}

#endif



/*

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

 * initialized (naturally) in the bootstrap process, such as the GDT
@@ -1706,6 +1729,7 @@ void cpu_init(void) 
	    early_cpu_to_node(cpu) != NUMA_NO_NODE)

		set_numa_node(early_cpu_to_node(cpu));

#endif

	setup_getcpu(cpu);



	me = current;

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