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

x86/vdso: Introduce helper functions for CPU and node number 



Clean up the CPU/node number related code a bit, to make it more apparent
how we are encoding/extracting the CPU and node fields from the
segment limit.

No change in functionality intended.

[ mingo: Wrote new changelog. ]

Suggested-by: default avatarAndy Lutomirski <luto@kernel.org>
Suggested-by: default avatarThomas Gleixner <tglx@linutronix.de>
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: H. Peter Anvin <hpa@zytor.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>
Link: http://lkml.kernel.org/r/1537312139-5580-8-git-send-email-chang.seok.bae@intel.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent c4755613

arch/x86/entry/vdso/vgetcpu.c

+1 −8
Original line number Diff line number Diff line
@@ -13,14 +13,7 @@ 
notrace long

__vdso_getcpu(unsigned *cpu, unsigned *node, struct getcpu_cache *unused)

{

	unsigned int p;



	p = __getcpu();



	if (cpu)

		*cpu = p & VGETCPU_CPU_MASK;

	if (node)

		*node = p >> 12;

	vdso_read_cpu_node(cpu, node);

	return 0;

}

arch/x86/entry/vdso/vma.c

+7 −12
Original line number Diff line number Diff line
@@ -339,20 +339,15 @@ static void vgetcpu_cpu_init(void *arg) 
{

	int cpu = smp_processor_id();

	struct desc_struct d = { };

	unsigned long node = 0;

#ifdef CONFIG_NUMA

	node = cpu_to_node(cpu);

#endif

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



	if (static_cpu_has(X86_FEATURE_RDTSCP))

		write_rdtscp_aux((node << 12) | cpu);

		write_rdtscp_aux(cpudata);



	/* Store CPU and node number in limit */

	d.limit0 = cpudata;

	d.limit1 = cpudata >> 16;



	/*

	 * Store cpu number in limit so that it can be loaded

	 * quickly in user space in vgetcpu. (12 bits for the CPU

	 * and 8 bits for the node)

	 */

	d.limit0 = cpu | ((node & 0xf) << 12);

	d.limit1 = node >> 4;

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

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

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

arch/x86/include/asm/segment.h

+41 −0
Original line number Diff line number Diff line
@@ -224,6 +224,47 @@ 
#define GDT_ENTRY_TLS_ENTRIES		3

#define TLS_SIZE			(GDT_ENTRY_TLS_ENTRIES* 8)



#ifdef CONFIG_X86_64



/* Bit size and mask of CPU number stored in the per CPU data (and TSC_AUX) */

#define VDSO_CPU_SIZE			12

#define VDSO_CPU_MASK			0xfff



#ifndef __ASSEMBLY__



/* Helper functions to store/load CPU and node numbers */



static inline unsigned long vdso_encode_cpu_node(int cpu, unsigned long node)

{

	return ((node << VDSO_CPU_SIZE) | cpu);

}



static inline void vdso_read_cpu_node(unsigned *cpu, unsigned *node)

{

	unsigned int p;



	/*

	 * Load CPU and node number from GDT.  LSL is faster than RDTSCP

	 * and works on all CPUs.  This is volatile so that it orders

	 * correctly with respect to barrier() and to keep GCC from cleverly

	 * hoisting it out of the calling function.

	 *

	 * If RDPID is available, use it.

	 */

	alternative_io ("lsl %[seg],%[p]",

			".byte 0xf3,0x0f,0xc7,0xf8", /* RDPID %eax/rax */

			X86_FEATURE_RDPID,

			[p] "=a" (p), [seg] "r" (__CPU_NUMBER_SEG));



	if (cpu)

		*cpu = (p & VDSO_CPU_MASK);

	if (node)

		*node = (p >> VDSO_CPU_SIZE);

}



#endif /* !__ASSEMBLY__ */

#endif /* CONFIG_X86_64 */



#ifdef __KERNEL__



/*

arch/x86/include/asm/vgtod.h

+0 −26
Original line number Diff line number Diff line
@@ -77,30 +77,4 @@ static inline void gtod_write_end(struct vsyscall_gtod_data *s) 
	++s->seq;

}



#ifdef CONFIG_X86_64



#define VGETCPU_CPU_MASK 0xfff



static inline unsigned int __getcpu(void)

{

	unsigned int p;



	/*

	 * Load CPU (and node) number from GDT.  LSL is faster than RDTSCP

	 * and works on all CPUs.  This is volatile so that it orders

	 * correctly with respect to barrier() and to keep GCC from cleverly

	 * hoisting it out of the calling function.

	 *

	 * If RDPID is available, use it.

	 */

	alternative_io ("lsl %[seg],%[p]",

			".byte 0xf3,0x0f,0xc7,0xf8", /* RDPID %eax/rax */

			X86_FEATURE_RDPID,

			[p] "=a" (p), [seg] "r" (__CPU_NUMBER_SEG));



	return p;

}



#endif /* CONFIG_X86_64 */



#endif /* _ASM_X86_VGTOD_H */

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