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: Andy Lutomirski <luto@kernel.org>
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Chang 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: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/entry/vdso/vgetcpu.c b/arch/x86/entry/vdso/vgetcpu.c
index 8ec3d1f..de78fc9 100644 (file)
--- a/arch/x86/entry/vdso/vgetcpu.c
+++ b/arch/x86/entry/vdso/vgetcpu.c
@@ -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;
 }
 

diff --git a/arch/x86/entry/vdso/vma.c b/arch/x86/entry/vdso/vma.c
index 0b114aa..39b5584 100644 (file)
--- a/arch/x86/entry/vdso/vma.c
+++ b/arch/x86/entry/vdso/vma.c
@@ -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 */

diff --git a/arch/x86/include/asm/segment.h b/arch/x86/include/asm/segment.h
index e3e788e..4d1f6cc 100644 (file)
--- a/arch/x86/include/asm/segment.h
+++ b/arch/x86/include/asm/segment.h
@@ -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__
 
 /*

diff --git a/arch/x86/include/asm/vgtod.h b/arch/x86/include/asm/vgtod.h
index 4e81ea9..056a61c 100644 (file)
--- a/arch/x86/include/asm/vgtod.h
+++ b/arch/x86/include/asm/vgtod.h
@@ -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 */