[PATCH] i386: Convert PDA into the percpu section
Currently x86 (similar to x84-64) has a special per-cpu structure
called "i386_pda" which can be easily and efficiently referenced via
the %fs register. An ELF section is more flexible than a structure,
allowing any piece of code to use this area. Indeed, such a section
already exists: the per-cpu area.
So this patch:
(1) Removes the PDA and uses per-cpu variables for each current member.
(2) Replaces the __KERNEL_PDA segment with __KERNEL_PERCPU.
(3) Creates a per-cpu mirror of __per_cpu_offset called this_cpu_off, which
can be used to calculate addresses for this CPU's variables.
(4) Simplifies startup, because %fs doesn't need to be loaded with a
special segment at early boot; it can be deferred until the first
percpu area is allocated (or never for UP).
The result is less code and one less x86-specific concept.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Cc: Andi Kleen <ak@suse.de>
diff --git a/include/asm-i386/percpu.h b/include/asm-i386/percpu.h
index a10e7c6..c5f12f0 100644
--- a/include/asm-i386/percpu.h
+++ b/include/asm-i386/percpu.h
@@ -1,9 +1,30 @@
#ifndef __ARCH_I386_PERCPU__
#define __ARCH_I386_PERCPU__
-#ifndef __ASSEMBLY__
-#include <asm-generic/percpu.h>
-#else
+#ifdef __ASSEMBLY__
+
+/*
+ * PER_CPU finds an address of a per-cpu variable.
+ *
+ * Args:
+ * var - variable name
+ * reg - 32bit register
+ *
+ * The resulting address is stored in the "reg" argument.
+ *
+ * Example:
+ * PER_CPU(cpu_gdt_descr, %ebx)
+ */
+#ifdef CONFIG_SMP
+#define PER_CPU(var, reg) \
+ movl %fs:per_cpu__this_cpu_off, reg; \
+ addl $per_cpu__##var, reg
+#else /* ! SMP */
+#define PER_CPU(var, reg) \
+ movl $per_cpu__##var, reg;
+#endif /* SMP */
+
+#else /* ...!ASSEMBLY */
/*
* PER_CPU finds an address of a per-cpu variable.
@@ -18,14 +39,107 @@
* PER_CPU(cpu_gdt_descr, %ebx)
*/
#ifdef CONFIG_SMP
-#define PER_CPU(var, cpu) \
- movl __per_cpu_offset(,cpu,4), cpu; \
- addl $per_cpu__##var, cpu;
-#else /* ! SMP */
-#define PER_CPU(var, cpu) \
- movl $per_cpu__##var, cpu;
+/* Same as generic implementation except for optimized local access. */
+#define __GENERIC_PER_CPU
+
+/* This is used for other cpus to find our section. */
+extern unsigned long __per_cpu_offset[];
+
+/* Separate out the type, so (int[3], foo) works. */
+#define DECLARE_PER_CPU(type, name) extern __typeof__(type) per_cpu__##name
+#define DEFINE_PER_CPU(type, name) \
+ __attribute__((__section__(".data.percpu"))) __typeof__(type) per_cpu__##name
+
+/* We can use this directly for local CPU (faster). */
+DECLARE_PER_CPU(unsigned long, this_cpu_off);
+
+/* var is in discarded region: offset to particular copy we want */
+#define per_cpu(var, cpu) (*({ \
+ extern int simple_indentifier_##var(void); \
+ RELOC_HIDE(&per_cpu__##var, __per_cpu_offset[cpu]); }))
+
+#define __raw_get_cpu_var(var) (*({ \
+ extern int simple_indentifier_##var(void); \
+ RELOC_HIDE(&per_cpu__##var, x86_read_percpu(this_cpu_off)); \
+}))
+
+#define __get_cpu_var(var) __raw_get_cpu_var(var)
+
+/* A macro to avoid #include hell... */
+#define percpu_modcopy(pcpudst, src, size) \
+do { \
+ unsigned int __i; \
+ for_each_possible_cpu(__i) \
+ memcpy((pcpudst)+__per_cpu_offset[__i], \
+ (src), (size)); \
+} while (0)
+
+#define EXPORT_PER_CPU_SYMBOL(var) EXPORT_SYMBOL(per_cpu__##var)
+#define EXPORT_PER_CPU_SYMBOL_GPL(var) EXPORT_SYMBOL_GPL(per_cpu__##var)
+
+/* fs segment starts at (positive) offset == __per_cpu_offset[cpu] */
+#define __percpu_seg "%%fs:"
+#else /* !SMP */
+#include <asm-generic/percpu.h>
+#define __percpu_seg ""
#endif /* SMP */
+/* For arch-specific code, we can use direct single-insn ops (they
+ * don't give an lvalue though). */
+extern void __bad_percpu_size(void);
+
+#define percpu_to_op(op,var,val) \
+ do { \
+ typedef typeof(var) T__; \
+ if (0) { T__ tmp__; tmp__ = (val); } \
+ switch (sizeof(var)) { \
+ case 1: \
+ asm(op "b %1,"__percpu_seg"%0" \
+ : "+m" (var) \
+ :"ri" ((T__)val)); \
+ break; \
+ case 2: \
+ asm(op "w %1,"__percpu_seg"%0" \
+ : "+m" (var) \
+ :"ri" ((T__)val)); \
+ break; \
+ case 4: \
+ asm(op "l %1,"__percpu_seg"%0" \
+ : "+m" (var) \
+ :"ri" ((T__)val)); \
+ break; \
+ default: __bad_percpu_size(); \
+ } \
+ } while (0)
+
+#define percpu_from_op(op,var) \
+ ({ \
+ typeof(var) ret__; \
+ switch (sizeof(var)) { \
+ case 1: \
+ asm(op "b "__percpu_seg"%1,%0" \
+ : "=r" (ret__) \
+ : "m" (var)); \
+ break; \
+ case 2: \
+ asm(op "w "__percpu_seg"%1,%0" \
+ : "=r" (ret__) \
+ : "m" (var)); \
+ break; \
+ case 4: \
+ asm(op "l "__percpu_seg"%1,%0" \
+ : "=r" (ret__) \
+ : "m" (var)); \
+ break; \
+ default: __bad_percpu_size(); \
+ } \
+ ret__; })
+
+#define x86_read_percpu(var) percpu_from_op("mov", per_cpu__##var)
+#define x86_write_percpu(var,val) percpu_to_op("mov", per_cpu__##var, val)
+#define x86_add_percpu(var,val) percpu_to_op("add", per_cpu__##var, val)
+#define x86_sub_percpu(var,val) percpu_to_op("sub", per_cpu__##var, val)
+#define x86_or_percpu(var,val) percpu_to_op("or", per_cpu__##var, val)
#endif /* !__ASSEMBLY__ */
#endif /* __ARCH_I386_PERCPU__ */
