x86-64: Convert irqstacks to per-cpu

Move the irqstackptr variable from the PDA to per-cpu.  Make the
stacks themselves per-cpu, removing some specific allocation code.
Add a seperate flag (is_boot_cpu) to simplify the per-cpu boot
adjustments.

tj: * sprinkle some underbars around.

    * irq_stack_ptr is not used till traps_init(), no reason to
      initialize it early.  On SMP, just leaving it NULL till proper
      initialization in setup_per_cpu_areas() works.  Dropped
      is_boot_cpu and early irq_stack_ptr initialization.

    * do DECLARE/DEFINE_PER_CPU(char[IRQ_STACK_SIZE], irq_stack)
      instead of (char, irq_stack[IRQ_STACK_SIZE]).

Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

5 files changed, 30 insertions, 33 deletions

diff --git a/arch/x86/kernel/asm-offsets_64.c b/arch/x86/kernel/asm-offsets_64.c
index f4cc81bfbf89..5b821fbdaf7b 100644
--- a/arch/x86/kernel/asm-offsets_64.c
+++ b/arch/x86/kernel/asm-offsets_64.c
@@ -54,7 +54,6 @@ int main(void)
         ENTRY(pcurrent); 
         ENTRY(irqcount);
         ENTRY(cpunumber);
-        ENTRY(irqstackptr);
         DEFINE(pda_size, sizeof(struct x8664_pda));
         BLANK();
 #undef ENTRY
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 3d0cc6f17116..496f0a01919b 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -881,7 +881,13 @@ __setup("clearcpuid=", setup_disablecpuid);
 #ifdef CONFIG_X86_64
 struct desc_ptr idt_descr = { 256 * 16 - 1, (unsigned long) idt_table };
 
-static char boot_cpu_stack[IRQSTACKSIZE] __page_aligned_bss;
+DEFINE_PER_CPU_PAGE_ALIGNED(char[IRQ_STACK_SIZE], irq_stack);
+#ifdef CONFIG_SMP
+DEFINE_PER_CPU(char *, irq_stack_ptr);  /* will be set during per cpu init */
+#else
+DEFINE_PER_CPU(char *, irq_stack_ptr) =
+        per_cpu_var(irq_stack) + IRQ_STACK_SIZE - 64;
+#endif
 
 void __cpuinit pda_init(int cpu)
 {
@@ -901,18 +907,7 @@ void __cpuinit pda_init(int cpu)
         if (cpu == 0) {
                 /* others are initialized in smpboot.c */
                 pda->pcurrent = &init_task;
-                pda->irqstackptr = boot_cpu_stack;
-                pda->irqstackptr += IRQSTACKSIZE - 64;
         } else {
-                if (!pda->irqstackptr) {
-                        pda->irqstackptr = (char *)
-                                __get_free_pages(GFP_ATOMIC, IRQSTACK_ORDER);
-                        if (!pda->irqstackptr)
-                                panic("cannot allocate irqstack for cpu %d",
-                                      cpu);
-                        pda->irqstackptr += IRQSTACKSIZE - 64;
-                }
-
                 if (pda->nodenumber == 0 && cpu_to_node(cpu) != NUMA_NO_NODE)
                         pda->nodenumber = cpu_to_node(cpu);
         }
diff --git a/arch/x86/kernel/dumpstack_64.c b/arch/x86/kernel/dumpstack_64.c
index c302d0707048..28e26a4315df 100644
--- a/arch/x86/kernel/dumpstack_64.c
+++ b/arch/x86/kernel/dumpstack_64.c
@@ -106,7 +106,8 @@ void dump_trace(struct task_struct *task, struct pt_regs *regs,
                 const struct stacktrace_ops *ops, void *data)
 {
         const unsigned cpu = get_cpu();
-        unsigned long *irqstack_end = (unsigned long *)cpu_pda(cpu)->irqstackptr;
+        unsigned long *irq_stack_end =
+                (unsigned long *)per_cpu(irq_stack_ptr, cpu);
         unsigned used = 0;
         struct thread_info *tinfo;
         int graph = 0;
@@ -160,23 +161,23 @@ void dump_trace(struct task_struct *task, struct pt_regs *regs,
                         stack = (unsigned long *) estack_end[-2];
                         continue;
                 }
-                if (irqstack_end) {
-                        unsigned long *irqstack;
-                        irqstack = irqstack_end -
-                                (IRQSTACKSIZE - 64) / sizeof(*irqstack);
+                if (irq_stack_end) {
+                        unsigned long *irq_stack;
+                        irq_stack = irq_stack_end -
+                                (IRQ_STACK_SIZE - 64) / sizeof(*irq_stack);
 
-                        if (stack >= irqstack && stack < irqstack_end) {
+                        if (stack >= irq_stack && stack < irq_stack_end) {
                                 if (ops->stack(data, "IRQ") < 0)
                                         break;
                                 bp = print_context_stack(tinfo, stack, bp,
-                                        ops, data, irqstack_end, &graph);
+                                        ops, data, irq_stack_end, &graph);
                                 /*
                                  * We link to the next stack (which would be
                                  * the process stack normally) the last
                                  * pointer (index -1 to end) in the IRQ stack:
                                  */
-                                stack = (unsigned long *) (irqstack_end[-1]);
-                                irqstack_end = NULL;
+                                stack = (unsigned long *) (irq_stack_end[-1]);
+                                irq_stack_end = NULL;
                                 ops->stack(data, "EOI");
                                 continue;
                         }
@@ -199,10 +200,10 @@ show_stack_log_lvl(struct task_struct *task, struct pt_regs *regs,
         unsigned long *stack;
         int i;
         const int cpu = smp_processor_id();
-        unsigned long *irqstack_end =
-                (unsigned long *) (cpu_pda(cpu)->irqstackptr);
-        unsigned long *irqstack =
-                (unsigned long *) (cpu_pda(cpu)->irqstackptr - IRQSTACKSIZE);
+        unsigned long *irq_stack_end =
+                (unsigned long *)(per_cpu(irq_stack_ptr, cpu));
+        unsigned long *irq_stack =
+                (unsigned long *)(per_cpu(irq_stack_ptr, cpu) - IRQ_STACK_SIZE);
 
         /*
          * debugging aid: "show_stack(NULL, NULL);" prints the
@@ -218,9 +219,9 @@ show_stack_log_lvl(struct task_struct *task, struct pt_regs *regs,
 
         stack = sp;
         for (i = 0; i < kstack_depth_to_print; i++) {
-                if (stack >= irqstack && stack <= irqstack_end) {
-                        if (stack == irqstack_end) {
-                                stack = (unsigned long *) (irqstack_end[-1]);
+                if (stack >= irq_stack && stack <= irq_stack_end) {
+                        if (stack == irq_stack_end) {
+                                stack = (unsigned long *) (irq_stack_end[-1]);
                                 printk(" <EOI> ");
                         }
                 } else {
diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index 4833f3a19650..d22677a66438 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -345,7 +345,7 @@ ENTRY(save_args)
 1:      incl %gs:pda_irqcount
         jne 2f
         popq_cfi %rax                   /* move return address... */
-        mov %gs:pda_irqstackptr,%rsp
+        mov PER_CPU_VAR(irq_stack_ptr),%rsp
         EMPTY_FRAME 0
         pushq_cfi %rax                  /* ... to the new stack */
         /*
@@ -1261,7 +1261,7 @@ ENTRY(call_softirq)
         mov  %rsp,%rbp
         CFI_DEF_CFA_REGISTER rbp
         incl %gs:pda_irqcount
-        cmove %gs:pda_irqstackptr,%rsp
+        cmove PER_CPU_VAR(irq_stack_ptr),%rsp
         push  %rbp                      # backlink for old unwinder
         call __do_softirq
         leaveq
@@ -1300,7 +1300,7 @@ ENTRY(xen_do_hypervisor_callback)   # do_hypervisor_callback(struct *pt_regs)
 11:     incl %gs:pda_irqcount
         movq %rsp,%rbp
         CFI_DEF_CFA_REGISTER rbp
-        cmovzq %gs:pda_irqstackptr,%rsp
+        cmovzq PER_CPU_VAR(irq_stack_ptr),%rsp
         pushq %rbp                      # backlink for old unwinder
         call xen_evtchn_do_upcall
         popq %rsp
diff --git a/arch/x86/kernel/setup_percpu.c b/arch/x86/kernel/setup_percpu.c
index b5c35af2011d..8b53ef83c611 100644
--- a/arch/x86/kernel/setup_percpu.c
+++ b/arch/x86/kernel/setup_percpu.c
@@ -192,7 +192,10 @@ void __init setup_per_cpu_areas(void)
 
                 memcpy(ptr, __per_cpu_load, __per_cpu_end - __per_cpu_start);
                 per_cpu_offset(cpu) = ptr - __per_cpu_start;
+                per_cpu(this_cpu_off, cpu) = per_cpu_offset(cpu);
 #ifdef CONFIG_X86_64
+                per_cpu(irq_stack_ptr, cpu) =
+                        (char *)per_cpu(irq_stack, cpu) + IRQ_STACK_SIZE - 64;
                 /*
                  * CPU0 modified pda in the init data area, reload pda
                  * offset for CPU0 and clear the area for others.
@@ -202,7 +205,6 @@ void __init setup_per_cpu_areas(void)
                 else
                         memset(cpu_pda(cpu), 0, sizeof(*cpu_pda(cpu)));
 #endif
-                per_cpu(this_cpu_off, cpu) = per_cpu_offset(cpu);
 
                 DBG("PERCPU: cpu %4d %p\n", cpu, ptr);
         }