x86: fold pda into percpu area on SMP

[ Based on original patch from Christoph Lameter and Mike Travis. ]

Currently pdas and percpu areas are allocated separately.  %gs points
to local pda and percpu area can be reached using pda->data_offset.
This patch folds pda into percpu area.

Due to strange gcc requirement, pda needs to be at the beginning of
the percpu area so that pda->stack_canary is at %gs:40.  To achieve
this, a new percpu output section macro - PERCPU_VADDR_PREALLOC() - is
added and used to reserve pda sized chunk at the start of the percpu
area.

After this change, for boot cpu, %gs first points to pda in the
data.init area and later during setup_per_cpu_areas() gets updated to
point to the actual pda.  This means that setup_per_cpu_areas() need
to reload %gs for CPU0 while clearing pda area for other cpus as cpu0
already has modified it when control reaches setup_per_cpu_areas().

This patch also removes now unnecessary get_local_pda() and its call
sites.

A lot of this patch is taken from Mike Travis' "x86_64: Fold pda into
per cpu area" patch.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 1 insertions, 59 deletions

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 70d846628bbf..f2f77ca494d4 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -744,52 +744,6 @@ static void __cpuinit do_fork_idle(struct work_struct *work)
         complete(&c_idle->done);
 }
 
-#ifdef CONFIG_X86_64
-
-/* __ref because it's safe to call free_bootmem when after_bootmem == 0. */
-static void __ref free_bootmem_pda(struct x8664_pda *oldpda)
-{
-        if (!after_bootmem)
-                free_bootmem((unsigned long)oldpda, sizeof(*oldpda));
-}
-
-/*
- * Allocate node local memory for the AP pda.
- *
- * Must be called after the _cpu_pda pointer table is initialized.
- */
-int __cpuinit get_local_pda(int cpu)
-{
-        struct x8664_pda *oldpda, *newpda;
-        unsigned long size = sizeof(struct x8664_pda);
-        int node = cpu_to_node(cpu);
-
-        if (cpu_pda(cpu) && !cpu_pda(cpu)->in_bootmem)
-                return 0;
-
-        oldpda = cpu_pda(cpu);
-        newpda = kmalloc_node(size, GFP_ATOMIC, node);
-        if (!newpda) {
-                printk(KERN_ERR "Could not allocate node local PDA "
-                        "for CPU %d on node %d\n", cpu, node);
-
-                if (oldpda)
-                        return 0;       /* have a usable pda */
-                else
-                        return -1;
-        }
-
-        if (oldpda) {
-                memcpy(newpda, oldpda, size);
-                free_bootmem_pda(oldpda);
-        }
-
-        newpda->in_bootmem = 0;
-        cpu_pda(cpu) = newpda;
-        return 0;
-}
-#endif /* CONFIG_X86_64 */
-
 static int __cpuinit do_boot_cpu(int apicid, int cpu)
 /*
  * NOTE - on most systems this is a PHYSICAL apic ID, but on multiquad
@@ -807,16 +761,6 @@ static int __cpuinit do_boot_cpu(int apicid, int cpu)
         };
         INIT_WORK(&c_idle.work, do_fork_idle);
 
-#ifdef CONFIG_X86_64
-        /* Allocate node local memory for AP pdas */
-        if (cpu > 0) {
-                boot_error = get_local_pda(cpu);
-                if (boot_error)
-                        goto restore_state;
-                        /* if can't get pda memory, can't start cpu */
-        }
-#endif
-
         alternatives_smp_switch(1);
 
         c_idle.idle = get_idle_for_cpu(cpu);
@@ -931,9 +875,7 @@ do_rest:
                                 inquire_remote_apic(apicid);
                 }
         }
-#ifdef CONFIG_X86_64
-restore_state:
-#endif
+
         if (boot_error) {
                 /* Try to put things back the way they were before ... */
                 numa_remove_cpu(cpu); /* was set by numa_add_cpu */