x86, trampoline: Common infrastructure for low memory trampolines

Common infrastructure for low memory trampolines.  This code installs
the trampolines permanently in low memory very early.  It also permits
multiple pieces of code to be used for this purpose.

This code also introduces a standard infrastructure for computing
symbol addresses in the trampoline code.

The only change to the actual SMP trampolines themselves is that the
64-bit trampoline has been made reusable -- the previous version would
overwrite the code with a status variable; this moves the status
variable to a separate location.

Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
LKML-Reference: <4D5DFBE4.7090104@intel.com>
Cc: Rafael J. Wysocki <rjw@sisk.pl>
Cc: Matthieu Castet <castet.matthieu@free.fr>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>

1 files changed, 6 insertions, 4 deletions

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 08776a953487..545273369efa 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -788,7 +788,7 @@ do_rest:
         stack_start  = c_idle.idle->thread.sp;
 
         /* start_ip had better be page-aligned! */
-        start_ip = setup_trampoline();
+        start_ip = trampoline_address();
 
         /* So we see what's up */
         announce_cpu(cpu, apicid);
@@ -798,6 +798,8 @@ do_rest:
          * the targeted processor.
          */
 
+        printk(KERN_DEBUG "smpboot cpu %d: start_ip = %lx\n", cpu, start_ip);
+
         atomic_set(&init_deasserted, 0);
 
         if (get_uv_system_type() != UV_NON_UNIQUE_APIC) {
@@ -851,8 +853,8 @@ do_rest:
                         pr_debug("CPU%d: has booted.\n", cpu);
                 else {
                         boot_error = 1;
-                        if (*((volatile unsigned char *)trampoline_base)
-                                        == 0xA5)
+                        if (*(volatile u32 *)TRAMPOLINE_SYM(trampoline_status)
+                            == 0xA5A5A5A5)
                                 /* trampoline started but...? */
                                 pr_err("CPU%d: Stuck ??\n", cpu);
                         else
@@ -878,7 +880,7 @@ do_rest:
         }
 
         /* mark "stuck" area as not stuck */
-        *((volatile unsigned long *)trampoline_base) = 0;
+        *(volatile u32 *)TRAMPOLINE_SYM(trampoline_status) = 0;
 
         if (get_uv_system_type() != UV_NON_UNIQUE_APIC) {
                 /*