[PATCH] x86_64: Don't assume BSP has ID 0 in new smp bootup

This patch removes the assumption that LAPIC entries contain the BSP as its
first entry.  This is a slight improvement to the temporary fix submitted by
Suresh Siddha.

- Removes assumption that LAPIC entries contain BSP first.

- Builds x86_acpiid_to_apicid[] and bios_cpu_apicid[] properly with BSP as
  first entry.

- Made maxcpus=1 boot on these systems.  Since the parsing earlier in
  arch/x86_64/kernel/mpparse.c stopped after maxcpus entries, other entries
  were not processed, this causes kernel not to boot on these systems.

TBD: x86_acpiid_to_apicid and bios_cpu_apicid[] seem to be exactly the
     same.  This could be removed, but might need more work to cleanup.

Signed-off-by: Ashok Raj <ashok.raj@intel.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 14 insertions, 8 deletions

diff --git a/arch/x86_64/kernel/mpparse.c b/arch/x86_64/kernel/mpparse.c
index f221231cd0a0..f86d9db94bfc 100644
--- a/arch/x86_64/kernel/mpparse.c
+++ b/arch/x86_64/kernel/mpparse.c
@@ -107,6 +107,7 @@ static int __init mpf_checksum(unsigned char *mp, int len)
 static void __init MP_processor_info (struct mpc_config_processor *m)
 {
         int ver;
+        static int found_bsp=0;
 
         if (!(m->mpc_cpuflag & CPU_ENABLED))
                 return;
@@ -126,11 +127,6 @@ static void __init MP_processor_info (struct mpc_config_processor *m)
                         " Processor ignored.\n", NR_CPUS);
                 return;
         }
-        if (num_processors >= maxcpus) {
-                printk(KERN_WARNING "WARNING: maxcpus limit of %i reached."
-                        " Processor ignored.\n", maxcpus);
-                return;
-        }
 
         num_processors++;
 
@@ -150,7 +146,19 @@ static void __init MP_processor_info (struct mpc_config_processor *m)
                 ver = 0x10;
         }
         apic_version[m->mpc_apicid] = ver;
-        bios_cpu_apicid[num_processors - 1] = m->mpc_apicid;
+        if (m->mpc_cpuflag & CPU_BOOTPROCESSOR) {
+                /*
+                 * bios_cpu_apicid is required to have processors listed
+                 * in same order as logical cpu numbers. Hence the first
+                 * entry is BSP, and so on.
+                 */
+                bios_cpu_apicid[0] = m->mpc_apicid;
+                x86_cpu_to_apicid[0] = m->mpc_apicid;
+                found_bsp = 1;
+        } else {
+                bios_cpu_apicid[num_processors - found_bsp] = m->mpc_apicid;
+                x86_cpu_to_apicid[num_processors - found_bsp] = m->mpc_apicid;
+        }
 }
 
 static void __init MP_bus_info (struct mpc_config_bus *m)
diff --git a/arch/x86_64/kernel/smpboot.c b/arch/x86_64/kernel/smpboot.c
index d00e494c1a39..5abdee1e16a5 100644
--- a/arch/x86_64/kernel/smpboot.c
+++ b/arch/x86_64/kernel/smpboot.c
@@ -645,7 +645,6 @@ static int __cpuinit do_boot_cpu(int cpu, int apicid)
                 printk("failed fork for CPU %d\n", cpu);
                 return PTR_ERR(idle);
         }
-        x86_cpu_to_apicid[cpu] = apicid;
 
         cpu_pda[cpu].pcurrent = idle;
 
@@ -954,7 +953,6 @@ void __cpuinit smp_prepare_cpus(unsigned int max_cpus)
                       GET_APIC_ID(apic_read(APIC_ID)), boot_cpu_id);
                 /* Or can we switch back to PIC here? */
         }
-        x86_cpu_to_apicid[0] = boot_cpu_id;
 
         /*
          * Now start the IO-APICs