x86: Detect use of extended APIC ID for AMD CPUs

Booting a 32-bit kernel on Magny-Cours results in the following panic:

  ...
  Using APIC driver default
  ...
  Overriding APIC driver with bigsmp
  ...
  Getting VERSION: 80050010
  Getting VERSION: 80050010
  Getting ID: 10000000
  Getting ID: ef000000
  Getting LVT0: 700
  Getting LVT1: 10000
  Kernel panic - not syncing: Boot APIC ID in local APIC unexpected (16 vs 0)
  Pid: 1, comm: swapper Not tainted 2.6.30-rcX #2
  Call Trace:
   [<c05194da>] ? panic+0x38/0xd3
   [<c0743102>] ? native_smp_prepare_cpus+0x259/0x31f
   [<c073b19d>] ? kernel_init+0x3e/0x141
   [<c073b15f>] ? kernel_init+0x0/0x141
   [<c020325f>] ? kernel_thread_helper+0x7/0x10

The reason is that default_get_apic_id handled extension of local APIC
ID field just in case of XAPIC.

Thus for this AMD CPU, default_get_apic_id() returns 0 and
bigsmp_get_apic_id() returns 16 which leads to the respective kernel
panic.

This patch introduces a Linux specific feature flag to indicate
support for extended APIC id (8 bits instead of 4 bits width) and sets
the flag on AMD CPUs if applicable.

Signed-off-by: Andreas Herrmann <andreas.herrmann3@amd.com>
Cc: <stable@kernel.org>
LKML-Reference: <20090608135509.GA12431@alberich.amd.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 1 insertions, 1 deletions

diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h
index 42f2f8377422..9b2c04910e0d 100644
--- a/arch/x86/include/asm/apic.h
+++ b/arch/x86/include/asm/apic.h
@@ -410,7 +410,7 @@ static inline unsigned default_get_apic_id(unsigned long x)
 {
         unsigned int ver = GET_APIC_VERSION(apic_read(APIC_LVR));
 
-        if (APIC_XAPIC(ver))
+        if (APIC_XAPIC(ver) || boot_cpu_has(X86_FEATURE_EXTD_APICID))
                 return (x >> 24) & 0xFF;
         else
                 return (x >> 24) & 0x0F;