lkml.org 
[lkml]   [2009]   [Jul]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[RFC -tip] x86,apic - set cpu_has_apic for discrete apic
In case of discrete apic (due to hardware or firmware reason)
cpuid may not retrieve cpu_has_apic bit. So for SMP
compiled kernels instead of long check we may set "fake"
cpu_has_apic bit and check only the bit in further code
flow.

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
---

Please review carefully.

arch/x86/kernel/apic/apic.c | 14 ++++++++++++++
1 file changed, 14 insertions(+)

Index: linux-2.6.git/arch/x86/kernel/apic/apic.c
=====================================================================
--- linux-2.6.git.orig/arch/x86/kernel/apic/apic.c
+++ linux-2.6.git/arch/x86/kernel/apic/apic.c
@@ -1003,6 +1003,20 @@ int __init verify_local_APIC(void)
unsigned int reg0, reg1;

/*
+ * For discrete APIC case cpu_has_apic bit could not
+ * be retrieved via cpuid instruction. Same time
+ * we rely on this bit (mostly for SMP compiled
+ * kernel) and instead of checking the long condition
+ * below all the time we do check for plain cpu_has_apic.
+ *
+ * At this moment all the checks are passed and we've
+ * already complained if there was a BIOS bug. This place
+ * should be safe for such a trick. --cvg
+ */
+ if (smp_found_config && !cpu_has_apic && !disable_apic)
+ set_cpu_cap(&boot_cpu_data, X86_FEATURE_APIC);
+
+ /*
* The version register is read-only in a real APIC.
*/
reg0 = apic_read(APIC_LVR);

\
 
 \ /
  Last update: 2009-07-11 23:31    [W:0.039 / U:0.584 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site