linux-kernel - RE: BUG: 2.6.30.1 pv_ops kernel boot failure

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Message-ID: <683099EDC3E36D40942EBF636EB88BF00701E3D6@batmail1.corp.amdocs.com>
Date:	Tue, 25 Aug 2009 13:53:21 +0100
From:	"James Dingwall" <james.dingwall@...ocs.com>
To:	"Andreas Herrmann" <andreas.herrmann3@....com>
Cc:	<linux-kernel@...r.kernel.org>
Subject: RE: BUG: 2.6.30.1 pv_ops kernel boot failure - bisected


> On Tue, Aug 25, 2009 at 12:04:54PM +0100, James Dingwall wrote:
> >
> > Hi,
> >
> > I have encountered what appears to be a bug when using the 2.6.30
> stable
> > series as a pv_ops kernel under Xen 3.4.1.  The problem appears to
> have
> > been introduced with the following commit (provided I bisected it
> > correctly)
> >
> > commit bb9b409349f533a919b6b6d95698fbe6ff4aa209
> > Author: Andreas Herrmann <andreas.herrmann3@....com>
> > Date:   Mon Jun 8 15:55:09 2009 +0200
> >
> >     x86: Detect use of extended APIC ID for AMD CPUs
> >
> > When I try and boot the domU (xm create -c) I do not get any output.
> > With this commit reverted I can boot 2.6.30.5 pv_ops without issue,
> > output follows below.  The system is a dual Opteron 242.  If more
> > details about the hardware or configuration are required to debug
> this
> > please let me know.  I'm willing to test any patches.
> 
> 
> So it seems that commit
> 
>  commit 2cb078603abb612e3bcd428fb8122c3d39e08832
>  Author: Jeremy Fitzhardinge <jeremy@...p.org>
>  Date:   Wed Jul 22 09:59:35 2009 -0700
> 
>     x86, amd: Don't probe for extended APIC ID if APICs are disabled
> 
>     If we've logically disabled apics, don't probe the PCI space for
> the
>     AMD extended APIC ID.
> 
>     [ Impact: prevent boot crash under Xen. ]
> 
>     Signed-off-by: Jeremy Fitzhardinge
<jeremy.fitzhardinge@...rix.com>
>     Reported-by: Bastian Blank <bastian@...di.eu.org>
>     Signed-off-by: H. Peter Anvin <hpa@...or.com>
> 
> needs to be added to 2.6.30.y for proper boot under Xen.
> James, can you test this please?

Hi Andreas,

That commit won't apply directly on top of 2.6.30.5 as the #ifdef which
contains it is missing.  However, based on what you suggested I have the
following patch below which resolves the problem for me.  Here's hoping
it doesn't get munged by my mailer...

James

diff --git a/arch/x86/include/asm/cpufeature.h
b/arch/x86/include/asm/cpufeature.h
index bb83b1c..2f5ebf1 100644
--- a/arch/x86/include/asm/cpufeature.h
+++ b/arch/x86/include/asm/cpufeature.h
@@ -94,6 +94,7 @@
 #define X86_FEATURE_TSC_RELIABLE (3*32+23) /* TSC is known to be
reliable */
 #define X86_FEATURE_NONSTOP_TSC        (3*32+24) /* TSC does not stop
in C states */
 #define X86_FEATURE_CLFLUSH_MONITOR (3*32+25) /* "" clflush reqd with
monitor */
+#define X86_FEATURE_EXTD_APICID (3*32+26) /* has extended APICID (8
bits) */

 /* Intel-defined CPU features, CPUID level 0x00000001 (ecx), word 4 */
 #define X86_FEATURE_XMM3       (4*32+ 0) /* "pni" SSE-3 */
diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index 0a9092f..61a592e 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -6,6 +6,7 @@
 #include <asm/processor.h>
 #include <asm/apic.h>
 #include <asm/cpu.h>
+#include <asm/pci-direct.h>

 #ifdef CONFIG_X86_64
 # include <asm/numa_64.h>
@@ -353,6 +354,15 @@ static void __cpuinit early_init_amd(struct
cpuinfo_x86 *c)
                    (c->x86_model == 8 && c->x86_mask >= 8))
                        set_cpu_cap(c, X86_FEATURE_K6_MTRR);
 #endif
+#if defined(CONFIG_X86_LOCAL_APIC) && defined(CONFIG_PCI)
+       /* check CPU config space for extended APIC ID */
+       if (cpu_has_apic && c->x86 >= 0xf) {
+               unsigned int val;
+               val = read_pci_config(0, 24, 0, 0x68);
+               if ((val & ((1 << 17) | (1 << 18))) == ((1 << 17) | (1
<< 18)))
+                       set_cpu_cap(c, X86_FEATURE_EXTD_APICID);
+       }
+#endif
 }

 static void __cpuinit init_amd(struct cpuinfo_x86 *c)



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