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    DateSun, 24 Feb 2008 13:29:03 +0100
    FromAndi Kleen <>
    SubjectRe: [PATCH] x86_64: make amd quad core 8 socket system not be clustered_box v2
    On Sat, Feb 23, 2008 at 09:48:42PM -0800, Yinghai Lu wrote:
    > 
    > quad core 8 socket system will have apic id lifting.the apic id range could
    > be [4, 0x23]. and apic_is_clustered_box will think that need to three clusters
    > and that is large than 2. So it is treated as clustered_box.
    
    Ok I see you chose the quick hack over doing it properly ...
    
    > 
    > and will get
    > 
    > Marking TSC unstable due to TSCs unsynchronized
    > 
    > even the CPUs have X86_FEATURE_CONSTANT_TSC set.
    
    I doubt that will do the right thing on AMD based vSMP,
    which also required the cluster check on AMD iirc.
    
    Cc'ed Kiran/Shai. damage has already hit x86 tree I believe.
    
    -Andi
    
    diff --git a/arch/x86/kernel/apic_64.c b/arch/x86/kernel/apic_64.c
    index d8d03e0..7d8ffda 100644
    --- a/arch/x86/kernel/apic_64.c
    +++ b/arch/x86/kernel/apic_64.c
    @@ -1180,9 +1180,19 @@ __cpuinit int apic_is_clustered_box(void)
     {
            int i, clusters, zeros;
            unsigned id;
    -       u16 *bios_cpu_apicid = x86_bios_cpu_apicid_early_ptr;
    +       u16 *bios_cpu_apicid;
            DECLARE_BITMAP(clustermap, NUM_APIC_CLUSTERS);
    +       /*
    +        * Some AMD box with quadcore cpu and 8 sockets apicid
    +        * will be [4, 0x23] or [8, 0x27] could be thought to
    +        * have three apic_clusters. So go out early.
    +        */
    +       if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD)
    +               return 0;
    
    --
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