[Xen-bugs] [Bug 1583] New: [RAS] Incorrect behavior after execute first cpu_set command

[bugzilla-daemon@xxxxxxxxxxxxxxxxxxx]

http://bugzilla.xensource.com/bugzilla/show_bug.cgi?id=1583

           Summary: [RAS] Incorrect behavior after execute first cpu_set
                    command
           Product: Xen
           Version: unstable
          Platform: Other
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: Hypervisor
        AssignedTo: xen-bugs@xxxxxxxxxxxxxxxxxxx
        ReportedBy: jiajun.xu@xxxxxxxxx


Environment:
------------
Service Arch (ia32/ia32e/IA64): 
Guest Arch (ia32/ia32e/IA64): 
Guest OS Type (Linux/Windows):
Change Set: 20920:83a6621b91bf
PV Ops dom0:ebeffa31e2016fae9a24664cb90bab2d6d5ce0ab
ioemu:      d463cfee458bacfe1ee3cb9c3b4ce46a6be06edf

Bug detailed description:
--------------------------

When I try to hot-add vcpu to guest OS first time, I always get 2 or 3 CPUs in
guest OS, the expected cpu nr should 1. 

I try to execute offline operation when I use qemu console first time, it
online 2 or CPUs cpu, too.

this issue happens when I execute this first cpu_set command in guest, after
the first command, it works without any problem.


Reproduce steps:
----------------
1. configure maxcpus in guest configure file
2. boot 2.6.30 kernel in guest OS with a minor hack
diff --git a/arch/x86/kernel/apic/probe_64.c b/arch/x86/kernel/apic/probe_64.c
index 1783652..cebf13d 100644
--- a/arch/x86/kernel/apic/probe_64.c
+++ b/arch/x86/kernel/apic/probe_64.c
@@ -64,11 +64,13 @@ void __init default_setup_apic_routing(void)
 #endif

        if (apic == &apic_flat) {
-               if (max_physical_apicid >= 8)
+               if (num_possible_cpus() >= 8)
                        apic = &apic_physflat;
                printk(KERN_INFO "Setting APIC routing to %s\n", apic->name);
        }

+       printk(KERN_INFO "num_possible_cpus: %d\n", num_possible_cpus());
+
        /*
         * Now that apic routing model is selected, configure the
         * fault handling for intr remapping.

and set vcpus = 2, in guest OS
3.execute "cpu_set 2 offline" in guest OS
4. check guest sysfs /sys/device/system/cpu
you will see 4 or 5 cpu entries in this directory


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