[Xen-bugs] [Bug 1687] New: Boot hang because of SIS ACPI bug workaround

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http://bugzilla.xensource.com/bugzilla/show_bug.cgi?id=1687

           Summary: Boot hang because of SIS ACPI bug workaround
           Product: Xen
           Version: unstable
          Platform: x86-64
        OS/Version: Linux-2.6
            Status: NEW
          Severity: normal
          Priority: P2
         Component: Linux-pv_ops dom0
        AssignedTo: xen-bugs@xxxxxxxxxxxxxxxxxxx
        ReportedBy: agrenott@xxxxxxxxx


Trying to switch from xen 3.4.2/2.6.18 to 4.0.1/2.6.32, boot hangs here:

calling  sctp_init+0x0/0x7a8 @ 1
SCTP: Hash tables configured (established 4096 bind 4096)
initcall sctp_init+0x0/0x7a8 returned 0 after 342 usecs
calling  update_mp_table+0x0/0x6be @ 1
initcall update_mp_table+0x0/0x6be returned 0 after 1 usecs
calling  io_apic_bug_finalize+0x0/0x66 @ 1

It's a server in a datacenter where I don't have serial console access, so I
can't give more output (I got these via netconsole module).
However, I've been able to track the issue down to function
io_apic_bug_finalize in arch/x86/kernel/apic/io_apic-xen.c : crash happens when
calling VOID(HYPERVISOR_platform_op(&op));
In my case, it tries to set QUIRK_IOAPIC_BAD_REGSEL.

However, looking at xen 4.0.1 hypervisor source
(xen/arch/x86/platform_hypercall.c), I have:
        case QUIRK_IOAPIC_GOOD_REGSEL:
#ifndef sis_apic_bug
            sis_apic_bug = (quirk_id == QUIRK_IOAPIC_BAD_REGSEL);
            dprintk(XENLOG_INFO, "Domain 0 says that IO-APIC REGSEL is %s\n",
                    sis_apic_bug ? "bad" : "good");
#else
            BUG_ON(sis_apic_bug != (quirk_id == QUIRK_IOAPIC_BAD_REGSEL));
#endif

In my case, sis_apic_bug is defined (meaning work-around is not implemented I
guess), and thus I suppose system hangs because of the BUG_ON.

So it seems to me there's some incompatibility between the dom0 trying to
activate the workaround and the hypervisor refusing it. And indeed, removing
the HYPERVISOR_platform_op call from dom0 allows me to boot.

Please tell me if I need to provide more data.
Rgds,
Aurélien


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