[Xen-users] Dom0 hangs on boot, CentOS 5 x86_64

[Steve Hill <steve@xxxxxxxxxxx>]

I have been trying to get Xen working on an Intel S5000VLC motherboard in 
x86_64 mode running CentOS 5 (2.6.18 kernel).  It boots fine without Xen, 
but when running Xen I get a hang on boot while it is configuring the PCI 
devices.  I've done some debugging, and it appears that the problem is a 
HYPERVISOR_physdev_op() call, which never returns.

The call at fault is in io_apic_write() in arch/x86_64/kernel/io_apic-xen.c:
        HYPERVISOR_physdev_op(PHYSDEVOP_apic_write, &apic_op);
which is called from io_apic_set_pci_routing() (in the same file):
        io_apic_write(ioapic, 0x10+2*pin, *(((int *)&entry)+0));
called from mp_register_gsi() in arch/x86_64/kernel/mpparse-xen.c:
        io_apic_set_pci_routing(ioapic, ioapic_pin, gsi, triggering ==
                ACPI_EDGE_SENSITIVE ? 0 : 1, polarity == ACPI_ACTIVE_HIGH
                 ? 0 : 1);
called from acpi_register_gsi() in arch/i386/kernel/acpi/boot-xen.c:
        plat_gsi = mp_register_gsi(gsi, triggering, polarity);

I lost track of the calls at this point, but picked them up again in 
arch/i386/pci/common.c where pcibios_enable_device() calls:
        return pcibios_enable_irq(dev);
which is called from pci_enable_device_bars() in drivers/pci/pci.c:
        err = pcibios_enable_device(dev, bars);
called from pci_enable_device() in the same file:
        err = pci_enable_device_bars(dev, (1 << PCI_NUM_RESOURCES) - 1);
called from drivers/pci/bus.c:
        retval = pci_enable_device(dev);


The problem also happens under Fedora 7 when running Xen.

It looks like something might not be getting initialised, since the xen 
kernel boots fine if you boot the non-xen kernel first and then reboot 
without powering off in between.
The motherboard is running the latest (2 month old) BIOS, however I've 
noticed that the stock (non-Xen) Fedora 7 kernel fails to boot unless you 
specify acpi=off, so presumably the BIOS has some ACPI bugs.  Specifying 
acpi=off doesn't solve the Xen problem though.
I'd appreciate any suggestions.  I'm relatively happy poking around in 
the Linux kernel, but since it is a call to the Xen hypervisor which is 
hanging I'm a bit stumped, having never looked at the Xen sourcecode 
before.
Thank you.

--

 - Steve
   xmpp:steve@xxxxxxxxxxx   sip:steve@xxxxxxxxxxx   http://www.nexusuk.org/

     Servatis a periculum, servatis a maleficum - Whisper, Evanescence


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