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[Xen-devel] Re: apic probe of pv linux

To: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Subject: [Xen-devel] Re: apic probe of pv linux
From: Jiageng Yu <yujiageng734@xxxxxxxxx>
Date: Sat, 28 May 2011 12:56:28 +0800
Cc: "Xen-devel@xxxxxxxxxxxxxxxxxxx" <Xen-devel@xxxxxxxxxxxxxxxxxxx>, Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>, Stefano Stabellini <Stefano.Stabellini@xxxxxxxxxxxxx>
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2011/5/28 Jeremy Fitzhardinge <jeremy@xxxxxxxx>:
> On 05/27/2011 02:29 AM, Jiageng Yu wrote:
>> I have updated the pv linux kernel from to I
>> found the generic_apic_probe always led to a kernel panic when I try
>> to make the minimal DomU kernel.
>> The pv linux use the new apic probe mechanism:
>> static __init int xen_safe_probe(void) {
>>       if (!xen_initial_domain())
>>               return 0;
>>       return 1;
>> }
>> #ifdef CONFIG_XEN_DOM0
>> #define xen_initial_domain()  (xen_pv_domain() && xen_start_info->flags
>> #else  /* !CONFIG_XEN_DOM0 */
>> #define xen_initial_domain()  (0)
>> #endif        /* CONFIG_XEN_DOM0 */
>> If do not define the CONFIG_XEN_DOM0, xen_safe_probe will always
>> return 0 which causes the kernel panic. For the minimal DomU kernel,
>> the CONFIG_XEN_DOM0 is needless, and in this scenario, how to pass the
>> apic probe safely?
> Thanks for looking into this.  In theory a minimal domU kernel should
> never have anything to do with APICs, since there are none present in a
> PV domain.  Do you have a stack backtrace for when it crashes?
> Thanks,
>    J

Thanks, Jeremy. This is the panic output when starting the domU kernel:
<0>Kernel panic - not syncing: Didn't find an APIC driver
Pid: 0, comm: swapper Not tainted #1
Call Trace:
 [<c0123406>] ? panic+0x46/0x100
 [<c032a08d>] ? generic_apic_probe+0x6d/0x70
 [<c03220eb>] ? xen_pagetable_setup_done+0x6b/0x70
 [<c0323533>] ? setup_arch+0x483/0x
 [<c020305b>] ? dom0_write_console+0x1b/0x40990
 [<c0124077>] ? printk+0x47/0x60
 [<c031f67b>] ?  start_kernel+0x6b/0x2d0
 [<c0321516>] ? xen_start_kernel+0x396/0x3d0

For debugging perpose, I insert xen_raw_console_write into printk, and
the dom0_write_console belongs to xen_raw_console_write function.

My config file is:
kernel = "/root/xen-unstable.hg/linux-stubdom/vmlinuz-ioemu"
ramdisk = "/root/xen-unstable.hg/linux-stubdom/ramdisk-ioemu"
memory = 32

The domU kernel config file is attached. I have cut the options about
backend drivers, dom0, and privileged_guest. So, there is no
CONFIG_XEN_DOM0 option when starting the domU kernel.


Attachment: linux-config-ioemu
Description: Binary data

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