Re: [Xen-devel] BUG: unable to handle kernel paging request - balloon_init - xen-4.1.0 - 2.6.32.39

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Wed, Apr 27, 2011 at 07:45:42PM -0400, Scott Garron wrote:
> On 04/27/2011 04:09 PM, Konrad Rzeszutek Wilk wrote:
> >Duh! I meant this one:
> >
> >[    0.316665] RIP: e030:[<ffffffff819a8aea>]  [<ffffffff819a8aea>]
> >balloon_init+0x20b/0x25e
> >
> >Sorry about that. Can you also run your kernel with 'initcall_debug
> >loglevel=8' please?
> 
>      Ok, I've put what I came up with here:
> 
> http://www.pridelands.org/~simba/xen-debug/debugnotes.txt
> 
>      I also added a few pr_info() lines around the offending code to try
> to get more of a handle of how far it is getting and what it's working
> on at the time of failure:

This looks quite odd. We had a flurry of issues like these before
were we "forgot" to set the P2M table correctly. So that during
[    0.000000] init_memory_mapping: 0000000100000000-00000001d9ff0000

it would crash b/c for PFNs above the 'dom0_mem' paramater we would
return INVALID value and the machine would crash - but only if the
value was not aligned (git commit f06e457cb729d58430d1385014fab367b2d4e7c2)

But that isn't the case here (dom0_mem=512M).

And you say it boots fine under DomU - so there is some P2M, E820 funkiness
happening here I think. Had you tried booting the kernel as Dom0 with different
sizes of dom0_mem ("dom0_mem=max:2GB?") Or without the dom0_mem parameter at 
all?

What is your CONFIG_XEN_MAX_DOMAIN_MEMORY set to?

> 
> ********
> 
> diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
> index a065fda..b5f0650 100644
> --- a/drivers/xen/balloon.c
> +++ b/drivers/xen/balloon.c
> @@ -488,10 +488,13 @@ static int __init balloon_init(void)
>          */
>         extra_pfn_end = min(min(max_pfn, e820_end_of_ram_pfn()),
>                             (unsigned long)PFN_DOWN(xen_extra_mem_start
> + xen_ex
> +       pr_info("extra_pfn_end: 0x%x", extra_pfn_end); /* debug */
>         for (pfn = PFN_UP(xen_extra_mem_start);
>              pfn < extra_pfn_end;
>              pfn += balloon_npages) {
> +               pr_info("pfn: 0x%x", pfn); /* debug */
>                 page = pfn_to_page(pfn);
> +               pr_info("page: 0x%p", page);  /* debug */
>                 /* totalram_pages doesn't include the boot-time
>                    balloon extension, so don't subtract from it. */
>                 __balloon_append(page);
> 
> 
> ********
> 
>      The new serial console output, with "initcall_debug loglevel=8" and
> the pr_info() additions to the code can be found here:
> 
> http://www.pridelands.org/~simba/xen-debug/hailstorm-fullserial20110427.txt
> 
> ... but I'll paste the part closest to the crash here for your convenience:
> 
> [    1.016663] calling  balloon_init+0x0/0x280 @ 1
> [    1.016663] xen_balloon: Initialising balloon driver with page order 0.
> [    1.033446] last_pfn = 0x1d9ff0 max_arch_pfn = 0x400000000
> [    1.036663] extra_pfn_end: 0x1d9ff0
> [    1.036663] pfn: 0x100000
> [    1.036663] page: 0xffffea0003800000
> [    1.036663] BUG: unable to handle kernel paging request at
> ffffea0003800028
> [    1.036663] IP: [<ffffffff819a8b1f>] balloon_init+0x240/0x280
> [    1.036663] PGD 18402067 PUD 18403067 PMD 0
> 
> 
>      So the crash is happening within the first iteration of that for()
> loop, presumably while calling __balloon_append(page).  That's as far as
> I dove into it so far, but I figured I'd give you an update as to what
> I've found and tried.
> 
>      Just for more information sake, I also tried booting this kernel as
> a paravirt domU under the Debian Stable 2.6.32-5-xen-amd64 stock kernel
> and Xen 4.1.0.  It booted without incident (aside from a ridiculously
> long spew of printk's from my additions to that for() loop), so the
> failure is specific to the kernel booting as a dom0.  That probably
> doesn't narrow down much, but I figured it was noteworthy.
> 
> -- 
> Scott Garron

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