From mboxrd@z Thu Jan  1 00:00:00 1970
From: Marcelo Tosatti <mtosatti@redhat.com>
Subject: Re: 2.6.29-rc3 oops with kvmclock
Date: Sun, 8 Feb 2009 04:02:13 -0200
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To: Mark McLoughlin <markmc@redhat.com>
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Hi Mark,

On Tue, Feb 03, 2009 at 10:25:27AM +0000, Mark McLoughlin wrote:
> Hi,
> 
> Same guest, this time a kvmclock related oops.
> 
> Cheers,
> Mark.
> 
> kernel BUG at include/linux/mm.h:302!

static inline void get_page(struct page *page)
{
        page = compound_head(page);
        VM_BUG_ON(atomic_read(&page->_count) == 0);
        atomic_inc(&page->_count);
}

> RIP  [<ffffffff810bb332>] do_wp_page+0x324/0x6d8

>>From do_wp_page (COW pagefault handler). So the page was freed (or
thats how do_wp_page perceives it) while expected not to be (probably
because the page is pinned by the read-only pte reference, by the time
do_wp_page starts).

> invalid opcode: 0000 [#1] SMP DEBUG_PAGEALLOC

The FC11 kernel has pvmmu on. It _could_ be a weird side effect of the
pvmmu slab bug (which only happens with DEBUG_PAGEALLOC). What were you
doing when this happened? Reproducible?

Or some other corruption that causes the crazy symptom.