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Date: Tue, 14 Sep 2010 04:29:54 -0400 (EDT)
From: CAI Qian <caiqian@redhat.com>
To: Tejun Heo <tj@kernel.org>
Cc: linux-kernel <linux-kernel@vger.kernel.org>, Avi Kivity <avi@redhat.com>,
        Marcelo Tosatti <mtosatti@redhat.com>, dhowells@redhat.com,
        graff yang <graff.yang@gmail.com>, sonic adi <sonic.adi@gmail.com>,
        kexec <kexec@lists.infradead.org>,
        Chris Lalancette <clalance@redhat.com>
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Subject: Re: kvm kdump regression
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----- "Tejun Heo" <tj@kernel.org> wrote:

> On 09/14/2010 05:09 AM, CAI Qian wrote:
> > This commit introduced a regression that an empty vmcore was
> generated on a kvm guest.
> > ioremap: invalid physical address db74000000000000
> > ------------[ cut here ]------------
> > WARNING: at arch/x86/mm/ioremap.c:83 __ioremap_caller+0x307/0x380()
> > Hardware name: KVM
> > Modules linked in:
> > Pid: 1, comm: swapper Not tainted 2.6.36-rc2-mm1+ #2
> > Call Trace:
> >  [<ffffffff8105f48f>] warn_slowpath_common+0x7f/0xc0
> >  [<ffffffff8103052e>] ? copy_oldmem_page+0x4e/0xc0
> >  [<ffffffff8105f4ea>] warn_slowpath_null+0x1a/0x20
> >  [<ffffffff8103f0a7>] __ioremap_caller+0x307/0x380
> >  [<ffffffff8103f1f7>] ioremap_nocache+0x17/0x20
> >  [<ffffffff8103052e>] copy_oldmem_page+0x4e/0xc0
> >  [<ffffffff811af4ca>] read_from_oldmem+0x7a/0xb0
> >  [<ffffffff81c4f70b>] merge_note_headers_elf64.clone.1+0x6c/0x21f
> >  [<ffffffff8103056e>] ? copy_oldmem_page+0x8e/0xc0
> >  [<ffffffff811af4ca>] ? read_from_oldmem+0x7a/0xb0
> >  [<ffffffff81c4fa5b>] vmcore_init+0x19d/0x396
> >  [<ffffffff81c4f8be>] ? vmcore_init+0x0/0x396
> >  [<ffffffff81002053>] do_one_initcall+0x43/0x190
> >  [<ffffffff81c278ab>] kernel_init+0x2a0/0x330
> >  [<ffffffff8100be84>] kernel_thread_helper+0x4/0x10
> >  [<ffffffff81c2760b>] ? kernel_init+0x0/0x330
> >  [<ffffffff8100be80>] ? kernel_thread_helper+0x0/0x10
> > ---[ end trace 93d72a36b9146f22 ]---
> > Kdump: vmcore not initialized
> > 
> > commit 020ec6537aa65c18e9084c568d7b94727f2026fd
> > Author: Tejun Heo <tj@kernel.org>
> > Date:   Fri Apr 9 18:57:00 2010 +0900
> > 
> >     percpu: factor out pcpu_addr_in_first/reserved_chunk() and
> update per_cpu_ptr_to_phys()
> 
> Hmm... I'm confused.  Isn't this the one fixed by commit 9983b6f0
> (percpu: fix first chunk match in per_cpu_ptr_to_phys())?
No, it did not. 2.6.36-rc2-mm1 still had the same problem.
> 
> Thanks.
> 
> -- 
> tejun