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Re: [Xen-devel] [PATCH 0/2] extract vmcoreinfo from /proc/vmcore for Xen


The aim of "vmcoreinfo in vmcore" is to run makedumpfile
without xen-syms.

The basic form of the xen extraction:
# makedumpfile -X --xen-syms xen-syms /proc/vmcore output-file
It selects pages owned by the hypervisor and the domain 0 and
makes a size reduced vmcore image.
The page selection is done as follows:
- scan alloc_bitmap and frametable
  - select if alloc_bitmap on &&
    - xen heap
    - owned by dom0/dom-xen/dom-io
The necessary infomation such as the symbol address of alloc_bitmap,
the size of page_info, the offset of _domain in page_info, and so on
are extracted in the xen-syms.

The vmcoreinfo is a note section in a vmcore which is packed the
infomation neccessary for page selection. If a vmcoreinfo exists
in a vmcore, xen-syms is not necessary to run makedumpfile:
# makedumpfile -X /proc/vmcore output-file
does the same thing as mentioned above.

Itsuro Oda

On Thu, 12 Jun 2008 15:36:33 +0100
Keir Fraser <keir.fraser@xxxxxxxxxxxxx> wrote:

> I'm a bit confused as to what this is for. If you know where Xen is located
> in physical or virtual address space, and you have access to Xen symbols,
> why would you need the few symbol addresses provided by vmcoreinfo? I can
> hardly see what symbols dom_xen and dom_io would be particularly useful for.
> Similarly, why would you record structure sizes when this is statically
> determinable given the Xen sources?
>  -- Keir
> On 12/6/08 09:22, "Itsuro ODA" <oda@xxxxxxxxxxxxx> wrote:
> > Hi,
> > 
> > The following patchset is to support extracting vmcoreinfo from
> > /proc/vmcore for Xen.
> > 
> > This is the up-port of the patchset I made for 3.2.0 and posted
> > the end of March.
> > 
> > [PATCH 1/2] patch for xen hypervisor (xen-unstable.hg)
> > [PATCH 2/2] patch for linux (linux-2.6.18-xen.hg)
> > 
> > --- background ----------------------------------------------------
> > * what the makedumpfile is:
> >   To shorten the size of the dumpfile and the time of creating the
> >   dumpfile, makedumpfile copies only the necessary pages for analysis
> >   to the dumpfile from /proc/vmcore. You can specify the kind of
> >   unnecessary pages with dump_level. If you want to shorten the size
> >   further, enable the compression of the page data.
> > * Xen extraction 
> >   makedumpfile also has a feature that extracting the part of
> >   xen hypervisor and domain-0 from /proc/vmcore taken under xen
> >   environment. In most cases under xen environment, it is enough to
> >   analyze a cause of system crash.
> > * extract vmcoreinfo from /proc/vmcore
> >   makedumpfile 1.2.0 supports to extract the vmcoreinfo data from
> >   /proc/vmcore and uses it for dump filtering. (for a vmcore taken
> >   under the native environment.)
> > ------------------------------------------------------------------
> > 
> > Thanks.

Itsuro ODA <oda@xxxxxxxxxxxxx>

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