Re: [Xen-devel] xen-4.7

[Juergen Gross <jgross@xxxxxxxx>]

On 25/08/16 17:48, Stefan Bader wrote:
> When I try to save a PV guest with 4G of memory using xen-4.7 I get the
> following error:
> 
> II: Guest memory 4096 MB
> II: Saving guest state to file...
> Saving to /tmp/pvguest.save new xl format (info 0x3/0x0/1131)
> xc: info: Saving domain 23, type x86 PV
> xc: error: Bad mfn in p2m_frame_list[0]: Internal error

So the first mfn of the memory containing the p2m information is bogus.
Weird.

> xc: error: mfn 0x4eb1c8, max 0x820000: Internal error
> xc: error:   m2p[0x4eb1c8] = 0xff7c8, max_pfn 0xbffff: Internal error
> xc: error: Save failed (34 = Numerical result out of range): Internal error
> libxl: error: libxl_stream_write.c:355:libxl__xc_domain_save_done: saving
> domain: domain did not respond to suspend request: Numerical result out of 
> range
> Failed to save domain, resuming domain
> xc: error: Dom 23 not suspended: (shutdown 0, reason 255): Internal error
> libxl: error: libxl_dom_suspend.c:460:libxl__domain_resume: xc_domain_resume
> failed for domain 23: Invalid argument
> EE: Guest not off after save!
> FAIL
> 
> From dmesg inside the guest:
> [    0.000000] e820: last_pfn = 0x100000 max_arch_pfn = 0x400000000
> 
> Somehow I am slightly suspicious about
> 
> commit 91e204d37f44913913776d0a89279721694f8b32
>   libxc: try to find last used pfn when migrating
> 
> since that seems to potentially lower ctx->x86_pv.max_pfn which is checked
> against in mfn_in_pseudophysmap(). Is that a known problem?
> With xen-4.6 and the same dom0/guest kernel version combination this does 
> work.

Can you please share some more information? Especially:

- guest kernel version?
- any patches in kernel not being upstream, especially in Xen-specific
  boot path?
- dmesg from guest with E820 map?
- guest configuration?

The same error would occur when trying to live migrate the guest. And
this has been tested a lot since above commit, so I suspect something
is very special in your case.


Juergen

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