Re: [Xen-devel] guest crash in wrmsr_hypervisor_regs if hypercall page is paged out

[Tim Deegan <tim@xxxxxxx>]

At 20:19 +0200 on 30 Apr (1367353157), Olaf Hering wrote:
> 
> With current xen-unstable I see this guest crash if the gfn 169ff is
> paged out. The xenpaging -v output shows that 169ff is populated, but
> appearently wrmsr_hypervisor_regs does not like the resulting mfn?!

Looks that way:

> (XEN) HVM10: Allocated Xen hypercall page at 169ff000
> (XEN) traps.c:654:d10 Bad GMFN 169ff (MFN 3e900000000) to MSR 40000000

That MFN looks like garbage, so I'm guessing that 'page' was null, i.e.
get_page_from_gfn() returned NULL.  I guess you'll need to instrument it
up to figure out why.  At least the GFN is a predictable constant which
should make it easier to add debugging printout for just this case.

Tim.

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