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[Xen-devel] Re: machine check report on HVM startup

To: Christoph Egger <Christoph.Egger@xxxxxxx>
Subject: [Xen-devel] Re: machine check report on HVM startup
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Wed, 13 Aug 2008 13:27:15 +0100
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On 13/8/08 12:48, "Christoph Egger" <Christoph.Egger@xxxxxxx> wrote:

> When I launch  memtest as HVM guest, then Xen sends tons of VIRQ_MCA events
> to the Dom0, although there occured NO correctable machine check errors.
> When the Dom0 tries to fetch the error telemetry, then the
> BUG_ON(mc_data.fetch_idx > mc_data.error_idx); in x86_mcinfo_getfetchptr()
> in xen/arch/x86/cpu/mcheck/mce.c is hit. (x86_mcinfo_getfetchptr() only works
> if actually real error occured which is not the case.)

Perhaps you should be more wary of hypercall inputs? Failing the hypercall,
perhaps with a warning printk, would be better than BUG_ON() I think.

> This looks to me, there's a non-public event channel using the same number
> as VIRQ_MCA which fires when  launching memtest as HVM guest.

I don't think this is the case. Sounds easy to repro this issue though. I'll
give it a go.

 -- Keir

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