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Bug#597828: linux-image-2.6.32-5-amd64: [xen] debug options + sysrq-t => sending NMI to all CPUs: BUG: unable to handle kernel paging request



On Fri, 2010-09-24 at 11:53 -0700, Jeremy Fitzhardinge wrote: 
> On 09/24/2010 01:07 AM, Ian Campbell wrote:
> > NMI injection on 2.6.18 was one of the first Xen things I worked on (for
> > injecting h/w NMI button faults) so something worked once upon a time. I
> > can see CALLBACKTYPE_nmi and VCPUOP_send_nmi which seems promising that
> > it's still around (and extended since I didn't do VCPUOP_send_nmi), even
> > if its bit-rotted or not made it to pvops yet. 
> >
> > In 2.6.18-xen the guest side of receiving an NMI was pretty ugly IIRC
> > since we needed to force a return via the iret hypercall (to allow the
> > hypervisor to simulate the NMI interrupt window).
> >
> > There is a small amount of residual support even in pvops
> > (XEN_EFLAGS_NMI is defined, and tested once on 32 bit, but never set).
> > It might be possible to do something nicer with all the pvops
> > infrastructure, I'm also not sure it isn't a premature optimisation to
> > save a compare by putting the NMI flag into a reserved bit of the saved
> > EFLAGS anyway.
> >
> 
> I think the Intel MCE people have made NMI work in pvops, but I didn't
> look closely.
> 
> But from a pvops perspective, I think the tricky part is sending an NMI
> rather than receiving.

It's not just "HYPERVISOR_vcpu_op(VCPUOP_send_nmi, cpu, NULL)"?

> As I said in my mail to Timo, the simplest option is to disable that code for now.

Agreed.

-- 
Ian Campbell

Your business will assume vast proportions.

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