Re: [Xen-devel] [PATCH RFC 0/1] Introduce VCPUOP_reset_vcpu_info

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Wed, Aug 06, 2014 at 03:54:57PM +0100, Jan Beulich wrote:
> >>> On 06.08.14 at 16:49, <konrad.wilk@xxxxxxxxxx> wrote:
> > On Wed, Aug 06, 2014 at 03:09:43PM +0100, Jan Beulich wrote:
> >> Just for my understanding of why exactly you need the new operation:
> >> Why is this being done here, when you already do the reset in the
> >> cpu-die/shutdown paths? And why not for CPU 0?
> >> 
> >> Furthermore, what is the state of vCPU-s beyond 31 going to be after
> >> they got their vCPU info reset? They won't have any other area as
> >> fallback. Yet I don't think you can now and forever guarantee that
> >> native_cpu_die() won't do anything requiring that structure.
> > 
> > native_cpu_die just spins around in an infinite halt sequence. The
> > call could be replaced with the VCPU_down call instead, something like:
> > 
> >     if (xen_teardown_cpu(cpu) == -ENOSYS)
> >             native_cpu_die();
> >     
> >     (void)HYPERVISOR_vcpu_op(VCPUP_down, cpu, NULL);
> 
> But the suggested new hypercall requires the vCPU to be down in
> order to allow the reset...

Duh! I wrote it and I should have remember that :-) It is RFC for a reason!
> 
> Jan
> 

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