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

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> 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...

Jan


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