[PATCH] KVM: arm64: fix MPIDR to vcpu index cache to support vcpu change at runtime

[liting (Q)]

On 2023/11/30 3:18, Marc Zyngier wrote:
> On Tue, 28 Nov 2023 13:54:02 +0000,
> l00313349 <liting8 at huawei.com> wrote:
>> From: Ting Li <liting8 at huawei.com>
>>
>> Consider vcpu change at runtime, for example online_vcpus is 8,
>> but only start 2 vcpu threads, MPIDR to vcpu index 0 may be overwrited
>> and vm hangs. When start other vcpu threads, cache will be outdated
>> and always get mismatch.
> If userspace creates two vcpus with the same vcpu_id, and therefore
> the same MPIDR value, that's userspace's problem. Don't do that.
>
> Why should we do anything else?
>
> 	M.
Hi Marc,
Thanks for your reply. Maybe you have misunderstanding about it.
The problem is not two vcpus with the same vcpu_id, but different vcpu_id
have the same MPIDR value in some situation such as vcpu hotplug.
In my case, total vcpu count is 8 but only start 2 vcpu at the beginning,
then vcpu_id 2-7 will get the same MPIDR value 0 with vcpu_id 0, so
index 0 will be overwrited to vcpu_id 7.
Please check, thanks.
Ting Li