Xiaoyao Li <xiaoyao.li@xxxxxxxxx> writes:
> On 3/24/2020 1:02 AM, Thomas Gleixner wrote:
>> Xiaoyao Li <xiaoyao.li@xxxxxxxxx> writes:
>>
>>> Current initialization flow of split lock detection has following issues:
>>> 1. It assumes the initial value of MSR_TEST_CTRL.SPLIT_LOCK_DETECT to be
>>> zero. However, it's possible that BIOS/firmware has set it.
>>
>> Ok.
>>
>>> 2. X86_FEATURE_SPLIT_LOCK_DETECT flag is unconditionally set even if
>>> there is a virtualization flaw that FMS indicates the existence while
>>> it's actually not supported.
>>>
>>> 3. Because of #2, KVM cannot rely on X86_FEATURE_SPLIT_LOCK_DETECT flag
>>> to check verify if feature does exist, so cannot expose it to
>>> guest.
>>
>> Sorry this does not make anny sense. KVM is the hypervisor, so it better
>> can rely on the detect flag. Unless you talk about nested virt and a
>> broken L1 hypervisor.
>>
>
> Yeah. It is for the nested virt on a broken L1 hypervisor.
Then please spell it out in the changelog. Changelogs which need crystalballs
to decode are pretty useless.
Thanks,
tglx
