Messages in this thread | | | Subject | Re: [PATCH v5 1/9] x86/split_lock: Rework the initialization flow of split lock detection | From | Xiaoyao Li <> | Date | Tue, 24 Mar 2020 19:51:19 +0800 |
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On 3/24/2020 1:02 AM, Thomas Gleixner wrote: > Xiaoyao Li <xiaoyao.li@intel.com> 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.
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