Re: [PATCH] x86/bugs/multihit: Fix mitigation reporting when KVM is not in use

From: Dave Hansen
Date: Tue Jul 14 2020 - 17:21:07 EST


On 7/14/20 2:04 PM, Pawan Gupta wrote:
>> I see three inputs and four possible states (sorry for the ugly table,
>> it was this or a spreadsheet :):
>>
>> X86_FEATURE_VMX CONFIG_KVM_* hpage split Result Reason
>> N x x Not Affected No VMX
>> Y N x Not affected No KVM
>> Y Y Y Mitigated hpage split
>> Y Y N Vulnerable
> Thank you.
>
> Just a note... for the last 2 cases kernel wont know about "hpage split"
> mitigation until KVM is loaded. So for these cases reporting at boot
> will be "Vulnerable" and would change to "Mitigated" once KVM is loaded
> and deploys the mitigation. This is the current behavior.

That's OK with me, because it's actually pretty closely tied to reality.
You are literally "vulnerable" until you've committed to a mitigation
and that doesn't happen until KVM is loaded.

When are we going to force kvm to be built in, again? ;)