Re: [RFC PATCH 4/4] KVM: vmx: add support for emulating UMIP

[Paolo Bonzini]

On 13/07/2016 11:21, Yang Zhang wrote:
>>
>> +static int handle_desc(struct kvm_vcpu *vcpu)
>> +{
>> +    WARN_ON(!(vcpu->arch.cr4 & X86_CR4_UMIP));
> 
> I think WARN_ON is too heavy since a malicious guest may trigger it always.

I missed this---how so?  Setting the bit is under "if ((cr4 &
X86_CR4_UMIP) && !boot_cpu_has(X86_FEATURE_UMIP))".

Paolo