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

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Message-ID: <f4985baa-1694-775f-6a17-4759ad760a87@gmail.com>
Date:	Wed, 13 Jul 2016 18:02:46 +0800
From:	Yang Zhang <yang.zhang.wz@...il.com>
To:	Paolo Bonzini <pbonzini@...hat.com>, linux-kernel@...r.kernel.org,
	kvm@...r.kernel.org
Subject: Re: [RFC PATCH 4/4] KVM: vmx: add support for emulating UMIP

On 2016/7/13 17:35, Paolo Bonzini wrote:
>
>
> 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))".

Sorry, I consider it under my previous suggestion(setting it 
unconditionally). :(

-- 
Yang
Alibaba Cloud Computing