Re: [PATCH 3/3] KVM: Cache pdptrs

[Avi Kivity <avi@redhat.com>]

Joerg Roedel wrote:
> On Tue, Jun 02, 2009 at 12:09:17PM +0300, Avi Kivity wrote:
>   
>> Joerg Roedel wrote:
>>     
>>> On Mon, Jun 01, 2009 at 04:22:03PM +0300, Avi Kivity wrote:
>>>   
>>>       
>>>> +static void svm_cache_reg(struct kvm_vcpu *vcpu, enum kvm_reg reg)
>>>> +{
>>>> +	switch (reg) {
>>>> +	case VCPU_EXREG_PDPTR:
>>>> +		BUG_ON(!npt_enabled);
>>>> +		load_pdptrs(vcpu, vcpu->arch.cr3);
>>>> +		break;
>>>> +	default:
>>>> +		BUG();
>>>> +	}
>>>> +}
>>>>     
>>>>         
>>> Don't we need to check for the return value of load_pdptrs() here and inject
>>> a #GP it it fails?
>>>   
>>>       
>> We're after some random exit, the guest won't be expecting a #GP in some  
>> random instruction.
>>
>> The only options are ignore and triple fault.
>>     
>
> Thats not different from PAE with NPT anyways. With NPT the hardware
> does not load all four pdptrs on cr3 switch time, only when they
> are used.
>   

That will at least cause a page fault on a related instruction.  But we 
can't #GP on a random exit.

-- 
error compiling committee.c: too many arguments to function