linux-kernel - Re: [PATCH v3 7/9] KVM: nSVM: implement nested_svm_load

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Date:   Thu, 9 Jul 2020 19:59:54 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Vitaly Kuznetsov <vkuznets@...hat.com>, kvm@...r.kernel.org
Cc:     Sean Christopherson <sean.j.christopherson@...el.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Junaid Shahid <junaids@...gle.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 7/9] KVM: nSVM: implement nested_svm_load_cr3() and use
 it for host->guest switch

On 09/07/20 19:57, Paolo Bonzini wrote:
> On 09/07/20 16:53, Vitaly Kuznetsov wrote:
>> +	if (nested_npt_enabled(svm))
>> +		nested_svm_init_mmu_context(&svm->vcpu);
>> +
>>  	ret = nested_svm_load_cr3(&svm->vcpu, nested_vmcb->save.cr3,
>>  				  nested_npt_enabled(svm));
> 
> This needs to be done in svm_set_nested_state, so my suggestion is that
> the previous patch includes a call to nested_svm_load_cr3 in
> svm_set_nested_state, and this one adds the "if" inside
> nested_svm_load_cr3 itself.

Actually no, that doesn't work after the next patch.  So the best option
is probably to extract nested_svm_init_mmu as a separate step in
enter_svm_guest_mode.  This also leaves nested_prepare_vmcb_save as a
void function.

Paolo

> 
> Paolo
> 
>> @@ -364,13 +388,6 @@ static int nested_prepare_vmcb_save(struct vcpu_svm *svm, struct vmcb *nested_vm
>>  static void nested_prepare_vmcb_control(struct vcpu_svm *svm)
>>  {
>>  	const u32 mask = V_INTR_MASKING_MASK | V_GIF_ENABLE_MASK | V_GIF_MASK;
>> -	if (nested_npt_enabled(svm))
>> -		nested_svm_init_mmu_context(&svm->vcpu);
>> -
>> -	/* Guest paging mode is active - reset mmu */
>> -	kvm_mmu_reset_context(&svm->vcpu);
>> -
>> -	svm_flush_tlb(&svm->vcpu);
>>  
>