linux-kernel - Re: [PATCH v3 1/2] KVM: nVMX: enhance allocate/free

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Message-ID: <BLU436-SMTP999E8310BA48D84AADA728805B0@phx.gbl>
Date:	Wed, 16 Sep 2015 14:51:19 +0800
From:	Wanpeng Li <wanpeng.li@...mail.com>
To:	Jan Kiszka <jan.kiszka@...mens.com>,
	Paolo Bonzini <pbonzini@...hat.com>
CC:	Bandan Das <bsd@...hat.com>, Wincy Van <fanwenyi0529@...il.com>,
	kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/2] KVM: nVMX: enhance allocate/free_vpid to handle
 shadow vpid

On 9/16/15 2:42 PM, Jan Kiszka wrote:
> On 2015-09-16 05:51, Wanpeng Li wrote:
>> Enhance allocate/free_vid to handle shadow vpid.
>>
>> Signed-off-by: Wanpeng Li <wanpeng.li@...mail.com>
>> ---
>>   arch/x86/kvm/vmx.c | 24 +++++++++++-------------
>>   1 file changed, 11 insertions(+), 13 deletions(-)
>>
>> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
>> index 9ff6a3f..4956081 100644
>> --- a/arch/x86/kvm/vmx.c
>> +++ b/arch/x86/kvm/vmx.c
>> @@ -4155,29 +4155,27 @@ static int alloc_identity_pagetable(struct kvm *kvm)
>>   	return r;
>>   }
>>   
>> -static void allocate_vpid(struct vcpu_vmx *vmx)
>> +static int allocate_vpid(void)
>>   {
>> -	int vpid;
>> +	int vpid = 0;
> Initialization is not pointless with the current code.
>
>>   
>> -	vmx->vpid = 0;
>>   	if (!enable_vpid)
>> -		return;
>> +		return 0;
>>   	spin_lock(&vmx_vpid_lock);
>>   	vpid = find_first_zero_bit(vmx_vpid_bitmap, VMX_NR_VPIDS);
>> -	if (vpid < VMX_NR_VPIDS) {
>> -		vmx->vpid = vpid;
>> +	if (vpid < VMX_NR_VPIDS)
>>   		__set_bit(vpid, vmx_vpid_bitmap);
>> -	}
>>   	spin_unlock(&vmx_vpid_lock);
>> +	return vpid;
> You should return 0 also if vpid == VMX_NR_VPIDS.

Agreed.

>
>>   }
>>   
>> -static void free_vpid(struct vcpu_vmx *vmx)
>> +static void free_vpid(int vpid)
>>   {
>>   	if (!enable_vpid)
> You could already test for vpid == 0 here...
>
>>   		return;
>>   	spin_lock(&vmx_vpid_lock);
>> -	if (vmx->vpid != 0)
>> -		__clear_bit(vmx->vpid, vmx_vpid_bitmap);
>> +	if (vpid != 0)
> ...then you could skip this.

Agreed.

>
>> +		__clear_bit(vpid, vmx_vpid_bitmap);
>>   	spin_unlock(&vmx_vpid_lock);
>>   }
>>   
>> @@ -8482,7 +8480,7 @@ static void vmx_free_vcpu(struct kvm_vcpu *vcpu)
>>   
>>   	if (enable_pml)
>>   		vmx_disable_pml(vmx);
>> -	free_vpid(vmx);
>> +	free_vpid(vmx->vpid);
>>   	leave_guest_mode(vcpu);
>>   	vmx_load_vmcs01(vcpu);
>>   	free_nested(vmx);
>> @@ -8501,7 +8499,7 @@ static struct kvm_vcpu *vmx_create_vcpu(struct kvm *kvm, unsigned int id)
>>   	if (!vmx)
>>   		return ERR_PTR(-ENOMEM);
>>   
>> -	allocate_vpid(vmx);
>> +	vmx->vpid = allocate_vpid();
>>   
>>   	err = kvm_vcpu_init(&vmx->vcpu, kvm, id);
>>   	if (err)
>> @@ -8577,7 +8575,7 @@ free_msrs:
>>   uninit_vcpu:
>>   	kvm_vcpu_uninit(&vmx->vcpu);
>>   free_vcpu:
>> -	free_vpid(vmx);
>> +	free_vpid(vmx->vpid);
>>   	kmem_cache_free(kvm_vcpu_cache, vmx);
>>   	return ERR_PTR(err);
>>   }
>>
> Yes, this is what I had in mind.

Thanks for your review. :-)

Regards,
Wanpeng Li
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