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

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Message-ID: <55F90F6E.6070002@siemens.com>
Date:	Wed, 16 Sep 2015 08:42:54 +0200
From:	Jan Kiszka <jan.kiszka@...mens.com>
To:	Wanpeng Li <wanpeng.li@...mail.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 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.

>  }
>  
> -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.

> +		__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.

Jan

-- 
Siemens AG, Corporate Technology, CT RTC ITP SES-DE
Corporate Competence Center Embedded Linux
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