linux-kernel - Re: [PATCH v4 1/2] KVM: nVMX: enhance allocate/free

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Message-ID: <55F9323A.3080900@siemens.com>
Date:	Wed, 16 Sep 2015 11:11:22 +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 v4 1/2] KVM: nVMX: enhance allocate/free_vpid to handle
 shadow vpid

On 2015-09-16 09:19, 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 | 23 +++++++++++------------
>  1 file changed, 11 insertions(+), 12 deletions(-)
> 
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 9ff6a3f..c5222b8 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -4155,29 +4155,28 @@ 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;
>  
> -	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);
> -	}
> +	else
> +		vpid = 0;
>  	spin_unlock(&vmx_vpid_lock);
> +	return vpid;
>  }
>  
> -static void free_vpid(struct vcpu_vmx *vmx)
> +static void free_vpid(int vpid)
>  {
>  	if (!enable_vpid)

|| vpid == 0

Otherwise you clear bit zero and cause the next allocate_vpid return 0 -
from the bitmap.

Jan

>  		return;
>  	spin_lock(&vmx_vpid_lock);
> -	if (vmx->vpid != 0)
> -		__clear_bit(vmx->vpid, vmx_vpid_bitmap);
> +	__clear_bit(vpid, vmx_vpid_bitmap);
>  	spin_unlock(&vmx_vpid_lock);
>  }
>  
> @@ -8482,7 +8481,7 @@ 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 +8500,7 @@ 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 +8576,7 @@ 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);
>  }
> 

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