Re: [PATCH v3 1/2] KVM: nVMX: enhance allocate/free_vpid to handle shadow vpid

[Wanpeng Li]

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@xxxxxxxxxxx>
> > ---
> >   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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