linux-kernel - Re: [PATCH v2 08/13] KVM: x86: Dynamically allocate per-vCPU emulation context

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Date:   Tue, 3 Mar 2020 08:52:04 -0800
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Vitaly Kuznetsov <vkuznets@...hat.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 08/13] KVM: x86: Dynamically allocate per-vCPU
 emulation context

On Wed, Feb 26, 2020 at 06:29:56PM +0100, Vitaly Kuznetsov wrote:
> Sean Christopherson <sean.j.christopherson@...el.com> writes:
> > @@ -9409,6 +9451,9 @@ void kvm_arch_vcpu_destroy(struct kvm_vcpu *vcpu)
> >  
> >  	kvm_x86_ops->vcpu_free(vcpu);
> >  
> > +	if (vcpu->arch.emulate_ctxt)
> > +		kmem_cache_free(x86_emulator_cache, vcpu->arch.emulate_ctxt);
> 
> Checking for NULL here seems superfluous as we create the context in
> kvm_arch_vcpu_create() unconditionally. I'd suggest we move the check to 
> "[PATCH v2 12/13] KVM: x86: Add variable to control existence of
> emulator" where 'enable_emulator' global is added.

Ya, checking here is premature.

> > +
> >  	free_cpumask_var(vcpu->arch.wbinvd_dirty_mask);
> >  	kmem_cache_free(x86_fpu_cache, vcpu->arch.user_fpu);
> >  	kmem_cache_free(x86_fpu_cache, vcpu->arch.guest_fpu);
> 
> -- 
> Vitaly
>