linux-kernel - Re: [PATCH 1/3] KVM: x86: check_nested

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Date:   Mon, 20 Apr 2020 10:47:16 +0200
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <sean.j.christopherson@...el.com>,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH 1/3] KVM: x86: check_nested_events is never NULL

Paolo Bonzini <pbonzini@...hat.com> writes:

> Both Intel and AMD now implement it, so there is no need to check if the
> callback is implemented.
>
> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
> ---
>  arch/x86/kvm/x86.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 59958ce2b681..0492baeb78ab 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -7699,7 +7699,7 @@ static int inject_pending_event(struct kvm_vcpu *vcpu)
>  	 * from L2 to L1 due to pending L1 events which require exit
>  	 * from L2 to L1.
>  	 */
> -	if (is_guest_mode(vcpu) && kvm_x86_ops.check_nested_events) {
> +	if (is_guest_mode(vcpu)) {
>  		r = kvm_x86_ops.check_nested_events(vcpu);
>  		if (r != 0)
>  			return r;
> @@ -7761,7 +7761,7 @@ static int inject_pending_event(struct kvm_vcpu *vcpu)
>  		 * proposal and current concerns.  Perhaps we should be setting
>  		 * KVM_REQ_EVENT only on certain events and not unconditionally?
>  		 */
> -		if (is_guest_mode(vcpu) && kvm_x86_ops.check_nested_events) {
> +		if (is_guest_mode(vcpu)) {
>  			r = kvm_x86_ops.check_nested_events(vcpu);
>  			if (r != 0)
>  				return r;
> @@ -8527,7 +8527,7 @@ static inline int vcpu_block(struct kvm *kvm, struct kvm_vcpu *vcpu)
>  
>  static inline bool kvm_vcpu_running(struct kvm_vcpu *vcpu)
>  {
> -	if (is_guest_mode(vcpu) && kvm_x86_ops.check_nested_events)
> +	if (is_guest_mode(vcpu))
>  		kvm_x86_ops.check_nested_events(vcpu);
>  
>  	return (vcpu->arch.mp_state == KVM_MP_STATE_RUNNABLE &&

While the callback is implemented for both VMX and SVM, it can still be
NULL when !nested (thus patch subject is a bit misleading) but
is_guest_mode() implies this is not the case.

Reviewed-by: Vitaly Kuznetsov <vkuznets@...hat.com>

-- 
Vitaly