linux-kernel - Re: [PATCH 2/6] KVM: x86: decouple irqchip_in_kernel() and pic

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Date:   Thu, 24 Nov 2016 11:55:51 -0500 (EST)
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Radim Krčmář <rkrcmar@...hat.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH 2/6] KVM: x86: decouple irqchip_in_kernel() and
 pic_irqchip()


> irqchip_in_kernel() tried to save a bit by reusing pic_irqchip(), but it
> just complicated the code.
> Add kvm->arch.irqchip_kvm that matches kvm->arch.irqchip_split.
> (Turning them into an exclusive type would be nicer.)

Then do it. ;)

Paolo

> Signed-off-by: Radim Krčmář <rkrcmar@...hat.com>
> ---
>  arch/x86/include/asm/kvm_host.h |  1 +
>  arch/x86/kvm/irq.h              | 13 +++++++------
>  arch/x86/kvm/x86.c              |  3 ++-
>  3 files changed, 10 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/x86/include/asm/kvm_host.h
> b/arch/x86/include/asm/kvm_host.h
> index bdde80731f49..929228ec2839 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -778,6 +778,7 @@ struct kvm_arch {
>  
>  	u64 disabled_quirks;
>  
> +	bool irqchip_kvm;
>  	bool irqchip_split;
>  	u8 nr_reserved_ioapic_pins;
>  
> diff --git a/arch/x86/kvm/irq.h b/arch/x86/kvm/irq.h
> index 035731eb3897..8536be85d529 100644
> --- a/arch/x86/kvm/irq.h
> +++ b/arch/x86/kvm/irq.h
> @@ -96,15 +96,16 @@ static inline int irqchip_split(struct kvm *kvm)
>  	return kvm->arch.irqchip_split;
>  }
>  
> +static inline int irqchip_kvm(struct kvm *kvm)
> +{
> +	return kvm->arch.irqchip_kvm;
> +}
> +
>  static inline int irqchip_in_kernel(struct kvm *kvm)
>  {
> -	struct kvm_pic *vpic = pic_irqchip(kvm);
> -	bool ret;
> +	bool ret = irqchip_kvm(kvm) || irqchip_split(kvm);
>  
> -	ret = (vpic != NULL);
> -	ret |= irqchip_split(kvm);
> -
> -	/* Read vpic before kvm->irq_routing.  */
> +	/* Matches with wmb after initializing kvm->irq_routing. */
>  	smp_rmb();
>  	return ret;
>  }
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index dbed51045c37..dd8431a7e18b 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -3928,8 +3928,9 @@ long kvm_arch_vm_ioctl(struct file *filp,
>  			mutex_unlock(&kvm->slots_lock);
>  			goto create_irqchip_unlock;
>  		}
> -		/* Write kvm->irq_routing before kvm->arch.vpic.  */
> +		/* Write kvm->irq_routing before enabling irqchip_in_kernel. */
>  		smp_wmb();
> +		kvm->arch.irqchip_kvm = true;
>  		kvm->arch.vpic = vpic;
>  	create_irqchip_unlock:
>  		mutex_unlock(&kvm->lock);
> --
> 2.10.2
> 
>