linux-kernel - Re: [PATCH v3] KVM: vgic: Use wrapper function to lock/unlock all vcpus in kvm_vgic

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Date:   Fri, 06 Dec 2019 11:46:41 +0000
From:   Marc Zyngier <maz@...nel.org>
To:     linmiaohe <linmiaohe@...wei.com>
Cc:     <pbonzini@...hat.com>, <rkrcmar@...hat.com>, <james.morse@....com>,
        <julien.thierry.kdev@...il.com>, <suzuki.poulose@....com>,
        <christoffer.dall@....com>, <catalin.marinas@....com>,
        <eric.auger@...hat.com>, <gregkh@...uxfoundation.org>,
        <will@...nel.org>, <andre.przywara@....com>, <tglx@...utronix.de>,
        <steven.price@....com>, <linux-arm-kernel@...ts.infradead.org>,
        <kvmarm@...ts.cs.columbia.edu>, <linux-kernel@...r.kernel.org>,
        <kvm@...r.kernel.org>
Subject: Re: [PATCH v3] KVM: vgic: Use wrapper function to lock/unlock all  vcpus in kvm_vgic_create()

On 2019-11-30 02:45, linmiaohe wrote:
> From: Miaohe Lin <linmiaohe@...wei.com>
>
> Use wrapper function lock_all_vcpus()/unlock_all_vcpus()
> in kvm_vgic_create() to remove duplicated code dealing
> with locking and unlocking all vcpus in a vm.
>
> Reviewed-by: Eric Auger <eric.auger@...hat.com>
> Reviewed-by: Steven Price <steven.price@....com>
> Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
> ---
> -v2:
> 	Fix some spelling mistake in patch title and commit log.
> -v3:
> 	Remove the comment that no longer makes sense.
> ---
>  virt/kvm/arm/vgic/vgic-init.c | 19 ++++---------------
>  1 file changed, 4 insertions(+), 15 deletions(-)
>
> diff --git a/virt/kvm/arm/vgic/vgic-init.c 
> b/virt/kvm/arm/vgic/vgic-init.c
> index b3c5de48064c..22ff73ecac80 100644
> --- a/virt/kvm/arm/vgic/vgic-init.c
> +++ b/virt/kvm/arm/vgic/vgic-init.c
> @@ -70,7 +70,7 @@ void kvm_vgic_early_init(struct kvm *kvm)
>   */
>  int kvm_vgic_create(struct kvm *kvm, u32 type)
>  {
> -	int i, vcpu_lock_idx = -1, ret;
> +	int i, ret;
>  	struct kvm_vcpu *vcpu;
>
>  	if (irqchip_in_kernel(kvm))
> @@ -86,17 +86,9 @@ int kvm_vgic_create(struct kvm *kvm, u32 type)
>  		!kvm_vgic_global_state.can_emulate_gicv2)
>  		return -ENODEV;
>
> -	/*
> -	 * Any time a vcpu is run, vcpu_load is called which tries to grab 
> the
> -	 * vcpu->mutex.  By grabbing the vcpu->mutex of all VCPUs we ensure
> -	 * that no other VCPUs are run while we create the vgic.
> -	 */
>  	ret = -EBUSY;
> -	kvm_for_each_vcpu(i, vcpu, kvm) {
> -		if (!mutex_trylock(&vcpu->mutex))
> -			goto out_unlock;
> -		vcpu_lock_idx = i;
> -	}
> +	if (!lock_all_vcpus(kvm))
> +		return ret;
>
>  	kvm_for_each_vcpu(i, vcpu, kvm) {
>  		if (vcpu->arch.has_run_once)
> @@ -125,10 +117,7 @@ int kvm_vgic_create(struct kvm *kvm, u32 type)
>  		INIT_LIST_HEAD(&kvm->arch.vgic.rd_regions);
>
>  out_unlock:
> -	for (; vcpu_lock_idx >= 0; vcpu_lock_idx--) {
> -		vcpu = kvm_get_vcpu(kvm, vcpu_lock_idx);
> -		mutex_unlock(&vcpu->mutex);
> -	}
> +	unlock_all_vcpus(kvm);
>  	return ret;
>  }

Applied, thanks.

         M.
-- 
Jazz is not dead. It just smells funny...