Received-SPF: softfail (google.com: domain of transitioning linux-kernel-owner@vger.kernel.org does not designate 23.128.96.19 as permitted sender) client-ip=23.128.96.19;
Date:   Wed, 30 Mar 2022 00:07:01 +0000
From:   Sean Christopherson <seanjc@google.com>
To:     Wanpeng Li <kernellwp@gmail.com>
Cc:     linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
        Paolo Bonzini <pbonzini@redhat.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Jim Mattson <jmattson@google.com>,
        Joerg Roedel <joro@8bytes.org>
Subject: Re: [PATCH RESEND 3/5] KVM: X86: Boost vCPU which is in critical
 section
Message-ID: <YkOfJeXm8MiMOEyh@google.com>
References: <1648216709-44755-1-git-send-email-wanpengli@tencent.com>
 <1648216709-44755-4-git-send-email-wanpengli@tencent.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <1648216709-44755-4-git-send-email-wanpengli@tencent.com>
Precedence: bulk

On Fri, Mar 25, 2022, Wanpeng Li wrote:
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 425fd7f38fa9..6b300496bbd0 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -10375,6 +10375,28 @@ static int vcpu_run(struct kvm_vcpu *vcpu)
>  	return r;
>  }
>  
> +static int kvm_vcpu_non_preemptable(struct kvm_vcpu *vcpu)

s/preemtable/preemptible

And I'd recommend inverting the return, and also return a bool, i.e.

static bool kvm_vcpu_is_preemptible(struct kvm_vcpu *vcpu)

> +{
> +	int count;
> +
> +	if (!vcpu->arch.pv_pc.preempt_count_enabled)
> +		return 0;
> +
> +	if (!kvm_read_guest_cached(vcpu->kvm, &vcpu->arch.pv_pc.preempt_count_cache,
> +	    &count, sizeof(int)))
> +		return (count & ~PREEMPT_NEED_RESCHED);

This cements PREEMPT_NEED_RESCHED into KVM's guest/host ABI.  I doubt the sched
folks will be happy with that.

> +
> +	return 0;
> +}
> +