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Date: Tue, 1 Aug 2017 08:51:06 +0200
From: Cornelia Huck <cohuck@redhat.com>
To: David Hildenbrand <david@redhat.com>
Cc: Christoffer Dall <cdall@linaro.org>,
        "Longpeng(Mike)" <longpeng2@huawei.com>, pbonzini@redhat.com,
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        linux-kernel@vger.kernel.org, weidong.huang@huawei.com,
        arei.gonglei@huawei.com, wangxinxin.wang@huawei.com,
        longpeng.mike@gmail.com
Subject: Re: [RFC] KVM: optimize the kvm_vcpu_on_spin
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On Mon, 31 Jul 2017 19:32:26 +0200
David Hildenbrand <david@redhat.com> wrote:

> This one should work for s390x, no caching (or special access patterns
> like on x86) needed:
> 
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -2447,6 +2447,11 @@ int kvm_arch_vcpu_runnable(struct kvm_vcpu *vcpu)
>         return kvm_s390_vcpu_has_irq(vcpu, 0);
>  }
> 
> +bool kvm_arch_vcpu_in_kernel(struct kvm_vcpu *vcpu)
> +{
> +       return !(vcpu->arch.sie_block->gpsw.mask & PSW_MASK_PSTATE);
> +}
> +
>  void kvm_s390_vcpu_block(struct kvm_vcpu *vcpu)
>  {
>         atomic_or(PROG_BLOCK_SIE, &vcpu->arch.sie_block->prog20);

Yes, that should work.