linux-kernel - Re: [PATCH v3 4/4] KVM: Add flush_on

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Message-ID: <20171110100838.eqfccs735x4ghw6q@hirez.programming.kicks-ass.net>
Date:   Fri, 10 Nov 2017 11:08:38 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Wanpeng Li <kernellwp@...il.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Kr??m???? <rkrcmar@...hat.com>,
        Wanpeng Li <wanpeng.li@...mail.com>
Subject: Re: [PATCH v3 4/4] KVM: Add flush_on_enter before guest enter

On Fri, Nov 10, 2017 at 01:49:47AM -0800, Wanpeng Li wrote:
> @@ -2887,7 +2899,7 @@ static void kvm_steal_time_set_preempted(struct kvm_vcpu *vcpu)
>  	if (!(vcpu->arch.st.msr_val & KVM_MSR_ENABLED))
>  		return;
>  
> -	vcpu->arch.st.steal.preempted = KVM_VCPU_PREEMPTED;
> +	vcpu->arch.st.steal.preempted |= KVM_VCPU_PREEMPTED;

I don't understand this one... If there is concurrency its wrong, if
there is no concurrency it still doesn't make sense as there should not
be any FLUSH flags to preserve..

>  
>  	kvm_write_guest_offset_cached(vcpu->kvm, &vcpu->arch.st.stime,
>  			&vcpu->arch.st.steal.preempted,