linux-kernel - Re: [PATCH 1/1] locking/qspinlock/x86: Avoid test-and-set when PV

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Message-ID: <20171024081345.GK3165@worktop.lehotels.local>
Date:   Tue, 24 Oct 2017 10:13:45 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Eduardo Valentin <eduval@...zon.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>, rkrcmar@...hat.com,
        Jonathan Corbet <corbet@....net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        Waiman Long <longman@...hat.com>, kvm@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        "Jan H . Schoenherr" <jschoenh@...zon.de>,
        Anthony Liguori <aliguori@...zon.com>
Subject: Re: [PATCH 1/1] locking/qspinlock/x86: Avoid test-and-set when
 PV_DEDICATED is set

On Mon, Oct 23, 2017 at 05:44:27PM -0700, Eduardo Valentin wrote:
> @@ -46,6 +48,8 @@ static inline bool virt_spin_lock(struct qspinlock *lock)
>  	if (!static_cpu_has(X86_FEATURE_HYPERVISOR))
>  		return false;
>  
> +	if (kvm_para_has_feature(KVM_FEATURE_PV_DEDICATED))
> +		return false;
>  	/*
>  	 * On hypervisors without PARAVIRT_SPINLOCKS support we fall
>  	 * back to a Test-and-Set spinlock, because fair locks have

This does not apply. Much has been changed here recently.