From mboxrd@z Thu Jan  1 00:00:00 1970
From: Davidlohr Bueso <dave@stgolabs.net>
Subject: Re: [PATCH resend] x86,kvm: Add a kernel parameter to disable PV
 spinlock
Date: Mon, 4 Sep 2017 15:21:57 -0700
Message-ID: <20170904222157.GD17982@linux-80c1.suse>
References: <20170904142836.15446-1-osalvador@suse.de>
 <20170904144011.gp7hpis6usjehbuf@hirez.programming.kicks-ass.net>
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Cc: Oscar Salvador <osalvador@suse.de>, Ingo Molnar <mingo@kernel.org>,
        Paolo Bonzini <pbonzini@redhat.com>,
        "H . Peter Anvin" <hpa@zytor.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
        linux-doc@vger.kernel.org, Waiman Long <longman@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>
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On Mon, 04 Sep 2017, Peter Zijlstra wrote:

>For testing its trivial to hack your kernel and I don't feel this is
>something an Admin can make reasonable decisions about.
>
>So why? In general less knobs is better.

+1.

Also, note how b8fa70b51aa (xen, pvticketlocks: Add xen_nopvspin parameter
to disable xen pv ticketlocks) has no justification as to why its wanted
in the first place. The only thing I could find was from 15a3eac0784
(xen/spinlock: Document the xen_nopvspin parameter):

"Useful for diagnosing issues and comparing benchmarks in over-commit CPU scenarios."

So I vote for no additional knobs, specially for such core code.

Thanks,
Davidlohr