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From: Peter Zijlstra <peterz@infradead.org>
To: Oscar Salvador <osalvador@suse.de>
Cc: 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>
Subject: Re: [PATCH resend] x86,kvm: Add a kernel parameter to disable PV spinlock
Date: Mon, 4 Sep 2017 16:40:12 +0200	[thread overview]
Message-ID: <20170904144011.gp7hpis6usjehbuf@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20170904142836.15446-1-osalvador@suse.de>

On Mon, Sep 04, 2017 at 04:28:36PM +0200, Oscar Salvador wrote:
> This is just a resend of Waiman Long's patch.
> I could not find why it was not merged to upstream, so I thought
> to give it another chance.
> What follows is what Waiman Long wrote.
> 
> Xen has an kernel command line argument "xen_nopvspin" to disable
> paravirtual spinlocks. This patch adds a similar "kvm_nopvspin"
> argument to disable paravirtual spinlocks for KVM. This can be useful
> for testing as well as allowing administrators to choose unfair lock
> for their KVM guests if they want to.

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.

  reply	other threads:[~2017-09-04 14:40 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-09-04 14:28 [PATCH resend] x86,kvm: Add a kernel parameter to disable PV spinlock Oscar Salvador
2017-09-04 14:40 ` Peter Zijlstra [this message]
2017-09-04 19:32   ` Waiman Long
2017-09-04 22:21   ` Davidlohr Bueso
2017-09-05  6:28     ` Juergen Gross
2017-09-05  6:57       ` Oscar Salvador
2017-09-05  8:07         ` Peter Zijlstra
2017-09-05  6:58       ` Peter Zijlstra
2017-09-05  7:35         ` Juergen Gross
2017-09-05  8:10           ` Peter Zijlstra
2017-09-05  8:14             ` Juergen Gross
2017-09-05  8:28               ` Peter Zijlstra
2017-09-05  8:52                 ` Juergen Gross
2017-09-05  9:03                   ` Peter Zijlstra
2017-09-05  9:11                     ` Juergen Gross

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