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Date: Thu, 21 May 2015 21:30:16 +0200 (CEST)
From: Thomas Gleixner <tglx@linutronix.de>
To: Borislav Petkov <bp@suse.de>
cc: Huang Rui <ray.huang@amd.com>,
        One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk>,
        Ingo Molnar <mingo@kernel.org>, Len Brown <lenb@kernel.org>,
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        =?ISO-8859-15?Q?Fr=E9d=E9ric_Weisbecker?= <fweisbec@gmail.com>,
        Andy Lutomirski <luto@amacapital.net>
Subject: Re: [RFC PATCH 2/4] x86, mwaitt: introduce mwaitx idle with a
 configurable timer
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On Thu, 21 May 2015, Borislav Petkov wrote:

> On Thu, May 21, 2015 at 10:56:32PM +0800, Huang Rui wrote:
> > Looks like good use case. Boris, could we try to implement it?
> 
> Andy had some suggestions on how to do it here:
> 
> https://lkml.kernel.org/r/555D3629.8080002@kernel.org
> 
> which should be doable. Also, you'd probably need to set ECX[0]=0b too,
> so that MWAITX doesn't get woken up by interrupts while MWAIT-ing with
> interrupts disabled. I.e., this sequence:
> 
> cli
> rdtsc
> shove the computed timeout into ebx
> mov $2,%ecx				# this enables the timer and disables IRQs while MWAITing
> mwaitx
> sti

And the above sucks for udelay, because you disable interrupts for
random amounts of time.

Thanks,

	tglx