linux-kernel - Re: [PATCH v2 1/4] x86, mwaitt: add monitorx and mwaitx instruction

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Message-ID: <20150609082306.GN3644@twins.programming.kicks-ass.net>
Date:	Tue, 9 Jun 2015 10:23:06 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Huang Rui <ray.huang@....com>
Cc:	Borislav Petkov <bp@...e.de>,
	Andy Lutomirski <luto@...capital.net>,
	Thomas Gleixner <tglx@...utronix.de>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Len Brown <lenb@...nel.org>,
	John Stultz <john.stultz@...aro.org>,
	Frédéric Weisbecker <fweisbec@...il.com>,
	linux-kernel@...r.kernel.org, x86@...nel.org,
	Fengguang Wu <fengguang.wu@...el.com>,
	Aaron Lu <aaron.lu@...el.com>,
	Suravee Suthikulanit <suravee.suthikulpanit@....com>,
	Tony Li <tony.li@....com>, Ken Xue <ken.xue@....com>
Subject: Re: [PATCH v2 1/4] x86, mwaitt: add monitorx and mwaitx instruction

On Tue, Jun 09, 2015 at 11:13:38AM +0800, Huang Rui wrote:
> 
> MWAITX ECX[1]: enable timer if set
> MWAITX EBX[31:0]: max wait time expressed in SW P0 clocks
> 
> The software P0 frequency is the same as the TSC frequency.
> 
> Max timeout = EBX/(TSC frequency)

^ that, would make a lovely comment for this v

> +static inline void __mwaitx(unsigned long eax, unsigned long ebx,
> +			    unsigned long ecx)
> +{
> +	/* "mwaitx %eax, %ebx, %ecx;" */
> +	asm volatile(".byte 0x0f, 0x01, 0xfb;"
> +		     :: "a" (eax), "b" (ebx), "c" (ecx));
> +}
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