linux-kernel - RE: [PATCH V2 0/2] measure SMI cost (user)

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Message-ID: <37D7C6CF3E00A74B8858931C1DB2F077537053C9@SHSMSX103.ccr.corp.intel.com>
Date:   Fri, 2 Jun 2017 15:45:11 +0000
From:   "Liang, Kan" <kan.liang@...el.com>
To:     'Jiri Olsa' <jolsa@...hat.com>,
        'Peter Zijlstra' <peterz@...radead.org>
CC:     "'acme@...nel.org'" <acme@...nel.org>,
        "'tglx@...utronix.de'" <tglx@...utronix.de>,
        "'mingo@...hat.com'" <mingo@...hat.com>,
        "'linux-kernel@...r.kernel.org'" <linux-kernel@...r.kernel.org>,
        "'eranian@...gle.com'" <eranian@...gle.com>,
        "'jolsa@...nel.org'" <jolsa@...nel.org>,
        "'elliott@....com'" <elliott@....com>,
        "'ak@...ux.intel.com'" <ak@...ux.intel.com>
Subject: RE: [PATCH V2 0/2] measure SMI cost (user)



> >
> > On Mon, May 29, 2017 at 02:52:39PM +0200, Peter Zijlstra wrote:
> > > On Mon, May 29, 2017 at 02:46:37PM +0200, Jiri Olsa wrote:
> > >
> > > > for some reason I can't get single SMI count generated, is there a
> > > > setup/bench that would provoke that?
> > >
> > > Not having SMIs is a good thing ;-)
> > >
> > > Not sure we can tickle them in a reliable way.
> >
> > yea I saw some counts last time, now just zero so I was wondering if
> > it's working
> >
> 
> We have internal test case which can generate SMI, but I cannot publish the
> test case. Sorry about that.
> 

APM_CNT (0xB2) could be used to trigger SMI#.

It's documented in PCH datasheet.
https://www.intel.com/content/dam/www/public/us/en/
documents/datasheets/9-series-chipset-pch-datasheet.pdf

APM_CNT-Advanced Power Management Control Port Register 
I/O Address: B2h 
Attribute: R/W 
Default Value: 00h 
Size: 8 bits
Lockable: No 
Usage: Legacy Only
Power Well: Core
Bit Description
7:0 Used to pass an APM command between the OS and the SMI handler. 
Writes to this port not only store data in the APMC register, 
but also generates an SMI# when the APMC_EN bit is set.

You can write a byte to port 0xB2 to trigger an SMI#

Thanks,
Kan