linux-kernel - Re: [67/90] intel idle: Make idle driver more robust

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Date:	Thu, 26 Jan 2012 18:07:45 +0200
From:	"Kirill A. Shutemov" <kirill@...temov.name>
To:	Greg KH <gregkh@...e.de>
Cc:	Michael Tokarev <mjt@....msk.ru>, linux-kernel@...r.kernel.org,
	stable@...r.kernel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Thomas Renninger <trenn@...e.de>,
	Bruno Friedmann <bruno@...a-net.ch>,
	Len Brown <len.brown@...el.com>
Subject: Re: [67/90] intel idle: Make idle driver more robust

On Thu, Jan 26, 2012 at 07:59:25AM -0800, Greg KH wrote:
> On Thu, Jan 26, 2012 at 05:54:27PM +0200, Kirill A. Shutemov wrote:
> > On Thu, Jan 26, 2012 at 07:47:17PM +0400, Michael Tokarev wrote:
> > > 26.01.2012 18:45, Kirill A. Shutemov wrote:
> > > 
> > > >>From: Thomas Renninger<trenn@...e.de>
> > > >>
> > > >>commit 5c2a9f06a9cd7194f884cdc88144866235dec07d upstream.
> > > >>
> > > >>kvm -cpu host passes the original cpuid info to the guest.
> > > >>
> > > >>Latest kvm version seem to return true for mwait_leaf cpuid
> > > >>function on recent Intel CPUs. But it does not return mwait
> > > >>C-states (mwait_substates), instead zero is returned.
> > > >>
> > > []
> > > >>  drivers/idle/intel_idle.c |    3 ++-
> > > >>  1 file changed, 2 insertions(+), 1 deletion(-)
> > > >>
> > > >>--- a/drivers/idle/intel_idle.c
> > > >>+++ b/drivers/idle/intel_idle.c
> > > >>@@ -321,7 +321,8 @@ static int intel_idle_probe(void)
> > > >>  	cpuid(CPUID_MWAIT_LEAF,&eax,&ebx,&ecx,&mwait_substates);
> > > >>
> > > >>  	if (!(ecx&  CPUID5_ECX_EXTENSIONS_SUPPORTED) ||
> > > >>-		!(ecx&  CPUID5_ECX_INTERRUPT_BREAK))
> > > >>+	    !(ecx&  CPUID5_ECX_INTERRUPT_BREAK) ||
> > > >>+	    !mwait_substates)
> > > >>  			return -ENODEV;
> > > >
> > > >It breaks build for me.
> > > []
> > > >   CC      drivers/idle/intel_idle.o
> > > >/home/space/kas/git/public/linux-3.0-mid/drivers/idle/intel_idle.c: In function ‘intel_idle_probe’:
> > > >/home/space/kas/git/public/linux-3.0-mid/drivers/idle/intel_idle.c:508:7: error: ‘mwait_substates’ undeclared (first use in this function)
> > > >/home/space/kas/git/public/linux-3.0-mid/drivers/idle/intel_idle.c:508:7: note: each undeclared identifier is reported only once for each function it appears in
> > > >make[3]: *** [drivers/idle/intel_idle.o] Error 1
> > > >
> > > >Variable 'substates' hasn't renamed to 'mwait_substates' in 3.0.
> > > >See c423628 intel_idle: delete substates DEBUG modparam
> > > 
> > > I wonder why in my 3.0.18 this variable is properly defined
> > > in the same file, in line 77:
> > > 
> > > ...
> > > 74 /* intel_idle.max_cstate=0 disables driver */
> > > 75 static int max_cstate = MWAIT_MAX_NUM_CSTATES - 1;
> > > 76
> > > 77 static unsigned int mwait_substates;
> > > 78
> > > 79 #define LAPIC_TIMER_ALWAYS_RELIABLE 0xFFFFFFFF
> > > ...
> > 
> > Oosp. Sorry for noise. My local patch breaks it.
> 
> So, 3.0.18 is just fine, right?

Yes.

-- 
 Kirill A. Shutemov
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