On Thu, Jan 26, 2012 at 07:47:17PM +0400, Michael Tokarev wrote:

26.01.2012 18:45, Kirill A. Shutemov wrote:

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From: Thomas Renninger<redacted>

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.

[]

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 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.

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  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.

-- 
 Kirill A. Shutemov