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SubjectRe: [67/90] intel idle: Make idle driver more robust
26.01.2012 18:45, Kirill A. Shutemov wrote:

>> From: Thomas Renninger<trenn@suse.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
...

> Signed-off-by: Kirill A. Shutemov<kirill.shutemov@linux.intel.com>
> ---
> drivers/idle/intel_idle.c | 2 +-
> 1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c
> index 15d72ca..a1aecc3 100644
> --- a/drivers/idle/intel_idle.c
> +++ b/drivers/idle/intel_idle.c
> @@ -505,7 +505,7 @@ static int intel_idle_probe(void)
>
> if (!(ecx& CPUID5_ECX_EXTENSIONS_SUPPORTED) ||
> !(ecx& CPUID5_ECX_INTERRUPT_BREAK) ||
> - !mwait_substates)
> + !substates)

With this patch my build of 3.0.18 fails with "substates undeclared"
message...

>
> if (substates == 0) /* can over-ride via modparam */

And I don't have this context line in my version.

It is 3.0 from kernel.org patched by patch-3.0.18.xz

Thanks,

/mjt
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