On 16.07.2019 12:39, Roger Pau Monné  wrote:
> On Wed, Jul 03, 2019 at 12:59:36PM +0000, Jan Beulich wrote:
>> While the MWAIT idle driver already takes it to mean an actual C state,
>> the ACPI idle driver so far used it as a list index. The list index,
>> however, is an implementation detail of Xen and affected by firmware
>> settings (i.e. not necessarily uniform for a particular system).
>>
>> While touching this code also avoid invoking menu_get_trace_data()
>> when tracing is not active. For consistency do this also for the
>> MWAIT driver.
>>
>> Note that I'm intentionally not adding any sorting logic to set_cx():
>> Before and after this patch we assume entries to arrive in order, so
>> this would be an orthogonal change.
>>
>> Take the opportunity and add minimal documentation for the command line
>> option.
>>
>> Signed-off-by: Jan Beulich <[email protected]>
> 
> Just one comment, regardless of which:
> 
> Reviewed-by: Roger Pau Monné <[email protected]>

Thanks.

>> --- a/xen/arch/x86/acpi/cpu_idle.c
>> +++ b/xen/arch/x86/acpi/cpu_idle.c
>> @@ -103,7 +103,7 @@ bool lapic_timer_init(void)
>>    }
>>    
>>    void (*__read_mostly pm_idle_save)(void);
>> -unsigned int max_cstate __read_mostly = ACPI_PROCESSOR_MAX_POWER - 1;
>> +unsigned int max_cstate __read_mostly = UINT_MAX;
> 
> Not sure whether it would be clearer to just use
> XEN_SYSCTL_CX_UNLIMITED here instead of UINT_MAX.

Well, the patch adds a BUILD_BUG_ON() to verify both match. If
they didn't, translation would be required. The variable and its
use strictly want it to be UINT_MAX.

Jan
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