Messages in this thread | | | Date | Tue, 18 Jun 2019 07:43:48 +0200 (CEST) | From | Thomas Gleixner <> | Subject | Re: [PATCH v4 2/5] x86/umwait: Initialize umwait control values |
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On Mon, 17 Jun 2019, Fenghua Yu wrote: > On Tue, Jun 11, 2019 at 10:46:55PM +0200, Thomas Gleixner wrote: > > On Sun, 9 Jun 2019, Fenghua Yu wrote: > > > > Sounds good, but: > > > > > > > > > +#define MSR_IA32_UMWAIT_CONTROL_C02 BIT(0) > > > > > > > > > +static u32 umwait_control_cached = 100000; > > > > > > > > The code seems to disagree. > > > > > > The definition of bit[0] is: C0.2 is disabled when bit[0]=1. So > > > 100000 means C0.2 is enabled (and max time is 100000). > > > > which is totally non obvious. If you have to encode the control bit, then > > please make it explicit, i.e. mask out the disable bit in the initializer. > > Is this right? > > static u32 umwait_control_cached = 100000 & ~MSR_IA32_UMWAIT_CONTROL_C02_DISABLED;
Works, but looks pretty odd. I'd rather create an explicit initializer macro, something like:
UMWAIT_CTRL_VAL(100000, UMWAIT_DISABLED);
Hmm?
Thanks,
tglx
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