On Thu, 2023-02-09 at 20:32 +0000, Usama Arif wrote: > > I will let David confirm if this is correct and why he did it, but this > is what I thought while reviewing before posting v4: > > - At initial boot (system_state < SYSTEM_RUNNING), when mtrr_save_state > is called in do_cpu_up at roughly the same time so MTRR is going to be > the same, we can just save it once and then reuse for other secondary > cores as it wouldn't have changed for the rest of the do_cpu_up calls. > > - When the system is running and you offline and then online a CPU, you > want to make sure that hotplugged CPU gets the current MTRR (which might > have changed since boot?), incase the MTRR has changed after the system > has been booted, you save the MTRR of the first online CPU. When the > hotplugged CPU runs its initialisation code, its fixed-range MTRRs will > be updated with the newly saved fixed-range MTRRs. > > So mainly for hotplug, but will let David confirm. Sounds about right.
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