On Wed, 29 Mar 2017, Dou Liyang wrote:
> The purpose of this patchset is Unifing these setup steps and executing as
> soon as possible as follows:
>
> start_kernel
> ---------------+
> |
> |
> |
> | init_IRQ
> +---->---+----+
> | |
> | | +--------------------+
> | +----> | 4. init_bsp_APIC |
> | +--------------------+
> v
>
> By the way, Also fix a bug about kexec[3].
>
>
> Some doubts, need help:
>
> 1. Patchset has influence on IOMMU in enable_IR_x2apic(). Not sure
> it can be in advance?
That should work.
> 2. Due to
>
> Commit 8c3ba8d04924 ("x86, apic: ack all pending irqs when crashed/on kexec")
>
> ..., patchset also needs TSC and uses the "cpu_khz" in setup_local_APIC().
> And a warning[4] will be triggered when crashed/on kexec. Not sure how to
> modify?
The local APIC timer initialization cannot be run from init_IRQ().
The problem here is that CPU and TSC frequency calibration depends on the
PIT/HPET interrupt (irq 0) working for machines which cannot calibrate via
MSR/CPUID or if fast calibration via PIT fails.
So we need to split that initialization into several parts:
1) Set up the APIC/IOAPIC (including testing whether the timer interrupt
works)
2) Calibrate TSC
3) Set up the local APIC timer
Thanks,
tglx
