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Re: [PATCH] x86/APIC: no need for timer calibration when using TDT

To: Jan Beulich <jbeulich@xxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
From: Andrew Cooper <amc96@xxxxxxxx>
Date: Thu, 20 Jan 2022 16:09:17 +0000
Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>
Delivery-date: Thu, 20 Jan 2022 16:09:25 +0000
List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

On 17/01/2022 10:32, Jan Beulich wrote:
> The only global effect of calibrate_APIC_clock() is the setting of
> "bus_scale"; the final __setup_APIC_LVTT(0) is (at best) redundant with
> the immediately following setup_APIC_timer() invocation. Yet "bus_scale"
> isn't used when using TDT. Avoid wasting 100ms for calibration in this
> case.
>
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

Acked-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

References:
- [PATCH] x86/APIC: no need for timer calibration when using TDT
  - From: Jan Beulich

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