x86/i8253: Disable PIT timer 0 when not in use

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commit 70e6b7d9ae upstream.

Leaving the PIT interrupt running can cause noticeable steal time for
virtual guests. The VMM generally has a timer which toggles the IRQ input
to the PIC and I/O APIC, which takes CPU time away from the guest. Even
on real hardware, running the counter may use power needlessly (albeit
not much).

Make sure it's turned off if it isn't going to be used.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Michael Kelley <mhkelley@outlook.com>
Link: https://lore.kernel.org/all/20240802135555.564941-1-dwmw2@infradead.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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David Woodhouse 2024-08-02 14:55:54 +01:00 • committed by Greg Kroah-Hartman

parent 3aa5254d80

commit caae544264

3 changed files with 19 additions and 6 deletions

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11

arch/x86/kernel/i8253.c

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13

drivers/clocksource/i8253.c

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1

include/linux/i8253.h

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