diff options
| author | David Woodhouse <dwmw@amazon.co.uk> | 2024-08-02 15:55:54 +0200 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2024-08-02 18:27:05 +0200 |
| commit | 70e6b7d9ae3c63df90a7bba7700e8d5c300c3c60 (patch) | |
| tree | 419b1082f71a6467629865776227b3ab9d07ae48 /arch/x86/kernel | |
| parent | x86/tsc: Use topology_max_packages() to get package number (diff) | |
| download | linux-70e6b7d9ae3c63df90a7bba7700e8d5c300c3c60.tar.xz linux-70e6b7d9ae3c63df90a7bba7700e8d5c300c3c60.zip | |
x86/i8253: Disable PIT timer 0 when not in use
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
Diffstat (limited to 'arch/x86/kernel')
| -rw-r--r-- | arch/x86/kernel/i8253.c | 11 |
1 files changed, 9 insertions, 2 deletions
diff --git a/arch/x86/kernel/i8253.c b/arch/x86/kernel/i8253.c index 2b7999a1a50a..80e262bb627f 100644 --- a/arch/x86/kernel/i8253.c +++ b/arch/x86/kernel/i8253.c @@ -8,6 +8,7 @@ #include <linux/timex.h> #include <linux/i8253.h> +#include <asm/hypervisor.h> #include <asm/apic.h> #include <asm/hpet.h> #include <asm/time.h> @@ -39,9 +40,15 @@ static bool __init use_pit(void) bool __init pit_timer_init(void) { - if (!use_pit()) + if (!use_pit()) { + /* + * Don't just ignore the PIT. Ensure it's stopped, because + * VMMs otherwise steal CPU time just to pointlessly waggle + * the (masked) IRQ. + */ + clockevent_i8253_disable(); return false; - + } clockevent_i8253_init(true); global_clock_event = &i8253_clockevent; return true; |