On Tue, 2025-03-11 at 15:59 +0100, Greg Kroah-Hartman wrote:
5.10-stable review patch. If anyone has any objections, please let me know.
From: David Woodhouse dwmw@amazon.co.uk
commit 70e6b7d9ae3c63df90a7bba7700e8d5c300c3c60 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
You probably want commit 531b2ca0a940ac ("clockevents/drivers/i8253: Fix stop sequence for timer 0") too, to make sure it *does* actually stop the PIT correctly.