Commit 5bef0a15 authored Feb 13, 2020 by Johannes Berg Committed by Richard Weinberger Mar 29, 2020

um: Implement cpu_relax() as ndelay(1) for time-travel



In time-travel mode, cpu_relax() currently does actual CPU relax,
but that doesn't affect the simulation. Ideally, we wouldn't run
anything that uses it in simulation, but if we actually have virtio
devices combined with the same simulation it's possible. Implement
cpu_relax() as ndelay(1) in this case, using time_travel_ndelay(1)
directly to catch errors if this is used erroneously in builds that
don't set CONFIG_UML_TIME_TRAVEL_SUPPORT.

While at it, convert it to an __always_inline and also add that to
rep_nop() like the original does now.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Richard Weinberger <richard@nod.at>

parent 0bc8fb4d

arch/x86/um/asm/processor.h

+10 −2

Original line number	Diff line number	Diff line
		/* SPDX-License-Identifier: GPL-2.0 */
		#ifndef __UM_PROCESSOR_H
		#define __UM_PROCESSOR_H
		#include <linux/time-internal.h>

		/* include faultinfo structure */
		#include <sysdep/faultinfo.h>
		@@ -21,12 +22,19 @@
		#include <asm/user.h>

		/* REP NOP (PAUSE) is a good thing to insert into busy-wait loops. */
		static inline void rep_nop(void)
		static __always_inline void rep_nop(void)
		{
		__asm__ __volatile__("rep;nop": : :"memory");
		}

		#define cpu_relax() rep_nop()
		static __always_inline void cpu_relax(void)
		{
		if (time_travel_mode == TT_MODE_INFCPU \|\|
		time_travel_mode == TT_MODE_EXTERNAL)
		time_travel_ndelay(1);
		else
		rep_nop();
		}

		#define task_pt_regs(t) (&(t)->thread.regs)

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