Commit 71710cd3 authored Oct 18, 2016 by James Morse Committed by Greg Kroah-Hartman Dec 08, 2016

arm64: suspend: Reconfigure PSTATE after resume from idle



commit d08544127d9fb4505635e3cb6871fd50a42947bd upstream.

The suspend/resume path in kernel/sleep.S, as used by cpu-idle, does not
save/restore PSTATE. As a result of this cpufeatures that were detected
and have bits in PSTATE get lost when we resume from idle.

UAO gets set appropriately on the next context switch. PAN will be
re-enabled next time we return from user-space, but on a preemptible
kernel we may run work accessing user space before this point.

Add code to re-enable theses two features in __cpu_suspend_exit().
We re-use uao_thread_switch() passing current.

Signed-off-by: James Morse <james.morse@arm.com>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
[Removed UAO hooks and commit-message references: this feature is not
 present in v4.4]
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent d24207a0

arch/arm64/kernel/suspend.c

+9 −0

Original line number	Diff line number	Diff line
		#include <linux/ftrace.h>
		#include <linux/percpu.h>
		#include <linux/slab.h>
		#include <asm/alternative.h>
		#include <asm/cacheflush.h>
		#include <asm/cpufeature.h>
		#include <asm/debug-monitors.h>
		#include <asm/pgtable.h>
		#include <asm/memory.h>
		@@ -110,6 +112,13 @@ int cpu_suspend(unsigned long arg, int (*fn)(unsigned long))
		*/
		set_my_cpu_offset(per_cpu_offset(smp_processor_id()));

		/*
		* PSTATE was not saved over suspend/resume, re-enable any
		* detected features that might not have been set correctly.
		*/
		asm(ALTERNATIVE("nop", SET_PSTATE_PAN(1), ARM64_HAS_PAN,
		CONFIG_ARM64_PAN));

		/*
		* Restore HW breakpoint registers to sane values
		* before debug exceptions are possibly reenabled