Patch "arm64: suspend: Reconfigure PSTATE after resume from idle" has been added to the 4.4-stable tree

Patch "arm64: suspend: Reconfigure PSTATE after resume from idle" has been added to the 4.4-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    arm64: suspend: Reconfigure PSTATE after resume from idle

to the 4.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     arm64-suspend-reconfigure-pstate-after-resume-from-idle.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From d08544127d9fb4505635e3cb6871fd50a42947bd Mon Sep 17 00:00:00 2001
From: James Morse <james.morse@arm.com>
Date: Tue, 18 Oct 2016 11:27:48 +0100
Subject: arm64: suspend: Reconfigure PSTATE after resume from idle

From: James Morse <james.morse@arm.com>

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>

---
 arch/arm64/kernel/suspend.c |    9 +++++++++
 1 file changed, 9 insertions(+)

--- a/arch/arm64/kernel/suspend.c
+++ b/arch/arm64/kernel/suspend.c
@@ -1,7 +1,9 @@
 #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>
@@ -111,6 +113,13 @@ int cpu_suspend(unsigned long arg, int (
 		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
 		 * through local_dbg_restore.


Patches currently in stable-queue which might be from james.morse@arm.com are

queue-4.4/arm64-mm-set-pstate.pan-from-the-cpu_enable_pan-call.patch
queue-4.4/arm64-suspend-reconfigure-pstate-after-resume-from-idle.patch
queue-4.4/arm64-cpufeature-schedule-enable-calls-instead-of-calling-them-via-ipi.patch