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[PATCH 4.8 35/35] arm64: suspend: Reconfigure PSTATE after resume from idle

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4.8-stable review patch.  If anyone has any objections, please let me know.

------------------

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/arm64/include/asm/exec.h |    3 +++
 arch/arm64/kernel/process.c   |    3 ++-
 arch/arm64/kernel/suspend.c   |   11 +++++++++++
 3 files changed, 16 insertions(+), 1 deletion(-)

--- a/arch/arm64/include/asm/exec.h
+++ b/arch/arm64/include/asm/exec.h
@@ -18,6 +18,9 @@
 #ifndef __ASM_EXEC_H
 #define __ASM_EXEC_H
 
+#include <linux/sched.h>
+
 extern unsigned long arch_align_stack(unsigned long sp);
+void uao_thread_switch(struct task_struct *next);
 
 #endif	/* __ASM_EXEC_H */
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -49,6 +49,7 @@
 #include <asm/alternative.h>
 #include <asm/compat.h>
 #include <asm/cacheflush.h>
+#include <asm/exec.h>
 #include <asm/fpsimd.h>
 #include <asm/mmu_context.h>
 #include <asm/processor.h>
@@ -303,7 +304,7 @@ static void tls_thread_switch(struct tas
 }
 
 /* Restore the UAO state depending on next's addr_limit */
-static void uao_thread_switch(struct task_struct *next)
+void uao_thread_switch(struct task_struct *next)
 {
 	if (IS_ENABLED(CONFIG_ARM64_UAO)) {
 		if (task_thread_info(next)->addr_limit == KERNEL_DS)
--- a/arch/arm64/kernel/suspend.c
+++ b/arch/arm64/kernel/suspend.c
@@ -1,8 +1,11 @@
 #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/exec.h>
 #include <asm/pgtable.h>
 #include <asm/memory.h>
 #include <asm/mmu_context.h>
@@ -48,6 +51,14 @@ void notrace __cpu_suspend_exit(void)
 	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));
+	uao_thread_switch(current);
+
+	/*
 	 * Restore HW breakpoint registers to sane values
 	 * before debug exceptions are possibly reenabled
 	 * through local_dbg_restore.

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[PATCH 4.8 00/35] 4.8.13-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-07 08:10 +0100
  [PATCH 4.8 16/35] PCI: Export pcie_find_root_port Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-07 08:10 +0100
  [PATCH 4.8 11/35] ovl: fix d_real() for stacked fs Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-07 08:10 +0100
  [PATCH 4.8 01/35] libata-scsi: Fixup ata_gen_passthru_sense() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-07 08:10 +0100
  [PATCH 4.8 25/35] drm/radeon: fix check for port PM availability Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-07 08:10 +0100
  [PATCH 4.8 14/35] rcu: Fix soft lockup for rcu_nocb_kthread Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-07 08:10 +0100
  [PATCH 4.8 21/35] drm/i915: drop the struct_mutex when wedged or trying to reset Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-07 08:10 +0100
  [PATCH 4.8 02/35] scsi: hpsa: use bus 3 for legacy HBA devices Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-07 08:10 +0100
  [PATCH 4.8 23/35] drm/radeon: fix power state when port pm is unavailable (v2) Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-07 08:10 +0100
  [PATCH 4.8 26/35] arm64: dts: juno: fix cluster sleep state entry latency on all SoC versions Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-07 08:10 +0100
  [PATCH 4.8 07/35] thp: fix corner case of munlock() of PTE-mapped THPs Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-07 08:20 +0100
  [PATCH 4.8 10/35] mm: fix false-positive WARN_ON() in truncate/invalidate for hugetlb Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-07 08:20 +0100
  [PATCH 4.8 29/35] drm/mediatek: fix null pointer dereference Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-07 08:20 +0100
  [PATCH 4.8 08/35] zram: fix unbalanced idr management at hot removal Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-07 08:20 +0100
  [PATCH 4.8 35/35] arm64: suspend: Reconfigure PSTATE after resume from idle Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-07 08:20 +0100
  [PATCH 4.8 34/35] arm64: mm: Set PSTATE.PAN from the cpu_enable_pan() call Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-07 08:20 +0100
  [PATCH 4.8 04/35] ARC: mm: PAE40: Fix crash at munmap Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-07 08:20 +0100
  [PATCH 4.8 24/35] drm/amdgpu: fix check for port PM availability Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-07 08:20 +0100
  [PATCH 4.8 20/35] drm/i915: Dont touch NULL sg on i915_gem_object_get_pages_gtt() error Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-07 08:20 +0100
  [PATCH 4.8 05/35] ARC: Dont use "+l" inline asm constraint Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-07 08:20 +0100
  [PATCH 4.8 12/35] Input: change KEY_DATA from 0x275 to 0x277 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-07 08:20 +0100
  [PATCH 4.8 30/35] perf/x86: Restore TASK_SIZE check on frame pointer Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-07 08:20 +0100
  [PATCH 4.8 28/35] pwm: Fix device reference leak Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-07 08:20 +0100
  [PATCH 4.8 03/35] scsi: libfc: fix seconds_since_last_reset miscalculation Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-07 08:20 +0100
  [PATCH 4.8 32/35] batman-adv: Detect missing primaryif during tp_send as error Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-07 08:20 +0100
  [PATCH 4.8 33/35] arm64: cpufeature: Schedule enable() calls instead of calling them via IPI Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-07 08:20 +0100
  [PATCH 4.8 09/35] kasan: update kasan_global for gcc 7 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-07 08:20 +0100
  Re: [PATCH 4.8 00/35] 4.8.13-stable review Guenter Roeck <linux@roeck-us.net> - 2016-12-07 17:10 +0100
    Re: [PATCH 4.8 00/35] 4.8.13-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-08 17:30 +0100
  Re: [PATCH 4.8 00/35] 4.8.13-stable review Shuah Khan <shuah.kh@samsung.com> - 2016-12-07 19:20 +0100
    Re: [PATCH 4.8 00/35] 4.8.13-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-08 17:30 +0100
  Re: [PATCH 4.8 00/35] 4.8.13-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-08 17:30 +0100

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