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>

diff --git a/arch/arm64/kernel/suspend.c b/arch/arm64/kernel/suspend.c
index 1095aa483a1c28e5387b23895c14d7a1746268a3..00c1372bf57ba19e74d6bb87cc0fdc8e6ead8837 100644 (file)
--- 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>
@@ -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