arm64: suspend: rely on daif helpers to handle PMR

Commit 77345ef70445 ("arm64: suspend: Use cpuidle context helpers
in cpu_suspend()") added cpuidle helpers to handle PMR manipulation
and restoration to ensure that the CPU receives interrupts when suspended
and pseudo-NMIs are enabled.

However, those helpers are called in between a pair of `local_daif_save()`
and `local_daif_restore()`, which already configure the PMR as expected.
Effectively, `arm_cpuidle_save_irq_context()` is a no-op here,
even when using pseudo-NMIs, and `arm_cpuidle_restore_irq_context()`
would not restore proper interrupt masking configuration early enough
if there were unexpected changes during suspend or resume.
(This can be observed with Trusted Firmware A (TF-A) at EL3 handling
suspend through PSCI. Even though it should not be the case, TF-A can
reset `ICC_PMR_EL1` during CPU_SUSPEND, thus resuming the kernel
with an inconsistent priority mask value on hardware implementing
more than the minimum number of priority levels, such as Morello.)

Thus : remove the cpuidle context helpers as they do not do anything,
but keep the comment mentioning the need for interrupts to reach the CPU
if we are using pseudo-NMIs.

Signed-off-by: Ada Couprie Diaz <ada.coupriediaz@arm.com>
Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
Reviewed-by: Jinjie Ruan <ruanjinjie@huawei.com>
Signed-off-by: Will Deacon <will@kernel.org>

diff --git a/arch/arm64/kernel/suspend.c b/arch/arm64/kernel/suspend.c
index eaaff94..c41724a 100644 (file)
--- a/arch/arm64/kernel/suspend.c
+++ b/arch/arm64/kernel/suspend.c
@@ -99,7 +99,6 @@ int cpu_suspend(unsigned long arg, int (*fn)(unsigned long))
        int ret = 0;
        unsigned long flags;
        struct sleep_stack_data state;
-       struct arm_cpuidle_irq_context context;
 
        /*
         * Some portions of CPU state (e.g. PSTATE.{PAN,DIT}) are initialized
@@ -121,6 +120,9 @@ int cpu_suspend(unsigned long arg, int (*fn)(unsigned long))
         * Strictly speaking the trace_hardirqs_off() here is superfluous,
         * hardirqs should be firmly off by now. This really ought to use
         * something like raw_local_daif_save().
+        *
+        * This also unmasks interrupts in PMR in order to reliably
+        * resume if we're using pseudo-NMIs.
         */
        flags = local_daif_save();
 
@@ -131,12 +133,6 @@ int cpu_suspend(unsigned long arg, int (*fn)(unsigned long))
         */
        pause_graph_tracing();
 
-       /*
-        * Switch to using DAIF.IF instead of PMR in order to reliably
-        * resume if we're using pseudo-NMIs.
-        */
-       arm_cpuidle_save_irq_context(&context);
-
        ct_cpuidle_enter();
 
        if (__cpu_suspend_enter(&state)) {
@@ -159,8 +155,6 @@ int cpu_suspend(unsigned long arg, int (*fn)(unsigned long))
                __cpu_suspend_exit();
        }
 
-       arm_cpuidle_restore_irq_context(&context);
-
        unpause_graph_tracing();
 
        /*