arm64: Use SYSTEM_OFF2 PSCI call to power off for hibernate

The PSCI v1.3 specification adds support for a SYSTEM_OFF2 function
which is analogous to ACPI S4 state. This will allow hosting
environments to determine that a guest is hibernated rather than just
powered off, and handle that state appropriately on subsequent launches.

Since commit 60c0d45a7f7a ("efi/arm64: use UEFI for system reset and
poweroff") the EFI shutdown method is deliberately preferred over PSCI
or other methods. So register a SYS_OFF_MODE_POWER_OFF handler which
*only* handles the hibernation, leaving the original PSCI SYSTEM_OFF as
a last resort via the legacy pm_power_off function pointer.

The hibernation code already exports a system_entering_hibernation()
function which is be used by the higher-priority handler to check for
hibernation. That existing function just returns the value of a static
boolean variable from hibernate.c, which was previously only set in the
hibernation_platform_enter() code path. Set the same flag in the simpler
code path around the call to kernel_power_off() too.

An alternative way to hook SYSTEM_OFF2 into the hibernation code would
be to register a platform_hibernation_ops structure with an ->enter()
method which makes the new SYSTEM_OFF2 call. But that would have the
unwanted side-effect of making hibernation take a completely different
code path in hibernation_platform_enter(), invoking a lot of special dpm
callbacks.

Another option might be to add a new SYS_OFF_MODE_HIBERNATE mode, with
fallback to SYS_OFF_MODE_POWER_OFF. Or to use the sys_off_data to
indicate whether the power off is for hibernation.

But this version works and is relatively simple.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Acked-by: Rafael J. Wysocki <rafael@kernel.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20241019172459.2241939-7-dwmw2@infradead.org
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>

diff --git a/drivers/firmware/psci/psci.c b/drivers/firmware/psci/psci.c
index 2328ca5..a1ebbe9 100644 (file)
--- a/drivers/firmware/psci/psci.c
+++ b/drivers/firmware/psci/psci.c
@@ -78,6 +78,7 @@ struct psci_0_1_function_ids get_psci_0_1_function_ids(void)
 
 static u32 psci_cpu_suspend_feature;
 static bool psci_system_reset2_supported;
+static bool psci_system_off2_hibernate_supported;
 
 static inline bool psci_has_ext_power_state(void)
 {
@@ -333,6 +334,36 @@ static void psci_sys_poweroff(void)
        invoke_psci_fn(PSCI_0_2_FN_SYSTEM_OFF, 0, 0, 0);
 }
 
+#ifdef CONFIG_HIBERNATION
+static int psci_sys_hibernate(struct sys_off_data *data)
+{
+       /*
+        * If no hibernate type is specified SYSTEM_OFF2 defaults to selecting
+        * HIBERNATE_OFF.
+        *
+        * There are hypervisors in the wild that do not align with the spec and
+        * reject calls that explicitly provide a hibernate type. For
+        * compatibility with these nonstandard implementations, pass 0 as the
+        * type.
+        */
+       if (system_entering_hibernation())
+               invoke_psci_fn(PSCI_FN_NATIVE(1_3, SYSTEM_OFF2), 0, 0, 0);
+       return NOTIFY_DONE;
+}
+
+static int __init psci_hibernate_init(void)
+{
+       if (psci_system_off2_hibernate_supported) {
+               /* Higher priority than EFI shutdown, but only for hibernate */
+               register_sys_off_handler(SYS_OFF_MODE_POWER_OFF,
+                                        SYS_OFF_PRIO_FIRMWARE + 2,
+                                        psci_sys_hibernate, NULL);
+       }
+       return 0;
+}
+subsys_initcall(psci_hibernate_init);
+#endif
+
 static int psci_features(u32 psci_func_id)
 {
        return invoke_psci_fn(PSCI_1_0_FN_PSCI_FEATURES,
@@ -364,6 +395,7 @@ static const struct {
        PSCI_ID_NATIVE(1_1, SYSTEM_RESET2),
        PSCI_ID(1_1, MEM_PROTECT),
        PSCI_ID_NATIVE(1_1, MEM_PROTECT_CHECK_RANGE),
+       PSCI_ID_NATIVE(1_3, SYSTEM_OFF2),
 };
 
 static int psci_debugfs_read(struct seq_file *s, void *data)
@@ -525,6 +557,18 @@ static void __init psci_init_system_reset2(void)
                psci_system_reset2_supported = true;
 }
 
+static void __init psci_init_system_off2(void)
+{
+       int ret;
+
+       ret = psci_features(PSCI_FN_NATIVE(1_3, SYSTEM_OFF2));
+       if (ret < 0)
+               return;
+
+       if (ret & PSCI_1_3_OFF_TYPE_HIBERNATE_OFF)
+               psci_system_off2_hibernate_supported = true;
+}
+
 static void __init psci_init_system_suspend(void)
 {
        int ret;
@@ -655,6 +699,7 @@ static int __init psci_probe(void)
                psci_init_cpu_suspend();
                psci_init_system_suspend();
                psci_init_system_reset2();
+               psci_init_system_off2();
                kvm_init_hyp_services();
        }
 

diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
index e35829d..1f87aa0 100644 (file)
--- a/kernel/power/hibernate.c
+++ b/kernel/power/hibernate.c
@@ -685,8 +685,11 @@ static void power_down(void)
                }
                fallthrough;
        case HIBERNATION_SHUTDOWN:
-               if (kernel_can_power_off())
+               if (kernel_can_power_off()) {
+                       entering_platform_hibernation = true;
                        kernel_power_off();
+                       entering_platform_hibernation = false;
+               }
                break;
        }
        kernel_halt();