The version of PSCI that the kernel should use to communicate with
firmware is typically obtained from probing PSCI_VERSION. However, that
doesn't work for PSCI v0.1 where the host gets the information from
DT/ACPI, or if PSCI is not supported / was disabled.

KVM's host PSCI proxy needs to be configured with the same version
used by the host driver. Expose the PSCI version used by the host
with a read-only accessor.

Signed-off-by: David Brazdil <redacted>
---
 drivers/firmware/psci/psci.c | 11 +++++++++++
 include/linux/psci.h         |  8 ++++++++
 2 files changed, 19 insertions(+)

diff --git a/drivers/firmware/psci/psci.c 

b/drivers/firmware/psci/psci.c
index 00af99b6f97c..bc1b2d60fdbf 100644

--- a/drivers/firmware/psci/psci.c
+++ b/drivers/firmware/psci/psci.c

@@ -49,6 +49,13 @@ static int resident_cpu = -1;
 struct psci_operations psci_ops;
 static enum arm_smccc_conduit psci_conduit = SMCCC_CONDUIT_NONE;

+static int driver_version = PSCI_VERSION(0, 0);
+
+int psci_driver_version(void)
+{
+	return driver_version;
+}
+
 bool psci_tos_resident_on(int cpu)
 {
 	return cpu == resident_cpu;

@@ -461,6 +468,8 @@ static int __init psci_probe(void)
 		return -EINVAL;
 	}

+	driver_version = ver;
+
 	psci_0_2_set_functions();

 	psci_init_migrate();

@@ -514,6 +523,8 @@ static int __init psci_0_1_init(struct device_node 

*np)

 	pr_info("Using PSCI v0.1 Function IDs from DT\n");

+	driver_version = PSCI_VERSION(0, 1);
+
 	if (!of_property_read_u32(np, "cpu_suspend", &id)) {
 		psci_function_id[PSCI_FN_CPU_SUSPEND] = id;
 		psci_ops.cpu_suspend = psci_cpu_suspend;

diff --git a/include/linux/psci.h b/include/linux/psci.h
index 2a1bfb890e58..5b5dcf176aa6 100644
--- a/include/linux/psci.h
+++ b/include/linux/psci.h

@@ -21,6 +21,14 @@ bool psci_power_state_is_valid(u32 state);
 int psci_set_osi_mode(bool enable);
 bool psci_has_osi_support(void);

+/**
+ * The version of the PSCI specification followed by the driver.
+ * This is equivalent to calling PSCI_VERSION except:
+ *   (a) it also works for PSCI v0.1, which does not support 

PSCI_VERSION, and
+ *   (b) it is set to v0.0 if the PSCI driver was not initialized.
+ */
+int psci_driver_version(void);
+
 struct psci_operations {
 	u32 (*get_version)(void);
 	int (*cpu_suspend)(u32 state, unsigned long entry_point);