Re: [PATCH v19 5/7] firmware: arm_rmm: Activate the RMM

firmware: rmm: Deactivate RMM at reboot

Deactivate the RMM at system shutdown. This would allow a normal kexec to
cleanup the state and boot into a new kernel gracefully.

Kdump kernels need not worry about an active RMM, as long as it can
handle the GPF on access to the Delegated granules.

Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
---
 arch/arm64/kernel/machine_kexec.c |  2 +
 drivers/firmware/arm_rmm/rmi.c    | 63 ++++++++++++++++++++++++++++++-
 include/linux/arm-rmi-cmds.h      | 10 +++++
 3 files changed, 73 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kernel/machine_kexec.c

b/arch/arm64/kernel/machine_kexec.c
index 8f9bc2327dc85..8f16f92a5d389 100644

--- a/arch/arm64/kernel/machine_kexec.c
+++ b/arch/arm64/kernel/machine_kexec.c

@@ -6,6 +6,7 @@
  * Copyright (C) Huawei Futurewei Technologies.
  */

+#include <linux/arm-rmi-cmds.h>
 #include <linux/interrupt.h>
 #include <linux/irq.h>
 #include <linux/kernel.h>

@@ -171,6 +172,7 @@ void machine_kexec(struct kimage *kimage)
 	BUG_ON(!in_kexec_crash && (stuck_cpus || (num_online_cpus() > 1)));
 	WARN(in_kexec_crash && (stuck_cpus || smp_crash_stop_failed()),
 		"Some CPUs may be stale, kdump will be unreliable.\n");
+	WARN(!in_kexec_crash && is_rmm_active(), "RMM is active, kexec will be

unreliable.\n");

 	pr_info("Bye!\n");

diff --git a/drivers/firmware/arm_rmm/rmi.c b/drivers/firmware/arm_rmm/rmi.c
index 51343e9d5c2a9..5b695f3155b1c 100644
--- a/drivers/firmware/arm_rmm/rmi.c
+++ b/drivers/firmware/arm_rmm/rmi.c

@@ -7,6 +7,7 @@
 #include <linux/memblock.h>
 #include <linux/memory.h>
 #include <linux/arm-rmi-cmds.h>
+#include <linux/reboot.h>
 #include <linux/slab.h>

 #include <asm/memory.h>

@@ -15,6 +16,13 @@
 /* RMM v2.0 defines RmiFeatureRegister0 to RmiFeatureRegister4. */
 static unsigned long rmi_feat_reg_cache[5] __ro_after_init;
 static bool arm64_rmi_is_available;
+static bool arm64_rmm_active;
+
+bool is_rmm_active(void)
+{
+	return arm64_rmm_active;
+}
+EXPORT_SYMBOL_GPL(is_rmm_active);

 /**
  * rmi_granule_range_undelegate() - Undelegate a range of granules

@@ -1017,6 +1025,53 @@ bool is_rmi_available(void)
 }
 EXPORT_SYMBOL_GPL(is_rmi_available);

+static int rmi_rmm_deactivate(struct rmi_sro_state *sro)
+{
+	int ret;
+
+	if (!READ_ONCE(arm64_rmm_active))
+		return 0;
+
+	ret = WARN_ON(rmi_sro_memxfer_cmd(sro, GFP_KERNEL, SMC_RMI_RMM_DEACTIVATE));
+	if (ret)
+		return ret;
+
+	WRITE_ONCE(arm64_rmm_active, false);
+	WRITE_ONCE(arm64_rmi_is_available, false);
+
+	return ret;
+}
+
+static int rmi_reboot_notifier(struct notifier_block *nb,
+			       unsigned long action, void *data)
+{
+	int ret;
+
+	switch (action) {
+	case SYS_RESTART:
+	case SYS_HALT:
+	case SYS_POWER_OFF:
+		break;
+	default:
+		return NOTIFY_DONE;
+	}
+
+	struct rmi_sro_state *sro __free(kfree) = kmalloc_obj(*sro);
+
+	if (!sro)
+		return -ENOMEM;

+
+	ret = rmi_rmm_deactivate(sro);
+	if (ret)
+		pr_emerg("RMM Deactivation failed: %d\n", ret);
+
+	return NOTIFY_DONE;
+}
+
+static struct notifier_block rmi_reboot_nb = {
+	.notifier_call = rmi_reboot_notifier,
+};