[PATCH v21 7/9] arm64: Block hibernate and kexec while RMM is active

[Suzuki K Poulose]

RMM can be deactivated only after all delegated granules have been
reclaimed. If a new kernel is entered while any granules remain in the
Realm PAS, accesses to that memory can raise a Granule Protection Fault
and be fatal to the new kernel.

Crash kexec/kdump needs separate handling. It can be supported only once
the crash kernel can tolerate delegated memory inherited from the primary
kernel. i.e., be able to read the pages safely and fixup the GPF. Until
then disable the kexec completely.

Hibernate has a similar problem. The image cannot be safely saved for
delegated pages, as the RMM doesn't support exporting the pages.

Disable both kexec and hiberation while the RMM is active.

Cc: "Rafael J. Wysocki" <rafael@xxxxxxxxxx>
Cc: Len Brown <lenb@xxxxxxxxxx>
Cc: Pavel Machek <pavel@xxxxxxxxxx>
Cc: linux-pm@xxxxxxxxxxxxxxx
Signed-off-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
---
Changes since v20:
 - Add arch_hibernation_available() hook for archs to have a say and drop the
   other checks.
Changes since v19:
 - New patch to disable kexec and hibernation with RMM
---
 arch/arm64/kernel/hibernate.c     | 14 ++++++++++++++
 arch/arm64/kernel/machine_kexec.c | 11 +++++++++++
 include/linux/suspend.h           |  1 +
 kernel/power/hibernate.c          |  8 +++++++-
 4 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kernel/hibernate.c b/arch/arm64/kernel/hibernate.c
index 7bf1174277772..08e03d24b93a8 100644
--- a/arch/arm64/kernel/hibernate.c
+++ b/arch/arm64/kernel/hibernate.c
@@ -10,6 +10,8 @@
  * Copyright (C) 2006 Rafael J. Wysocki <rjw@xxxxxxx>
  */
 #define pr_fmt(x) "hibernate: " x
+
+#include <linux/arm-rmi-cmds.h>
 #include <linux/cpu.h>
 #include <linux/kvm_host.h>
 #include <linux/pm.h>
@@ -105,6 +107,18 @@ void notrace restore_processor_state(void)
 {
 }
 
+bool arch_hibernation_available(void)
+{
+	/*
+	 * If we have activated the RMM, there could be pages that are
+	 * delegated to the RMM. Trying to save them to the image will be fatal.
+	 * Also, we donate pages to the RMM at activation and restoring data
+	 * to those pages are going to be fatal.
+	 * Hence, disable the hibernation when the RMM is active
+	 */
+	return !cpus_are_stuck_in_kernel() && !is_rmm_active();
+}
+
 int arch_hibernation_header_save(void *addr, unsigned int max_size)
 {
 	struct arch_hibernate_hdr *hdr = addr;
diff --git a/arch/arm64/kernel/machine_kexec.c b/arch/arm64/kernel/machine_kexec.c
index 8f9bc2327dc85..48f343704cb54 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>
@@ -59,6 +60,16 @@ int machine_kexec_prepare(struct kimage *kimage)
 		return -EBUSY;
 	}
 
+	/*
+	 * We will be able to allow kdump to proceed, once we have the support
+	 * for handling GPF from vmcore accesses to delegated pages. Until then
+	 * block kexec completely.
+	 */
+	if (is_rmm_active()) {
+		pr_err("Can't kexec: RMM is active.\n");
+		return -EBUSY;
+	}
+
 	return 0;
 }
 
diff --git a/include/linux/suspend.h b/include/linux/suspend.h
index b02876f1ae38a..a3815027773c5 100644
--- a/include/linux/suspend.h
+++ b/include/linux/suspend.h
@@ -401,6 +401,7 @@ int hibernate_quiet_exec(int (*func)(void *data), void *data);
 int hibernate_resume_nonboot_cpu_disable(void);
 int arch_hibernation_header_save(void *addr, unsigned int max_size);
 int arch_hibernation_header_restore(void *addr);
+bool arch_hibernation_available(void);
 
 #else /* CONFIG_HIBERNATION */
 static inline void register_nosave_region(unsigned long b, unsigned long e) {}
diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
index d2479c69d71a4..9d9d53828542f 100644
--- a/kernel/power/hibernate.c
+++ b/kernel/power/hibernate.c
@@ -106,11 +106,17 @@ bool hibernation_in_progress(void)
 	return !atomic_read(&hibernate_atomic);
 }
 
+__weak bool arch_hibernation_available(void)
+{
+	return true;
+}
+
 bool hibernation_available(void)
 {
 	return nohibernate == 0 &&
 		!security_locked_down(LOCKDOWN_HIBERNATION) &&
-		!secretmem_active() && !cxl_mem_active();
+		!secretmem_active() && !cxl_mem_active() &&
+		arch_hibernation_available();
 }
 
 /**
-- 
2.43.0