[PATCH v22 08/10] arm64: Block hibernate and kexec while RMM is active

[Suzuki K Poulose <suzuki.poulose@arm.com>]

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.
Also, on the resume path, if the RMM is active, there could be delegated
granules and overwriting them is fatal.

Disable both kexec and hiberation while the RMM is active.

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
---
Changes since v21:
 - Drop cpus_are_stuck_in_kernel() from arch_hibernation_available()
 - Split arch_hibernation_available() hook as a separate patch
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 +++++++++++
 2 files changed, 25 insertions(+)

diff --git a/arch/arm64/kernel/hibernate.c b/arch/arm64/kernel/hibernate.c
index 7bf1174277772..327e62a259aa7 100644
--- a/arch/arm64/kernel/hibernate.c
+++ b/arch/arm64/kernel/hibernate.c
@@ -10,6 +10,8 @@
  * Copyright (C) 2006 Rafael J. Wysocki <rjw@sisk.pl>
  */
 #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 !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;
 }
 
-- 
2.43.0