Re: [PATCH v21 7/9] arm64: Block hibernate and kexec while RMM is active
From: Suzuki K Poulose
Date: Thu Oct 01 2026 - 07:39:54 EST
On 01/10/2026 12:05, Catalin Marinas wrote:
On Thu, Oct 01, 2026 at 09:45:53AM +0100, Suzuki K Poulose wrote:
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.
I would mention that this adds a new arch_hibernation_available() hook
called from hibernation_available(), otherwise the hibernation
maintainers may not realise why they've been cc'ed.
Alternatively, just introduce the hook as a separate patch without any
arch code.
I will go for this approach, adding the hook in a prep patch and then
the arm64 version with kexec changes.
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();
+}
For now, I would keep is_rmm_active() only in here as not to change the
behaviour for pKVM. "disk" would disappear from /sys/power/state with
this patch. I think it's the correct thing to do for pKVM as well but we
can discuss this separately once this goes in (I also think pKVM using
cpus_are_stuck_in_kernel() is a bit of a bodge but it's a handy hook
called in the right places).
I was in double mind about this. Yes, I agree, makes sense to deal the
pKVM case separately.
+
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();
}
With the comments above addressed:
Reviewed-by: Catalin Marinas <catalin.marinas@xxxxxxx>
Thank you!
Suzuki