arm64: add KHO support

We now have all bits in place to support KHO kexecs.  Add awareness of KHO
in the kexec file as well as boot path for arm64 and adds the respective
kconfig option to the architecture so that it can use KHO successfully.

Changes to the "chosen" node have been sent to
https://github.com/devicetree-org/dt-schema/pull/158.

Link: https://lkml.kernel.org/r/20250509074635.3187114-10-changyuanl@google.com
Signed-off-by: Alexander Graf <graf@amazon.com>
Co-developed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Co-developed-by: Changyuan Lyu <changyuanl@google.com>
Signed-off-by: Changyuan Lyu <changyuanl@google.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Anthony Yznaga <anthony.yznaga@oracle.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Ashish Kalra <ashish.kalra@amd.com>
Cc: Ben Herrenschmidt <benh@kernel.crashing.org>
Cc: Borislav Betkov <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Gowans <jgowans@amazon.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Krzysztof Kozlowski <krzk@kernel.org>
Cc: Marc Rutland <mark.rutland@arm.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Pratyush Yadav <ptyadav@amazon.de>
Cc: Rob Herring <robh@kernel.org>
Cc: Saravana Kannan <saravanak@google.com>
Cc: Stanislav Kinsburskii <skinsburskii@linux.microsoft.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleinxer <tglx@linutronix.de>
Cc: Thomas Lendacky <thomas.lendacky@amd.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 34 insertions, 0 deletions

diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
index aedd0e2dcd89..0edd639898a6 100644
--- a/drivers/of/fdt.c
+++ b/drivers/of/fdt.c
@@ -25,6 +25,7 @@
 #include <linux/serial_core.h>
 #include <linux/sysfs.h>
 #include <linux/random.h>
+#include <linux/kexec_handover.h>
 
 #include <asm/setup.h>  /* for COMMAND_LINE_SIZE */
 #include <asm/page.h>
@@ -875,6 +876,36 @@ void __init early_init_dt_check_for_usable_mem_range(void)
 		memblock_add(rgn[i].base, rgn[i].size);
 }
 
+/**
+ * early_init_dt_check_kho - Decode info required for kexec handover from DT
+ */
+static void __init early_init_dt_check_kho(void)
+{
+	unsigned long node = chosen_node_offset;
+	u64 fdt_start, fdt_size, scratch_start, scratch_size;
+	const __be32 *p;
+	int l;
+
+	if (!IS_ENABLED(CONFIG_KEXEC_HANDOVER) || (long)node < 0)
+		return;
+
+	p = of_get_flat_dt_prop(node, "linux,kho-fdt", &l);
+	if (l != (dt_root_addr_cells + dt_root_size_cells) * sizeof(__be32))
+		return;
+
+	fdt_start = dt_mem_next_cell(dt_root_addr_cells, &p);
+	fdt_size = dt_mem_next_cell(dt_root_addr_cells, &p);
+
+	p = of_get_flat_dt_prop(node, "linux,kho-scratch", &l);
+	if (l != (dt_root_addr_cells + dt_root_size_cells) * sizeof(__be32))
+		return;
+
+	scratch_start = dt_mem_next_cell(dt_root_addr_cells, &p);
+	scratch_size = dt_mem_next_cell(dt_root_addr_cells, &p);
+
+	kho_populate(fdt_start, fdt_size, scratch_start, scratch_size);
+}
+
 #ifdef CONFIG_SERIAL_EARLYCON
 
 int __init early_init_dt_scan_chosen_stdout(void)
@@ -1169,6 +1200,9 @@ void __init early_init_dt_scan_nodes(void)
 
 	/* Handle linux,usable-memory-range property */
 	early_init_dt_check_for_usable_mem_range();
+
+	/* Handle kexec handover */
+	early_init_dt_check_kho();
 }
 
 bool __init early_init_dt_scan(void *dt_virt, phys_addr_t dt_phys)