[PATCH 06/15] arm64: Add KHO support

@@ -1501,6 +1501,18 @@ config ARCH_SUPPORTS_CRASH_DUMP
 config ARCH_HAS_GENERIC_CRASHKERNEL_RESERVATION
 	def_bool CRASH_CORE
 
+config KEXEC_KHO
+	bool "kexec handover"
+	depends on KEXEC
+	select MEMBLOCK_SCRATCH
+	select LIBFDT
+	select CMA
+	help
+	  Allow kexec to hand over state across kernels by generating and
+	  passing additional metadata to the target kernel. This is useful
+	  to keep data or state alive across the kexec. For this to work,
+	  both source and target kernels need to have this option enabled.
+
 config TRANS_TABLE
 	def_bool y
 	depends on HIBERNATION || KEXEC_CORE

@@ -346,6 +346,8 @@ void __init __no_sanitize_address setup_arch(char **cmdline_p)
 
 	paging_init();
 
+	kho_reserve_mem();
+
 	acpi_table_upgrade();
 
 	/* Parse the ACPI tables for possible boot-time configuration */

@@ -358,6 +358,8 @@ void __init bootmem_init(void)
 	 */
 	arch_reserve_crashkernel();
 
+	kho_reserve();
+
 	memblock_dump_all();
 }
 

@@ -386,6 +388,12 @@ void __init mem_init(void)
 	/* this will put all unused low memory onto the freelists */
 	memblock_free_all();
 
+	/*
+	 * Now that all KHO pages are marked as reserved, let's flip them back
+	 * to normal pages with accurate refcount.
+	 */
+	kho_populate_refcount();
+
 	/*
 	 * Check boundaries twice: Some fundamental inconsistencies can be
 	 * detected at build time already.

@@ -1006,6 +1006,44 @@ 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
+ */
+void __init early_init_dt_check_kho(void)
+{
+#ifdef CONFIG_KEXEC_KHO
+	unsigned long node = chosen_node_offset;
+	u64 kho_start, scratch_start, scratch_size, mem_start, mem_size;
+	const __be32 *p;
+	int l;
+
+	if ((long)node < 0)
+		return;
+
+	p = of_get_flat_dt_prop(node, "linux,kho-dt", &l);
+	if (l != (dt_root_addr_cells + dt_root_size_cells) * sizeof(__be32))
+		return;
+
+	kho_start = 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);
+
+	p = of_get_flat_dt_prop(node, "linux,kho-mem", &l);
+	if (l != (dt_root_addr_cells + dt_root_size_cells) * sizeof(__be32))
+		return;
+
+	mem_start = dt_mem_next_cell(dt_root_addr_cells, &p);
+	mem_size = dt_mem_next_cell(dt_root_addr_cells, &p);
+
+	kho_populate(kho_start, scratch_start, scratch_size, mem_start, mem_size);
+#endif
+}
+
 #ifdef CONFIG_SERIAL_EARLYCON
 
 int __init early_init_dt_scan_chosen_stdout(void)

@@ -1304,6 +1342,9 @@ 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 *params)

@@ -264,6 +264,37 @@ static inline int setup_ima_buffer(const struct kimage *image, void *fdt,
 }
 #endif /* CONFIG_IMA_KEXEC */
 
+static int kho_add_chosen(const struct kimage *image, void *fdt, int chosen_node)
+{
+	int ret = 0;
+
+#ifdef CONFIG_KEXEC_KHO
+	if (!image->kho.dt.buffer || !image->kho.mem_cache.buffer)
+		goto out;
+
+	pr_debug("Adding kho metadata to DT");
+
+	ret = fdt_appendprop_addrrange(fdt, 0, chosen_node, "linux,kho-dt",
+				       image->kho.dt.mem, image->kho.dt.memsz);
+	if (ret)
+		goto out;
+
+	ret = fdt_appendprop_addrrange(fdt, 0, chosen_node, "linux,kho-scratch",
+				       kho_scratch_phys, kho_scratch_len);
+	if (ret)
+		goto out;
+
+	ret = fdt_appendprop_addrrange(fdt, 0, chosen_node, "linux,kho-mem",
+				       image->kho.mem_cache.mem,
+				       image->kho.mem_cache.bufsz);
+	if (ret)
+		goto out;
+
+out:
+#endif
+	return ret;
+}
+
 /*
  * of_kexec_alloc_and_setup_fdt - Alloc and setup a new Flattened Device Tree
  *

@@ -412,6 +443,11 @@ void *of_kexec_alloc_and_setup_fdt(const struct kimage *image,
 		}
 	}
 
+	/* Add kho metadata if this is a KHO image */
+	ret = kho_add_chosen(image, fdt, chosen_node);
+	if (ret)
+		goto out;
+
 	/* add bootargs */
 	if (cmdline) {
 		ret = fdt_setprop_string(fdt, chosen_node, "bootargs", cmdline);