[RFC PATCH v2 5/7] pmpool: Update device tree on kexec

[Stanislav Kinsburskii <skinsburskii@linux.microsoft.com>]

From: Stanislav Kinsburskii <stanislav.kinsburskii@gmail.com>

Introduce a pmpool kexec fdt notifier that enables pmpool to pass its
metadata, including the bitmap address, to the new kernel during kexec.

Signed-off-by: Stanislav Kinsburskii <skinsburskii@linux.microsoft.com>
---
 mm/Kconfig  |    1 +
 mm/pmpool.c |   64 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 64 insertions(+), 1 deletion(-)

diff --git a/mm/Kconfig b/mm/Kconfig
index e7c10094fb10..1eefdd4c82ba 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -925,6 +925,7 @@ config CMA_AREAS
 config PMPOOL
 	bool "Persistent memory pool support"
 	select CMA
+	select LIBFDT
 	help
 	  This option adds support for CMA-based persistent memory pool
 	  feature, which provides pages allocation and freeing from a set of
diff --git a/mm/pmpool.c b/mm/pmpool.c
index 12a8cac75558..f2173db782d6 100644
--- a/mm/pmpool.c
+++ b/mm/pmpool.c
@@ -6,6 +6,7 @@
 #include <linux/cma.h>
 #include <linux/io.h>
 #include <linux/kexec.h>
+#include <linux/libfdt.h>
 #include <linux/memblock.h>
 #include <linux/mm.h>
 #include <linux/pmpool.h>
@@ -58,6 +59,59 @@ static int __init default_pmpool_fixup_cma(void)
 }
 postcore_initcall(default_pmpool_fixup_cma);
 
+static int pmpool_fdt_update(struct notifier_block *nb, unsigned long val,
+			     void *data)
+{
+	void *fdt = data;
+	int node, status;
+
+	if (!fdt)
+		goto err;
+
+	node = fdt_subnode_offset(fdt, 0, "chosen");
+	if (node < 0) {
+		node = fdt_add_subnode(fdt, 0, "chosen");
+		if (node < 0)
+			goto err;
+	}
+
+	node = fdt_add_subnode(fdt, node, "default_pmpool");
+	if (node == -FDT_ERR_EXISTS)
+		return 0;
+	if (node < 0)
+		goto err;
+
+	status = fdt_setprop(fdt, node, "compatible",
+			     "pmpool", sizeof("pmpool"));
+	if (status)
+		goto err;
+
+	status = fdt_setprop_u64(fdt, node, "bitmap",
+				 virt_to_phys(default_pmpool->cma->bitmap));
+	if (status)
+		goto err;
+
+	status = fdt_setprop_u64(fdt, node, "size",
+				 default_pmpool->cma->count << PAGE_SHIFT);
+	if (status)
+		goto err;
+
+	status = fdt_setprop_u64(fdt, node, "base",
+				 default_pmpool->cma->base_pfn << PAGE_SHIFT);
+	if (status)
+		goto err;
+
+	return NOTIFY_DONE;
+
+err:
+	pr_err("failed to update fdt\n");
+	return NOTIFY_DONE;
+}
+
+static struct notifier_block pmpool_kexec_fdt_nb = {
+	.notifier_call  = pmpool_fdt_update,
+};
+
 static int __init parse_pmpool_opt(char *str)
 {
 	static struct pmpool pmpool;
@@ -80,10 +134,16 @@ static int __init parse_pmpool_opt(char *str)
 		return 0;
 	}
 
+	err = register_kexec_fdt_notifier(&pmpool_kexec_fdt_nb);
+	if (err) {
+		pr_err("failed to register kexec fdt notifier: %d\n", err);
+		goto free_memblock;
+	}
+
 	err = cma_init_reserved_mem(base, size, 0, "pmpool", &pmpool.cma);
 	if (err) {
 		pr_err("failed to initialize CMA: %d\n", err);
-		goto free_memblock;
+		goto notifier_unregister;
 	}
 
 	pr_info("default memory pool is created: %#llx-%#llx\n",
@@ -93,6 +153,8 @@ static int __init parse_pmpool_opt(char *str)
 
 	return 0;
 
+notifier_unregister:
+	unregister_kexec_fdt_notifier(&pmpool_kexec_fdt_nb);
 free_memblock:
 	memblock_phys_free(base, size);
 	return 0;