[PATCH v31 02/12] arm64: limit memory regions based on DT property, usable-memory-range

On Wed, Feb 01, 2017 at 03:07:00PM +0000, Mark Rutland wrote:

Hi,

On Wed, Feb 01, 2017 at 09:46:21PM +0900, AKASHI Takahiro wrote:

quoted

+static int __init early_init_dt_scan_usablemem(unsigned long node,
+		const char *uname, int depth, void *data)
+{
+	struct memblock_region *usablemem = (struct memblock_region *)data;

Nit: unnecessary cast.

OK

quoted

+	const __be32 *reg;
+	int len;
+
+	usablemem->size = 0;

Could we please lift this assignment/initialisation into the caller...

quoted

+
+	if (depth != 1 || strcmp(uname, "chosen") != 0)
+		return 0;
+
+	reg = of_get_flat_dt_prop(node, "linux,usable-memory-range", &len);
+	if (!reg || (len < (dt_root_addr_cells + dt_root_size_cells)))
+		return 1;
+
+	usablemem->base = dt_mem_next_cell(dt_root_addr_cells, &reg);
+	usablemem->size = dt_mem_next_cell(dt_root_size_cells, &reg);
+
+	return 1;
+}
+
+static void __init fdt_enforce_memory_region(void)
+{
+	struct memblock_region reg;

... e.g. have:

	struct memblock_region reg = {
		.size = 0,
	};

Sure

That saves us from making unnecessary assignments to the size field, and
makes it clear that reg.size has definitely been initialised, regardless
of what of_scan_flat_dt() happens to do.

With that:

Acked-by: Mark Rutland <mark.rutland@arm.com>

Thanks,
-Takahiro AKASHI

Thanks,
Mark.

quoted

+
+	of_scan_flat_dt(early_init_dt_scan_usablemem, &reg);
+
+	if (reg.size)
+		memblock_cap_memory_range(reg.base, reg.size);
+}
+
 void __init arm64_memblock_init(void)
 {
 	const s64 linear_region_size = -(s64)PAGE_OFFSET;
 
+	/* Handle linux,usable-memory-range property */
+	fdt_enforce_memory_region();
+
 	/*
 	 * Ensure that the linear region takes up exactly half of the kernel
 	 * virtual address space. This way, we can distinguish a linear address
-- 
2.11.0