diff mbox

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

Message ID 20170201124630.6016-1-takahiro.akashi@linaro.org (mailing list archive)
State New, archived
Headers show

Commit Message

AKASHI Takahiro Feb. 1, 2017, 12:46 p.m. UTC 
Crash dump kernel utilizes only a subset of available memory as System RAM.
On arm64 kdump, This memory range is advertized to crash dump kernel via
a device-tree property under /chosen,
   linux,usable-memory-range = <BASE SIZE>

Crash dump kernel reads this property at boot time and calls
memblock_cap_memory_range() to limit usable memory ranges which are
described as entries in UEFI memory map table or "memory" nodes in
a device tree blob.

Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
Reviewed-by: Geoff Levand <geoff@infradead.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
---
 arch/arm64/mm/init.c | 35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

Comments

Mark Rutland Feb. 1, 2017, 3:07 p.m. UTC | #1 
Hi,

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

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

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

> +
> +	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,
	};

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,
Mark.

> +
> +	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
>
AKASHI Takahiro Feb. 2, 2017, 4:21 a.m. UTC | #2 
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:
> > +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

> > +	const __be32 *reg;
> > +	int len;
> > +
> > +	usablemem->size = 0;
> 
> Could we please lift this assignment/initialisation into the caller...
> 
> > +
> > +	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.
> 
> > +
> > +	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
> >
diff mbox

Patch

diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index 380ebe705093..6cddb566eb21 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -187,10 +187,45 @@  static int __init early_mem(char *p)
 }
 early_param("mem", early_mem);
 
+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;
+	const __be32 *reg;
+	int len;
+
+	usablemem->size = 0;
+
+	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;
+
+	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