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SubjectRe: [PATCH v15 09/10] of: fdt: Add memory for devices by DT property "linux,usable-memory-range"
On Wed, Oct 20, 2021 at 10:03:16AM +0800, Zhen Lei wrote:
> From: Chen Zhou <chenzhou10@huawei.com>
>
> When reserving crashkernel in high memory, some low memory is reserved
> for crash dump kernel devices and never mapped by the first kernel.
> This memory range is advertised to crash dump kernel via DT property
> under /chosen,
> linux,usable-memory-range = <BASE1 SIZE1 [BASE2 SIZE2]>
>
> We reused the DT property linux,usable-memory-range and made the low
> memory region as the second range "BASE2 SIZE2", which keeps compatibility
> with existing user-space and older kdump kernels.
>
> Crash dump kernel reads this property at boot time and call memblock_add()
> to add the low memory region after memblock_cap_memory_range() has been
> called.
>
> Signed-off-by: Chen Zhou <chenzhou10@huawei.com>
> Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
> ---
> drivers/of/fdt.c | 47 ++++++++++++++++++++++++++++++++++++-----------
> 1 file changed, 36 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
> index 4546572af24bbf1..cf59c847b2c28a5 100644
> --- a/drivers/of/fdt.c
> +++ b/drivers/of/fdt.c
> @@ -969,8 +969,16 @@ static void __init early_init_dt_check_for_elfcorehdr(unsigned long node)
> elfcorehdr_addr, elfcorehdr_size);
> }
>
> -static phys_addr_t cap_mem_addr;
> -static phys_addr_t cap_mem_size;
> +/*
> + * The main usage of linux,usable-memory-range is for crash dump kernel.
> + * Originally, the number of usable-memory regions is one. Now there may
> + * be two regions, low region and high region.
> + * To make compatibility with existing user-space and older kdump, the low
> + * region is always the last range of linux,usable-memory-range if exist.
> + */
> +#define MAX_USABLE_RANGES 2
> +
> +static struct memblock_region cap_mem_regions[MAX_USABLE_RANGES];
>
> /**
> * early_init_dt_check_for_usable_mem_range - Decode usable memory range
> @@ -979,20 +987,30 @@ static phys_addr_t cap_mem_size;
> */
> static void __init early_init_dt_check_for_usable_mem_range(unsigned long node)
> {
> - const __be32 *prop;
> - int len;
> + const __be32 *prop, *endp;
> + int len, nr = 0;
> + struct memblock_region *rgn = &cap_mem_regions[0];
>
> pr_debug("Looking for usable-memory-range property... ");
>
> prop = of_get_flat_dt_prop(node, "linux,usable-memory-range", &len);
> - if (!prop || (len < (dt_root_addr_cells + dt_root_size_cells)))
> + if (!prop)
> return;
>
> - cap_mem_addr = dt_mem_next_cell(dt_root_addr_cells, &prop);
> - cap_mem_size = dt_mem_next_cell(dt_root_size_cells, &prop);
> + endp = prop + (len / sizeof(__be32));
> + while ((endp - prop) >= (dt_root_addr_cells + dt_root_size_cells)) {
> + rgn->base = dt_mem_next_cell(dt_root_addr_cells, &prop);
> + rgn->size = dt_mem_next_cell(dt_root_size_cells, &prop);
> +
> + pr_debug("cap_mem_regions[%d]: base=%pa, size=%pa\n",
> + nr, &rgn->base, &rgn->size);
> +
> + if (++nr >= MAX_USABLE_RANGES)
> + break;
> +
> + rgn++;
> + }
>
> - pr_debug("cap_mem_start=%pa cap_mem_size=%pa\n", &cap_mem_addr,
> - &cap_mem_size);
> }
>
> #ifdef CONFIG_SERIAL_EARLYCON
> @@ -1265,7 +1283,8 @@ bool __init early_init_dt_verify(void *params)
>
> void __init early_init_dt_scan_nodes(void)
> {
> - int rc = 0;
> + int i, rc = 0;
> + struct memblock_region *rgn = &cap_mem_regions[0];
>
> /* Initialize {size,address}-cells info */
> of_scan_flat_dt(early_init_dt_scan_root, NULL);
> @@ -1279,7 +1298,13 @@ void __init early_init_dt_scan_nodes(void)
> of_scan_flat_dt(early_init_dt_scan_memory, NULL);
>
> /* Handle linux,usable-memory-range property */
> - memblock_cap_memory_range(cap_mem_addr, cap_mem_size);
> + memblock_cap_memory_range(rgn->base, rgn->size);
> + for (i = 1; i < MAX_USABLE_RANGES; i++) {
> + rgn++;

Just use rgn[i].

> +
> + if (rgn->size)

This check can be in the 'for' conditions check.

> + memblock_add(rgn->base, rgn->size);
> + }


There's not really any point in doing all this in 2 steps. I'm
assuming this needs to be handled after scanning the memory nodes, so
can you refactor this moving early_init_dt_check_for_usable_mem_range
out of early_init_dt_scan_chosen() and call it here. You'll have to get
the offset for /chosen twice or save the offset.

Rob

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