Re: [PATCH v24 4/6] of: fdt: Add memory for devices by DT property "linux,usable-memory-range"

Baoquan He
2022-05-06T23:16:17Z

On 05/06/22 at 07:44pm, 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.

LGTM,

Acked-by: Baoquan He <bhe@redhat.com>

>
> Signed-off-by: Chen Zhou <chenzhou10@huawei.com>
> Co-developed-by: Zhen Lei <thunder.leizhen@huawei.com>
> Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
> Reviewed-by: Rob Herring <robh@kernel.org>
> Tested-by: Dave Kleikamp <dave.kleikamp@oracle.com>
> ---
> drivers/of/fdt.c | 33 +++++++++++++++++++++++----------
> 1 file changed, 23 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
> index ec315b060cd50d2..2f248d0acc04830 100644
> --- a/drivers/of/fdt.c
> +++ b/drivers/of/fdt.c
> @@ -973,16 +973,24 @@ static void __init early_init_dt_check_for_elfcorehdr(unsigned long node)
>
> static unsigned long chosen_node_offset = -FDT_ERR_NOTFOUND;
>
> +/*
> + * 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
> +
> /**
> * early_init_dt_check_for_usable_mem_range - Decode usable memory range
> * location from flat tree
> */
> void __init early_init_dt_check_for_usable_mem_range(void)
> {
> - const __be32 *prop;
> - int len;
> - phys_addr_t cap_mem_addr;
> - phys_addr_t cap_mem_size;
> + struct memblock_region rgn[MAX_USABLE_RANGES] = {0};
> + const __be32 *prop, *endp;
> + int len, i;
> unsigned long node = chosen_node_offset;
>
> if ((long)node < 0)
> @@ -991,16 +999,21 @@ void __init early_init_dt_check_for_usable_mem_range(void)
> 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 || (len % (dt_root_addr_cells + dt_root_size_cells)))
> 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));
> + for (i = 0; i < MAX_USABLE_RANGES && prop < endp; i++) {
> + rgn[i].base = dt_mem_next_cell(dt_root_addr_cells, &prop);
> + rgn[i].size = dt_mem_next_cell(dt_root_size_cells, &prop);
>
> - pr_debug("cap_mem_start=%pa cap_mem_size=%pa\n", &cap_mem_addr,
> - &cap_mem_size);
> + pr_debug("cap_mem_regions[%d]: base=%pa, size=%pa\n",
> + i, &rgn[i].base, &rgn[i].size);
> + }
>
> - memblock_cap_memory_range(cap_mem_addr, cap_mem_size);
> + memblock_cap_memory_range(rgn[0].base, rgn[0].size);
> + for (i = 1; i < MAX_USABLE_RANGES && rgn[i].size; i++)
> + memblock_add(rgn[i].base, rgn[i].size);
> }
>
> #ifdef CONFIG_SERIAL_EARLYCON
> --
> 2.25.1
>