On Fri, 13 Mar 2020 12:06:37 +0900, <kjhg4321@naver.com> said:
In the __reserved_mem_reserve_reg() function, I found something that I couldn't easily understand.
To get help, I sent an e-mail to this mailing list.
if (first) { fdt_reserved_mem_save_node(node, uname, base, size); first = 0; }
I found that fdt_reserved_mem_save_node() is called the regardless of memblock remove/reserve success.
I think early_init_dt_reserve_memory_arch() can fail.(ex. for the lack of memblock's region)
So I wonder there will be a situation where reserved_mem initialization will be executed without memory reservation.
What you probably missed is that function is wrapped in a #ifdef CONFIG_OF_EARLY_FLATTREE - and is called to read in the OF devicetree data and save it in a form the kernel can use.
So there usually shouldn't be a problem in reserving memory early in boot, unless of course somebody bollixed up a devicetree entry and put in bad values for base, size, and nomap.
But, This is when the early memory allocation is not active. Therefore, if memblock's region[128] is full, memblock_reserve/remove() can fail.(Of course, there should be more than 128 reserved memory.)
However, fdt_reserved_mem_save_node() needs to happen anyhow, because that's not initialiing the memory that wasn't actually reserved, it's recording the fact that the devicetree had a reserved memory request in it, and that needs to be remembered because there's a second pass over the devicetree data later on (or so the comments in drivers/of/of_reserved_mem.c tell me).
Yes, fdt_reserved_mem_save_node() just register the reseved memory in the reserve_mem. then, reserved_mem is passed to _reserved_mem_init_node(). But In this function, If the node is "cma", it will call rmem_cma_setup() and it will initializing the cma struct, So what I was wondering was wouldn't the cma structure be initialized without memory being reserved? _______________________________________________ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies