Re: [PATCH v2] MIPS: replace add_memory_region with memblock

On Fri, Oct 09, 2020 at 02:07:52PM +0200, Thomas Bogendoerfer wrote:

On Thu, Oct 08, 2020 at 06:20:06PM +0300, Serge Semin wrote:

quoted

quoted

Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
---
Changes in v2:
	fixed missing memblock include in fw/sni/sniprom.c
	tested on cobalt, IP22, IP28, IP30, IP32, JAZZ, SNI

...

quoted

diff --git a/arch/mips/kernel/prom.c b/arch/mips/kernel/prom.c
index 9e50dc8df2f6..fab532cb5a11 100644
--- a/arch/mips/kernel/prom.c
+++ b/arch/mips/kernel/prom.c

@@ -50,14 +50,18 @@ void __init early_init_dt_add_memory_arch(u64 base, u64 size)
 		size = PHYS_ADDR_MAX - base;
 	}
 
-	add_memory_region(base, size, BOOT_MEM_RAM);
+	memblock_add(base, size);
 }
 
 int __init early_init_dt_reserve_memory_arch(phys_addr_t base,
 					phys_addr_t size, bool nomap)
 {
-	add_memory_region(base, size,
-			  nomap ? BOOT_MEM_NOMAP : BOOT_MEM_RESERVED);
+	if (nomap) {
+		memblock_remove(base, size);
+	} else {
+		memblock_add(base, size);
+		memblock_reserve(base, size);
+	}
 
 	return 0;
 }

I guess originally the arch-specific early_init_dt_add_memory_arch() and
early_init_dt_reserve_memory_arch() methods have been added since MIPS's got its
own memory types declarations (BOOT_MEM_RAM, BOOT_MEM_RESERVED, etc) and had had
a specific internal system memory regions mapping (add_memory_region(),
boot_mem_map, etc). Since the leftover of that framework is going to be removed,
we can freely use the standard early_init_dt_add_memory_arch() and
early_init_dt_reserve_memory_arch() implementations from drivers/of/fdt.c:1102
drivers/of/fdt.c:1149 .

perfect, I'll remove it in my next version.

quoted

quoted

@@ -426,13 +387,14 @@ static int __init early_parse_memmap(char *p)
 
 	if (*p == '@') {
 		start_at = memparse(p+1, &p);
-		add_memory_region(start_at, mem_size, BOOT_MEM_RAM);
+		memblock_add(start_at, mem_size);
 	} else if (*p == '#') {
 		pr_err("\"memmap=nn#ss\" (force ACPI data) invalid on MIPS\n");
 		return -EINVAL;
 	} else if (*p == '$') {
 		start_at = memparse(p+1, &p);

quoted

-		add_memory_region(start_at, mem_size, BOOT_MEM_RESERVED);
+		memblock_add(start_at, mem_size);
+		memblock_reserve(start_at, mem_size);

I suppose we could remove the memory addition from here too. What do you think?

I'm not sure about that, add_memory_region() did a memblock_add
and then memblock_reserve for BOOT_MEM_RESERVED, that's why I changed
it that way.

The main question here whether we need to preserve the MIPS-specific semantics
of the kernel 'memmap' parameter. Currently the memmap parameter passed with
'$' specifier will be perceived as a reserved RAM region, while, for instance, 
the same parameter on x86 will be converted to a region, which won't be
registered in memblock at all, so the system won't be able to reuse it if it's
needed to be (see parse_memmap_one() and e820__memblock_setup() for details).

I don't really know what approach is correct... 
Documentation/admin-guide/kernel-parameters.txt isn't certain about that. It
says that the region must be reserved, but no words whether it is supposed to be
mappable or non-mappable.

-Sergey

Thomas.

-- 
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea.                                                [ RFC1925, 2.3 ]

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