Re: [PATCH] arm64/mm: Delete __init region from memblock.reserved

From: Rong Qianfeng
Date: Fri Aug 30 2024 - 04:25:46 EST



在 2024/8/30 16:14, Ard Biesheuvel 写道:
Hi Rong,

On Fri, 30 Aug 2024 at 10:00, Rong Qianfeng <rongqianfeng@xxxxxxxx> wrote:
If CONFIG_ARCH_KEEP_MEMBLOCK is enabled, the memory information in
memblock will be retained. We release the __init memory here, and
we should also delete the corresponding region in memblock.reserved.

Signed-off-by: Rong Qianfeng <rongqianfeng@xxxxxxxx>
---
arch/arm64/mm/init.c | 7 +++++++
1 file changed, 7 insertions(+)

diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index bfb10969cbf0..99cfa217e905 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -402,6 +402,13 @@ void __init mem_init(void)

void free_initmem(void)
{
+ if (IS_ENABLED(CONFIG_ARCH_KEEP_MEMBLOCK)) {
This is always true on arm64

+ unsigned long aligned_begin = ALIGN_DOWN((u64)__init_begin, PAGE_SIZE);
+ unsigned long aligned_end = ALIGN((u64)__init_end, PAGE_SIZE);
+
+ memblock_free((void *)aligned_begin, aligned_end - aligned_begin);
+ }
+
What does this achieve? The memory is already being reused by the page
allocator (due to free_reserved_area()), and the memblock allocator is
no longer usable at this point anyway.
If not,  incorrect information will be visible in
/sys/kernel/debug/memblock/reserved.

Best Regards,
Qianfeng

free_reserved_area(lm_alias(__init_begin),
lm_alias(__init_end),
POISON_FREE_INITMEM, "unused kernel");