Re: [PATCH v5 1/9] MIPS: Avoid future duplicate elf core header reservation

Hi Mike,

On Mon, Aug 16, 2021 at 7:52 AM Mike Rapoport [off-list ref] wrote:

On Wed, Aug 11, 2021 at 10:50:59AM +0200, Geert Uytterhoeven wrote:

quoted

Prepare for early_init_fdt_scan_reserved_mem() reserving the memory
occupied by an elf core header described in the device tree.
As arch_mem_init() calls early_init_fdt_scan_reserved_mem() before
mips_reserve_vmcore(), the latter needs to check if the memory has
already been reserved before.

Doing memblock_reserve() for the same region is usually fine, did you
encounter any issues without this patch?

Does it also work if the same region is part of an earlier larger
reservation?  I am no memblock expert, so I don't know.
I didn't run into any issues, as my MIPS platform is non-DT, but I
assume arch/arm64/mm/init.c:reserve_elfcorehdr() had the check for
a reason.

Thanks!

quoted

Note that mips_reserve_vmcore() cannot just be removed, as not all MIPS
systems use DT.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
---
v5:
  - New.
---
 arch/mips/kernel/setup.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/mips/kernel/setup.c b/arch/mips/kernel/setup.c
index 23a140327a0bac1b..4693add05743d78b 100644
--- a/arch/mips/kernel/setup.c
+++ b/arch/mips/kernel/setup.c

@@ -429,7 +429,8 @@ static void __init mips_reserve_vmcore(void)
      pr_info("Reserving %ldKB of memory at %ldKB for kdump\n",
              (unsigned long)elfcorehdr_size >> 10, (unsigned long)elfcorehdr_addr >> 10);

-     memblock_reserve(elfcorehdr_addr, elfcorehdr_size);
+     if (!memblock_is_region_reserved(elfcorehdr_addr, elfcorehdr_size)
+             memblock_reserve(elfcorehdr_addr, elfcorehdr_size);
 #endif
 }

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

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