linux-kernel - [PATCH] mips: kdump: Crash kernel should be able to see old memories

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Message-Id: <1618829807-12522-1-git-send-email-tangyouling@loongson.cn>
Date:   Mon, 19 Apr 2021 18:56:47 +0800
From:   Youling Tang <tangyouling@...ngson.cn>
To:     Thomas Bogendoerfer <tsbogend@...ha.franken.de>
Cc:     linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org,
        Huacai Chen <chenhuacai@...nel.org>
Subject: [PATCH] mips: kdump: Crash kernel should be able to see old memories

From: Huacai Chen <chenhc@...ote.com>

kexec-tools use mem=X@Y to pass usable memories to crash kernel, but in
commit a94e4f24ec836c8984f83959 ("MIPS: init: Drop boot_mem_map") all
BIOS passed memories are removed by early_parse_mem(). I think this is
reasonable for a normal kernel but not for a crash kernel, because a
crash kernel should be able to see all old memories, even though it is
not supposed to use them.

Fixes: a94e4f24ec836c8984f83959 ("MIPS: init: Drop boot_mem_map")
Signed-off-by: Huacai Chen <chenhuacai@...nel.org>
Signed-off-by: Youling Tang <tangyouling@...ngson.cn>
---
 arch/mips/kernel/setup.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/mips/kernel/setup.c b/arch/mips/kernel/setup.c
index b86e241..ac90d3b 100644
--- a/arch/mips/kernel/setup.c
+++ b/arch/mips/kernel/setup.c
@@ -351,8 +351,10 @@ static int __init early_parse_mem(char *p)
 	 */
 	if (usermem == 0) {
 		usermem = 1;
+#ifndef CONFIG_CRASH_DUMP
 		memblock_remove(memblock_start_of_DRAM(),
 			memblock_end_of_DRAM() - memblock_start_of_DRAM());
+#endif
 	}
 	start = 0;
 	size = memparse(p, &p);
-- 
2.1.0