[PATCH v2 2/2] LoongArch: kdump: Add crashkernel=YM handling

[Youling Tang]

When the kernel crashkernel parameter is specified with just a size,
we are supposed to allocate a region from RAM to store the crashkernel,
"crashkernel=512M" would be recommended for kdump.

Fix this by lifting similar code from x86, importing it to LoongArch
with the LoongArch specific parameters added. We allocate the crashkernel
region from the first 4G of physical memory (SWIOTLB needs to be allocated
on low 4G). Currently LoongArch does not implement crashkernel_low and
crashkernel_high like x86.

When X is not specified, crash_base defaults to 0 (crashkernel=YM@XM).

Signed-off-by: Youling Tang <tangyouling@xxxxxxxxxxx>
---
 arch/loongarch/kernel/setup.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/arch/loongarch/kernel/setup.c b/arch/loongarch/kernel/setup.c
index 4344502c0b31..ac2aad988fdb 100644
--- a/arch/loongarch/kernel/setup.c
+++ b/arch/loongarch/kernel/setup.c
@@ -234,11 +234,14 @@ static void __init arch_reserve_vmcore(void)
 #endif
 }
 
+/* 16M alignment for crash kernel regions */
+#define CRASH_ALIGN	SZ_16M
+#define CRASH_ADDR_MAX	SZ_4G
+
 static void __init arch_parse_crashkernel(void)
 {
 #ifdef CONFIG_KEXEC
 	int ret;
-	unsigned long long start;
 	unsigned long long total_mem;
 	unsigned long long crash_base, crash_size;
 
@@ -247,8 +250,14 @@ static void __init arch_parse_crashkernel(void)
 	if (ret < 0 || crash_size <= 0)
 		return;
 
-	start = memblock_phys_alloc_range(crash_size, 1, crash_base, crash_base + crash_size);
-	if (start != crash_base) {
+	if (crash_base <= 0) {
+		crash_base = memblock_phys_alloc_range(crash_size, CRASH_ALIGN, CRASH_ALIGN,
+				CRASH_ADDR_MAX);
+		if (!crash_base) {
+			pr_warn("crashkernel reservation failed - No suitable area found.\n");
+			return;
+		}
+	} else if (!memblock_phys_alloc_range(crash_size, 1, crash_base, crash_base + crash_size)) {
 		pr_warn("Invalid memory region reserved for crash kernel\n");
 		return;
 	}
-- 
2.37.3