[PATCH v3 2/4] arm64: kdump: support reserving crashkernel above 4G

[Chen Zhou]

When crashkernel is reserved above 4G in memory, kernel should
reserve some amount of low memory for swiotlb and some DMA buffers.

Kernel would try to allocate at least 256M below 4G automatically
as x86_64 if crashkernel is above 4G. Meanwhile, support
crashkernel=X,[high,low] in arm64.

Signed-off-by: Chen Zhou <chenzhou10@xxxxxxxxxx>
---
 arch/arm64/include/asm/kexec.h |  3 +++
 arch/arm64/kernel/setup.c      |  3 +++
 arch/arm64/mm/init.c           | 26 +++++++++++++++++++++-----
 3 files changed, 27 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/include/asm/kexec.h b/arch/arm64/include/asm/kexec.h
index 67e4cb7..32949bf 100644
--- a/arch/arm64/include/asm/kexec.h
+++ b/arch/arm64/include/asm/kexec.h
@@ -28,6 +28,9 @@
 
 #define KEXEC_ARCH KEXEC_ARCH_AARCH64
 
+/* 2M alignment for crash kernel regions */
+#define CRASH_ALIGN	SZ_2M
+
 #ifndef __ASSEMBLY__
 
 /**
diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
index 413d566..82cd9a0 100644
--- a/arch/arm64/kernel/setup.c
+++ b/arch/arm64/kernel/setup.c
@@ -243,6 +243,9 @@ static void __init request_standard_resources(void)
 			request_resource(res, &kernel_data);
 #ifdef CONFIG_KEXEC_CORE
 		/* Userspace will find "Crash kernel" region in /proc/iomem. */
+		if (crashk_low_res.end && crashk_low_res.start >= res->start &&
+		    crashk_low_res.end <= res->end)
+			request_resource(res, &crashk_low_res);
 		if (crashk_res.end && crashk_res.start >= res->start &&
 		    crashk_res.end <= res->end)
 			request_resource(res, &crashk_res);
diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index 972bf43..3bebddf 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -64,6 +64,7 @@ EXPORT_SYMBOL(memstart_addr);
 phys_addr_t arm64_dma_phys_limit __ro_after_init;
 
 #ifdef CONFIG_KEXEC_CORE
+
 /*
  * reserve_crashkernel() - reserves memory for crash kernel
  *
@@ -74,20 +75,30 @@ phys_addr_t arm64_dma_phys_limit __ro_after_init;
 static void __init reserve_crashkernel(void)
 {
 	unsigned long long crash_base, crash_size;
+	bool high = false;
 	int ret;
 
 	ret = parse_crashkernel(boot_command_line, memblock_phys_mem_size(),
 				&crash_size, &crash_base);
 	/* no crashkernel= or invalid value specified */
-	if (ret || !crash_size)
-		return;
+	if (ret || !crash_size) {
+		/* crashkernel=X,high */
+		ret = parse_crashkernel_high(boot_command_line,
+				memblock_phys_mem_size(),
+				&crash_size, &crash_base);
+		if (ret || !crash_size)
+			return;
+		high = true;
+	}
 
 	crash_size = PAGE_ALIGN(crash_size);
 
 	if (crash_base == 0) {
 		/* Current arm64 boot protocol requires 2MB alignment */
-		crash_base = memblock_find_in_range(0, ARCH_LOW_ADDRESS_LIMIT,
-				crash_size, SZ_2M);
+		crash_base = memblock_find_in_range(0,
+				high ? memblock_end_of_DRAM()
+				: ARCH_LOW_ADDRESS_LIMIT,
+				crash_size, CRASH_ALIGN);
 		if (crash_base == 0) {
 			pr_warn("cannot allocate crashkernel (size:0x%llx)\n",
 				crash_size);
@@ -105,13 +116,18 @@ static void __init reserve_crashkernel(void)
 			return;
 		}
 
-		if (!IS_ALIGNED(crash_base, SZ_2M)) {
+		if (!IS_ALIGNED(crash_base, CRASH_ALIGN)) {
 			pr_warn("cannot reserve crashkernel: base address is not 2MB aligned\n");
 			return;
 		}
 	}
 	memblock_reserve(crash_base, crash_size);
 
+	if (crash_base >= SZ_4G && reserve_crashkernel_low()) {
+		memblock_free(crash_base, crash_size);
+		return;
+	}
+
 	pr_info("crashkernel reserved: 0x%016llx - 0x%016llx (%lld MB)\n",
 		crash_base, crash_base + crash_size, crash_size >> 20);
 
-- 
2.7.4