[PATCH v10 2/5] arm64: kdump: reserve crashkenel above 4G for crash dump kernel

[Chen Zhou]

Crashkernel=X tries to reserve memory for the crash dump kernel under
4G. If crashkernel=X,low is specified simultaneously, reserve spcified
size low memory for crash kdump kernel devices firstly and then reserve
memory above 4G.

Suggested by James, just introduced crashkernel=X,low to arm64. As memtioned
above, if crashkernel=X,low is specified simultaneously, reserve spcified
size low memory for crash kdump kernel devices firstly and then reserve
memory above 4G, which is much simpler.

Signed-off-by: Chen Zhou <chenzhou10@xxxxxxxxxx>
Tested-by: John Donnelly <John.p.donnelly@xxxxxxxxxx>
Tested-by: Prabhakar Kushwaha <pkushwaha@xxxxxxxxxxx>
---
 arch/arm64/kernel/setup.c |  8 +++++++-
 arch/arm64/mm/init.c      | 31 +++++++++++++++++++++++++++++--
 2 files changed, 36 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
index 93b3844cf442..4dc51a2ac012 100644
--- a/arch/arm64/kernel/setup.c
+++ b/arch/arm64/kernel/setup.c
@@ -238,7 +238,13 @@ static void __init request_standard_resources(void)
 		    kernel_data.end <= res->end)
 			request_resource(res, &kernel_data);
 #ifdef CONFIG_KEXEC_CORE
-		/* Userspace will find "Crash kernel" region in /proc/iomem. */
+		/*
+		 * Userspace will find "Crash kernel" region in /proc/iomem.
+		 * Note: the low region is renamed as Crash kernel (low).
+		 */
+		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 1e93cfc7c47a..ce7ced85f5fb 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -81,6 +81,7 @@ static void __init reserve_crashkernel(void)
 {
 	unsigned long long crash_base, crash_size;
 	int ret;
+	phys_addr_t crash_max = arm64_dma32_phys_limit;
 
 	ret = parse_crashkernel(boot_command_line, memblock_phys_mem_size(),
 				&crash_size, &crash_base);
@@ -88,12 +89,38 @@ static void __init reserve_crashkernel(void)
 	if (ret || !crash_size)
 		return;
 
+	ret = reserve_crashkernel_low();
+	if (!ret && crashk_low_res.end) {
+		/*
+		 * If crashkernel=X,low specified, there may be two regions,
+		 * we need to make some changes as follows:
+		 *
+		 * 1. rename the low region as "Crash kernel (low)"
+		 * In order to distinct from the high region and make no effect
+		 * to the use of existing kexec-tools, rename the low region as
+		 * "Crash kernel (low)".
+		 *
+		 * 2. change the upper bound for crash memory
+		 * Set MEMBLOCK_ALLOC_ACCESSIBLE upper bound for crash memory.
+		 *
+		 * 3. mark the low region as "nomap"
+		 * The low region is intended to be used for crash dump kernel
+		 * devices, just mark the low region as "nomap" simply.
+		 */
+		const char *rename = "Crash kernel (low)";
+
+		crashk_low_res.name = rename;
+		crash_max = MEMBLOCK_ALLOC_ACCESSIBLE;
+		memblock_mark_nomap(crashk_low_res.start,
+				    resource_size(&crashk_low_res));
+	}
+
 	crash_size = PAGE_ALIGN(crash_size);
 
 	if (crash_base == 0) {
 		/* Current arm64 boot protocol requires 2MB alignment */
-		crash_base = memblock_find_in_range(0, arm64_dma32_phys_limit,
-				crash_size, SZ_2M);
+		crash_base = memblock_find_in_range(0, crash_max, crash_size,
+				SZ_2M);
 		if (crash_base == 0) {
 			pr_warn("cannot allocate crashkernel (size:0x%llx)\n",
 				crash_size);
-- 
2.20.1