[PATCH 2/3] arm64: kdump: support more than one crash kernel regions

[Chen Zhou <chenzhou10@xxxxxxxxxx>]

After commit (arm64: kdump: support reserving crashkernel above 4G),
there may be two crash kernel regions, one is below 4G, the other is
above 4G.

Crash dump kernel reads more than one crash kernel regions via a dtb
property under node /chosen,
linux,usable-memory-range = <BASE1 SIZE1 [BASE2 SIZE2]>

Signed-off-by: Chen Zhou <chenzhou10@xxxxxxxxxx>
---
 arch/arm64/mm/init.c     | 37 +++++++++++++++++++++++++------------
 include/linux/memblock.h |  1 +
 mm/memblock.c            | 40 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 66 insertions(+), 12 deletions(-)

diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index ceb2a25..769c77a 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -64,6 +64,8 @@ EXPORT_SYMBOL(memstart_addr);
 phys_addr_t arm64_dma_phys_limit __ro_after_init;
 
 #ifdef CONFIG_KEXEC_CORE
+# define CRASH_MAX_USABLE_RANGES        2
+
 static int __init reserve_crashkernel_low(void)
 {
 	unsigned long long base, low_base = 0, low_size = 0;
@@ -346,8 +348,8 @@ static int __init early_init_dt_scan_usablemem(unsigned long node,
 		const char *uname, int depth, void *data)
 {
 	struct memblock_region *usablemem = data;
-	const __be32 *reg;
-	int len;
+	const __be32 *reg, *endp;
+	int len, nr = 0;
 
 	if (depth != 1 || strcmp(uname, "chosen") != 0)
 		return 0;
@@ -356,22 +358,33 @@ static int __init early_init_dt_scan_usablemem(unsigned long node,
 	if (!reg || (len < (dt_root_addr_cells + dt_root_size_cells)))
 		return 1;
 
-	usablemem->base = dt_mem_next_cell(dt_root_addr_cells, &reg);
-	usablemem->size = dt_mem_next_cell(dt_root_size_cells, &reg);
+	endp = reg + (len / sizeof(__be32));
+	while ((endp - reg) >= (dt_root_addr_cells + dt_root_size_cells)) {
+		usablemem[nr].base = dt_mem_next_cell(dt_root_addr_cells, &reg);
+		usablemem[nr].size = dt_mem_next_cell(dt_root_size_cells, &reg);
+
+		if (++nr >= CRASH_MAX_USABLE_RANGES)
+			break;
+	}
 
 	return 1;
 }
 
 static void __init fdt_enforce_memory_region(void)
 {
-	struct memblock_region reg = {
-		.size = 0,
-	};
-
-	of_scan_flat_dt(early_init_dt_scan_usablemem, &reg);
-
-	if (reg.size)
-		memblock_cap_memory_range(reg.base, reg.size);
+	int i, cnt = 0;
+	struct memblock_region regs[CRASH_MAX_USABLE_RANGES];
+
+	memset(regs, 0, sizeof(regs));
+	of_scan_flat_dt(early_init_dt_scan_usablemem, regs);
+
+	for (i = 0; i < CRASH_MAX_USABLE_RANGES; i++)
+		if (regs[i].size)
+			cnt++;
+		else
+			break;
+	if (cnt)
+		memblock_cap_memory_ranges(regs, cnt);
 }
 
 void __init arm64_memblock_init(void)
diff --git a/include/linux/memblock.h b/include/linux/memblock.h
index 47e3c06..aeade34 100644
--- a/include/linux/memblock.h
+++ b/include/linux/memblock.h
@@ -446,6 +446,7 @@ phys_addr_t memblock_start_of_DRAM(void);
 phys_addr_t memblock_end_of_DRAM(void);
 void memblock_enforce_memory_limit(phys_addr_t memory_limit);
 void memblock_cap_memory_range(phys_addr_t base, phys_addr_t size);
+void memblock_cap_memory_ranges(struct memblock_region *regs, int cnt);
 void memblock_mem_limit_remove_map(phys_addr_t limit);
 bool memblock_is_memory(phys_addr_t addr);
 bool memblock_is_map_memory(phys_addr_t addr);
diff --git a/mm/memblock.c b/mm/memblock.c
index 28fa8926..1a7f4ee7c 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -1697,6 +1697,46 @@ void __init memblock_cap_memory_range(phys_addr_t base, phys_addr_t size)
 			base + size, PHYS_ADDR_MAX);
 }
 
+void __init memblock_cap_memory_ranges(struct memblock_region *regs, int cnt)
+{
+	int start_rgn[INIT_MEMBLOCK_REGIONS], end_rgn[INIT_MEMBLOCK_REGIONS];
+	int i, j, ret, nr = 0;
+
+	for (i = 0; i < cnt; i++) {
+		ret = memblock_isolate_range(&memblock.memory, regs[i].base,
+				regs[i].size, &start_rgn[i], &end_rgn[i]);
+		if (ret)
+			break;
+		nr++;
+	}
+	if (!nr)
+		return;
+
+	/* remove all the MAP regions */
+	for (i = memblock.memory.cnt - 1; i >= end_rgn[nr - 1]; i--)
+		if (!memblock_is_nomap(&memblock.memory.regions[i]))
+			memblock_remove_region(&memblock.memory, i);
+
+	for (i = nr - 1; i > 0; i--)
+		for (j = start_rgn[i] - 1; j >= end_rgn[i - 1]; j--)
+			if (!memblock_is_nomap(&memblock.memory.regions[j]))
+				memblock_remove_region(&memblock.memory, j);
+
+	for (i = start_rgn[0] - 1; i >= 0; i--)
+		if (!memblock_is_nomap(&memblock.memory.regions[i]))
+			memblock_remove_region(&memblock.memory, i);
+
+	/* truncate the reserved regions */
+	memblock_remove_range(&memblock.reserved, 0, regs[0].base);
+
+	for (i = nr - 1; i > 0; i--)
+		memblock_remove_range(&memblock.reserved,
+				regs[i].base, regs[i - 1].base + regs[i - 1].size);
+
+	memblock_remove_range(&memblock.reserved,
+			regs[nr - 1].base + regs[nr - 1].size, PHYS_ADDR_MAX);
+}
+
 void __init memblock_mem_limit_remove_map(phys_addr_t limit)
 {
 	phys_addr_t max_addr;
-- 
2.7.4