arm64: kdump: support reserving crashkernel above 4G

hulk inclusion
category: feature
bugzilla: 12800
CVE: NA

-------------------------------------------------

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: NChen Zhou <chenzhou10@huawei.com>
Reviewed-by: NYang Yingliang <yangyingliang@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

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__
 
 /**

arch/arm64/kernel/setup.c

@@ -253,6 +253,9 @@ 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);

arch/arm64/mm/init.c

@@ -94,20 +94,30 @@ early_param("initrd", early_initrd);
 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);
@@ -125,13 +135,18 @@ 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);