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diff --git a/arch/x86/include/asm/crash_reserve.h b/arch/x86/include/asm/crash_reserve.h
new file mode 100644
index 000000000000..152239f95541
--- /dev/null
+++ b/arch/x86/include/asm/crash_reserve.h
@@ -0,0 +1,42 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _X86_CRASH_RESERVE_H
+#define _X86_CRASH_RESERVE_H
+
+/* 16M alignment for crash kernel regions */
+#define CRASH_ALIGN             SZ_16M
+
+/*
+ * Keep the crash kernel below this limit.
+ *
+ * Earlier 32-bits kernels would limit the kernel to the low 512 MB range
+ * due to mapping restrictions.
+ *
+ * 64-bit kdump kernels need to be restricted to be under 64 TB, which is
+ * the upper limit of system RAM in 4-level paging mode. Since the kdump
+ * jump could be from 5-level paging to 4-level paging, the jump will fail if
+ * the kernel is put above 64 TB, and during the 1st kernel bootup there's
+ * no good way to detect the paging mode of the target kernel which will be
+ * loaded for dumping.
+ */
+extern unsigned long swiotlb_size_or_default(void);
+
+#ifdef CONFIG_X86_32
+# define CRASH_ADDR_LOW_MAX     SZ_512M
+# define CRASH_ADDR_HIGH_MAX    SZ_512M
+#else
+# define CRASH_ADDR_LOW_MAX     SZ_4G
+# define CRASH_ADDR_HIGH_MAX    SZ_64T
+#endif
+
+# define DEFAULT_CRASH_KERNEL_LOW_SIZE crash_low_size_default()
+
+static inline unsigned long crash_low_size_default(void)
+{
+#ifdef CONFIG_X86_64
+	return max(swiotlb_size_or_default() + (8UL << 20), 256UL << 20);
+#else
+	return 0;
+#endif
+}
+
+#endif /* _X86_CRASH_RESERVE_H */