arm64: kdump: Don't force page-level mappings for memory above 4G

hulk inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I545H8
CVE: NA

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

If the crashkernel reservation is deferred, such boundaries are not known
when the linear mapping is created. But its upper limit is fixed, cannot
above 4G. Therefore, unless otherwise required, block mapping should be
used for memory above 4G to improve performance.
Signed-off-by: NZhen Lei <thunder.leizhen@huawei.com>
Reviewed-by: NKefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

arch/arm64/mm/mmu.c

@@ -490,10 +490,10 @@ static void __init map_mem(pgd_t *pgdp)
 	phys_addr_t kernel_start = __pa_symbol(_text);
 	phys_addr_t kernel_end = __pa_symbol(__init_begin);
 	phys_addr_t start, end;
-	int flags = 0;
+	int flags = 0, eflags = 0;
 	u64 i;
 
-	if (rodata_full || crash_mem_map || debug_pagealloc_enabled())
+	if (rodata_full || debug_pagealloc_enabled())
 		flags = NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS;
 
 #ifdef CONFIG_KFENCE
@@ -514,17 +514,40 @@ static void __init map_mem(pgd_t *pgdp)
 	 */
 	memblock_mark_nomap(kernel_start, kernel_end - kernel_start);
 
+#ifdef CONFIG_KEXEC_CORE
+	if (crash_mem_map)
+		eflags = NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS;
+#endif
+
 	/* map all the memory banks */
 	for_each_mem_range(i, &start, &end) {
 		if (start >= end)
 			break;
+
+#ifdef CONFIG_KEXEC_CORE
+		if (eflags && (end >= SZ_4G)) {
+			/*
+			 * The memory block cross the 4G boundary.
+			 * Forcibly use page-level mappings for memory under 4G.
+			 */
+			if (start < SZ_4G) {
+				__map_memblock(pgdp, start, SZ_4G - 1,
+					       pgprot_tagged(PAGE_KERNEL), flags | eflags);
+				start  = SZ_4G;
+			}
+
+			/* Page-level mappings is not mandatory for memory above 4G */
+			eflags = 0;
+		}
+#endif
+
 		/*
 		 * The linear map must allow allocation tags reading/writing
 		 * if MTE is present. Otherwise, it has the same attributes as
 		 * PAGE_KERNEL.
 		 */
 		__map_memblock(pgdp, start, end, pgprot_tagged(PAGE_KERNEL),
-			       flags);
+			       flags | eflags);
 	}
 
 	/*