arm64/mm: Define defer_reserve_crashkernel()

Crash kernel memory reservation gets deferred, when either CONFIG_ZONE_DMA
or CONFIG_ZONE_DMA32 config is enabled on the platform. This deferral also
impacts overall linear mapping creation including the crash kernel itself.
Just encapsulate this deferral check in a new helper for better clarity.

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
Link: https://lore.kernel.org/r/20220705062556.1845734-1-anshuman.khandual@arm.comSigned-off-by: Will Deacon <will@kernel.org>

arch/arm64/include/asm/memory.h

@@ -351,6 +351,11 @@ static inline void *phys_to_virt(phys_addr_t x)
 })
 
 void dump_mem_limit(void);
+
+static inline bool defer_reserve_crashkernel(void)
+{
+	return IS_ENABLED(CONFIG_ZONE_DMA) || IS_ENABLED(CONFIG_ZONE_DMA32);
+}
 #endif /* !ASSEMBLY */
 
 /*

arch/arm64/mm/init.c

@@ -389,7 +389,7 @@ void __init arm64_memblock_init(void)
 
 	early_init_fdt_scan_reserved_mem();
 
-	if (!IS_ENABLED(CONFIG_ZONE_DMA) && !IS_ENABLED(CONFIG_ZONE_DMA32))
+	if (!defer_reserve_crashkernel())
 		reserve_crashkernel();
 
 	high_memory = __va(memblock_end_of_DRAM() - 1) + 1;
@@ -438,7 +438,7 @@ void __init bootmem_init(void)
 	 * request_standard_resources() depends on crashkernel's memory being
 	 * reserved, so do it here.
 	 */
-	if (IS_ENABLED(CONFIG_ZONE_DMA) || IS_ENABLED(CONFIG_ZONE_DMA32))
+	if (defer_reserve_crashkernel())
 		reserve_crashkernel();
 
 	memblock_dump_all();

arch/arm64/mm/mmu.c

@@ -529,8 +529,7 @@ static void __init map_mem(pgd_t *pgdp)
 
 #ifdef CONFIG_KEXEC_CORE
 	if (crash_mem_map) {
-		if (IS_ENABLED(CONFIG_ZONE_DMA) ||
-		    IS_ENABLED(CONFIG_ZONE_DMA32))
+		if (defer_reserve_crashkernel())
 			flags |= NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS;
 		else if (crashk_res.end)
 			memblock_mark_nomap(crashk_res.start,
@@ -571,8 +570,7 @@ static void __init map_mem(pgd_t *pgdp)
 	 * through /sys/kernel/kexec_crash_size interface.
 	 */
 #ifdef CONFIG_KEXEC_CORE
-	if (crash_mem_map &&
-	    !IS_ENABLED(CONFIG_ZONE_DMA) && !IS_ENABLED(CONFIG_ZONE_DMA32)) {
+	if (crash_mem_map && !defer_reserve_crashkernel()) {
 		if (crashk_res.end) {
 			__map_memblock(pgdp, crashk_res.start,
 				       crashk_res.end + 1,