[PATCH v2 2/3] arm64: mm: Don't defer reserve_crashkernel() with dma_force_32bit

[Kefeng Wang]

ARM64 enable ZONE_DMA by default, and with ZONE_DMA crash kernel
memory reservation is delayed until DMA zone memory range size
initilazation performed in zone_sizes_init(), but for most platforms
use 32bit dma_zone_bits, so add dma_force_32bit kernel parameter
if ZONE_DMA enabled, and initialize arm64_dma_phys_limit to
dma32_phys_limit in arm64_memblock_init() if dma_force_32bit
is setup, this could let the crash kernel reservation earlier,
and allows linear creation with block mapping.

Signed-off-by: Kefeng Wang <wangkefeng.wang at huawei.com>
---
 arch/arm64/include/asm/kexec.h |  1 +
 arch/arm64/mm/init.c           | 42 ++++++++++++++++++++++++++--------
 arch/arm64/mm/mmu.c            |  4 ++--
 3 files changed, 36 insertions(+), 11 deletions(-)

diff --git a/arch/arm64/include/asm/kexec.h b/arch/arm64/include/asm/kexec.h
index 9839bfc163d7..653b16acd09a 100644
--- a/arch/arm64/include/asm/kexec.h
+++ b/arch/arm64/include/asm/kexec.h
@@ -94,6 +94,7 @@ static inline void crash_post_resume(void) {}
 void cpu_soft_restart(unsigned long el2_switch, unsigned long entry,
 		      unsigned long arg0, unsigned long arg1,
 		      unsigned long arg2);
+bool crashkernel_could_early_reserve(void)
 #endif
 
 #define ARCH_HAS_KIMAGE_ARCH
diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index fb01eb489fa9..329e236c3c52 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -66,7 +66,8 @@ EXPORT_SYMBOL(memstart_addr);
  * depending on DMA memory zones configs (ZONE_DMA) --
  *
  * In absence of ZONE_DMA and ZONE_DMA32 configs arm64_dma_phys_limit
- * initialized here and if only with ZONE_DMA32 arm64_dma_phys_limit
+ * initialized here, and if only with ZONE_DMA32 or if with ZONE_DMA
+ * and dma_force_32bit kernel parameter, the arm64_dma_phys_limit is
  * initialised to dma32_phys_limit. This lets early reservation of
  * crash kernel memory which has a dependency on arm64_dma_phys_limit.
  * Reserving memory early for crash kernel allows linear creation of block
@@ -92,6 +93,27 @@ phys_addr_t __ro_after_init arm64_dma_phys_limit;
 phys_addr_t __ro_after_init arm64_dma_phys_limit = PHYS_MASK + 1;
 #endif
 
+static bool __ro_after_init arm64_dma_force_32bit;
+#ifdef CONFIG_ZONE_DMA
+static int __init arm64_dma_force_32bit_setup(char *p)
+{
+	zone_dma_bits = 32;
+	arm64_dma_force_32bit = true;
+
+	return 0;
+}
+early_param("dma_force_32bit", arm64_dma_force_32bit_setup);
+#endif
+
+bool __init crashkernel_could_early_reserve(void)
+{
+	if (!IS_ENABLED(CONFIG_ZONE_DMA))
+		return true;
+	if (arm64_dma_force_32bit)
+		return true;
+	return false;
+}
+
 /*
  * reserve_crashkernel() - reserves memory for crash kernel
  *
@@ -163,12 +185,14 @@ static void __init zone_sizes_init(unsigned long min, unsigned long max)
 {
 	unsigned long max_zone_pfns[MAX_NR_ZONES]  = {0};
 #ifdef CONFIG_ZONE_DMA
-	unsigned int acpi_zone_dma_bits;
-	unsigned int dt_zone_dma_bits;
+	if (!arm64_dma_force_32bit) {
+		unsigned int acpi_zone_dma_bits;
+		unsigned int dt_zone_dma_bits;
 
-	acpi_zone_dma_bits = fls64(acpi_iort_dma_get_max_cpu_address());
-	dt_zone_dma_bits = fls64(of_dma_get_max_cpu_address(NULL));
-	zone_dma_bits = min3(32U, dt_zone_dma_bits, acpi_zone_dma_bits);
+		acpi_zone_dma_bits = fls64(acpi_iort_dma_get_max_cpu_address());
+		dt_zone_dma_bits = fls64(of_dma_get_max_cpu_address(NULL));
+		zone_dma_bits = min3(32U, dt_zone_dma_bits, acpi_zone_dma_bits);
+	}
 	arm64_dma_phys_limit = max_zone_phys(zone_dma_bits);
 	max_zone_pfns[ZONE_DMA] = PFN_DOWN(arm64_dma_phys_limit);
 #endif
@@ -336,8 +360,8 @@ void __init arm64_memblock_init(void)
 	early_init_fdt_scan_reserved_mem();
 
 	dma32_phys_limit = max_zone_phys(32);
-	if (!IS_ENABLED(CONFIG_ZONE_DMA)) {
-		if (IS_ENABLED(CONFIG_ZONE_DMA32))
+	if (crashkernel_could_early_reserve()) {
+		if (IS_ENABLED(CONFIG_ZONE_DMA32) || dma_force_32bit)
 			arm64_dma_phys_limit = dma32_phys_limit;
 		reserve_crashkernel();
 	}
@@ -388,7 +412,7 @@ 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))
+	if (!crashkernel_could_early_reserve())
 		reserve_crashkernel();
 
 	memblock_dump_all();
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 23734481318a..8f7e8452d906 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -529,7 +529,7 @@ static void __init map_mem(pgd_t *pgdp)
 
 #ifdef CONFIG_KEXEC_CORE
 	if (crash_mem_map) {
-		if (IS_ENABLED(CONFIG_ZONE_DMA))
+		if (!crashkernel_could_early_reserve())
 			flags |= NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS;
 		else if (crashk_res.end)
 			memblock_mark_nomap(crashk_res.start,
@@ -570,7 +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)) {
+	if (crash_mem_map && crashkernel_could_early_reserve()) {
 		if (crashk_res.end) {
 			__map_memblock(pgdp, crashk_res.start,
 				       crashk_res.end + 1,
-- 
2.26.2