linux-kernel - [PATCH v2 1/3] arm64: mm: Do not defer reserve_crashkernel() if only ZONE

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Date:   Thu, 31 Mar 2022 10:59:44 +0800
From:   Kefeng Wang <wangkefeng.wang@...wei.com>
To:     <catalin.marinas@....com>, <will@...nel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
CC:     <vijayb@...ux.microsoft.com>, <f.fainelli@...il.com>,
        Kefeng Wang <wangkefeng.wang@...wei.com>,
        Pasha Tatashin <pasha.tatashin@...een.com>
Subject: [PATCH v2 1/3] arm64: mm: Do not defer reserve_crashkernel() if only ZONE_DMA32

The kernel could be benefit due to BLOCK_MAPPINGS, see commit
031495635b46 ("arm64: Do not defer reserve_crashkernel() for
platforms with no DMA memory zones"), if only with ZONE_DMA32,
set arm64_dma_phys_limit to max_zone_phys(32) earlier in
arm64_memblock_init(), so platforms with just ZONE_DMA32 config
enabled will be benefit.

Cc: Vijay Balakrishna <vijayb@...ux.microsoft.com>
Cc: Pasha Tatashin <pasha.tatashin@...een.com>
Cc: Will Deacon <will@...nel.org>
Reviewed-by: Vijay Balakrishna <vijayb@...ux.microsoft.com>
Signed-off-by: Kefeng Wang <wangkefeng.wang@...wei.com>
---
 arch/arm64/mm/init.c | 23 +++++++++++++----------
 arch/arm64/mm/mmu.c  |  6 ++----
 2 files changed, 15 insertions(+), 14 deletions(-)

diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index 8ac25f19084e..fb01eb489fa9 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -65,8 +65,9 @@ EXPORT_SYMBOL(memstart_addr);
  * Memory reservation for crash kernel either done early or deferred
  * depending on DMA memory zones configs (ZONE_DMA) --
  *
- * In absence of ZONE_DMA configs arm64_dma_phys_limit initialized
- * here instead of max_zone_phys().  This lets early reservation of
+ * 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
+ * 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
  * mappings (greater than page-granularity) for all the memory bank rangs.
@@ -84,6 +85,7 @@ EXPORT_SYMBOL(memstart_addr);
  * Note: Page-granularity mapppings are necessary for crash kernel memory
  * range for shrinking its size via /sys/kernel/kexec_crash_size interface.
  */
+static phys_addr_t __ro_after_init dma32_phys_limit;
 #if IS_ENABLED(CONFIG_ZONE_DMA) || IS_ENABLED(CONFIG_ZONE_DMA32)
 phys_addr_t __ro_after_init arm64_dma_phys_limit;
 #else
@@ -160,11 +162,10 @@ static phys_addr_t __init max_zone_phys(unsigned int zone_bits)
 static void __init zone_sizes_init(unsigned long min, unsigned long max)
 {
 	unsigned long max_zone_pfns[MAX_NR_ZONES]  = {0};
-	unsigned int __maybe_unused acpi_zone_dma_bits;
-	unsigned int __maybe_unused dt_zone_dma_bits;
-	phys_addr_t __maybe_unused dma32_phys_limit = max_zone_phys(32);
-
 #ifdef CONFIG_ZONE_DMA
+	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);
@@ -173,8 +174,6 @@ static void __init zone_sizes_init(unsigned long min, unsigned long max)
 #endif
 #ifdef CONFIG_ZONE_DMA32
 	max_zone_pfns[ZONE_DMA32] = PFN_DOWN(dma32_phys_limit);
-	if (!arm64_dma_phys_limit)
-		arm64_dma_phys_limit = dma32_phys_limit;
 #endif
 	max_zone_pfns[ZONE_NORMAL] = max;
 
@@ -336,8 +335,12 @@ void __init arm64_memblock_init(void)
 
 	early_init_fdt_scan_reserved_mem();
 
-	if (!IS_ENABLED(CONFIG_ZONE_DMA) && !IS_ENABLED(CONFIG_ZONE_DMA32))
+	dma32_phys_limit = max_zone_phys(32);
+	if (!IS_ENABLED(CONFIG_ZONE_DMA)) {
+		if (IS_ENABLED(CONFIG_ZONE_DMA32))
+			arm64_dma_phys_limit = dma32_phys_limit;
 		reserve_crashkernel();
+	}
 
 	high_memory = __va(memblock_end_of_DRAM() - 1) + 1;
 }
@@ -385,7 +388,7 @@ 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 (IS_ENABLED(CONFIG_ZONE_DMA))
 		reserve_crashkernel();
 
 	memblock_dump_all();
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 626ec32873c6..23734481318a 100644
--- a/arch/arm64/mm/mmu.c
+++ b/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 (IS_ENABLED(CONFIG_ZONE_DMA))
 			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 && !IS_ENABLED(CONFIG_ZONE_DMA)) {
 		if (crashk_res.end) {
 			__map_memblock(pgdp, crashk_res.start,
 				       crashk_res.end + 1,
-- 
2.26.2