fadump: Reserve page-aligned boot_memory_size during fadump_reserve_mem

This patch refactors all CMA related initialization and alignment code
to within fadump_cma_init() which gets called in the end. This also means
that we keep [reserve_dump_area_start, boot_memory_size] page aligned
during fadump_reserve_mem(). Then later in fadump_cma_init() we extract the
aligned chunk and provide it to CMA. This inherently also fixes an issue in
the current code where the reserve_dump_area_start is not aligned
when the physical memory can have holes and the suitable chunk starts at
an unaligned boundary.

After this we should be able to call fadump_cma_init() independently
later in setup_arch() where pageblock_order is non-zero.

Suggested-by: Sourabh Jain <[email protected]>
Signed-off-by: Ritesh Harjani (IBM) <[email protected]>

arch/powerpc/kernel/fadump.c

@@ -80,7 +80,7 @@ static struct cma *fadump_cma;
  */
 static void __init fadump_cma_init(void)
 {
-	unsigned long long base, size;
+	unsigned long long base, size, end;
 	int rc;
 
 	/*
@@ -94,8 +94,24 @@ static void __init fadump_cma_init(void)
 	if (fw_dump.nocma || !fw_dump.boot_memory_size)
 		return;
 
+	/*
+	 * [base, end) should be reserved during early init in
+	 * fadump_reserve_mem(). No need to check this here as
+	 * cma_init_reserved_mem() already checks for overlap.
+	 * Here we give the aligned chunk of this reserved memory to CMA.
+	 */
 	base = fw_dump.reserve_dump_area_start;
 	size = fw_dump.boot_memory_size;
+	end = base + size;
+
+	base = ALIGN(base, CMA_MIN_ALIGNMENT_BYTES);
+	end = ALIGN_DOWN(end, CMA_MIN_ALIGNMENT_BYTES);
+	size = end - base;
+
+	if (end <= base) {
+		pr_err("%s: Too less memory to give to CMA\n", __func__);
+		return;
+	}
 
 	rc = cma_init_reserved_mem(base, size, 0, "fadump_cma", &fadump_cma);
 	if (rc) {
@@ -118,11 +134,11 @@ static void __init fadump_cma_init(void)
 	/*
 	 * So we now have successfully initialized cma area for fadump.
 	 */
-	pr_info("Initialized 0x%lx bytes cma area at %ldMB from 0x%lx "
+	pr_info("Initialized [0x%llx, %luMB] cma area from [0x%lx, %luMB] "
 		"bytes of memory reserved for firmware-assisted dump\n",
-		cma_get_size(fadump_cma),
-		(unsigned long)cma_get_base(fadump_cma) >> 20,
-		fw_dump.reserve_dump_area_size);
+		cma_get_base(fadump_cma), cma_get_size(fadump_cma) >> 20,
+		fw_dump.reserve_dump_area_start,
+		fw_dump.boot_memory_size >> 20);
 	return;
 }
 #else
@@ -556,13 +572,6 @@ int __init fadump_reserve_mem(void)
 	if (!fw_dump.dump_active) {
 		fw_dump.boot_memory_size =
 			PAGE_ALIGN(fadump_calculate_reserve_size());
-#ifdef CONFIG_CMA
-		if (!fw_dump.nocma) {
-			fw_dump.boot_memory_size =
-				ALIGN(fw_dump.boot_memory_size,
-				      CMA_MIN_ALIGNMENT_BYTES);
-		}
-#endif
 
 		bootmem_min = fw_dump.ops->fadump_get_bootmem_min();
 		if (fw_dump.boot_memory_size < bootmem_min) {