Subject: [PATCH 1/3] arm64/mm: Simplify SWIOTLB setup in arch_mm_preinit()

From: Mostafa Saleh <[email-masked]>
Date: Wed, 3 Jun 2026 11:05:20 +0000

At the moment, arch_mm_preinit() checks if the system has limited
addressing or is running under CCA to enable SWIOTLB, only after to
be forced to true anyway if it was false due to
CONFIG_DMA_BOUNCE_UNALIGNED_KMALLOC being unconditionally true for
arm64.

Simplify this logic, by making it clear that SWIOTLB is always used
but its size depends on the address layout of the system.

Signed-off-by: Mostafa Saleh <[email-masked]>
---
 arch/arm64/mm/init.c | 11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index 97987f850a33..fcc9c05a8fe6 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -336,25 +336,22 @@ void __init arch_setup_zero_pages(void)
 void __init arch_mm_preinit(void)
 {
 	unsigned int flags = SWIOTLB_VERBOSE;
-	bool swiotlb = max_pfn > PFN_DOWN(arm64_dma_phys_limit);
+	bool limited_addressing = max_pfn > PFN_DOWN(arm64_dma_phys_limit);
 
 	if (is_realm_world()) {
-		swiotlb = true;
 		flags |= SWIOTLB_FORCE;
-	}
-
-	if (IS_ENABLED(CONFIG_DMA_BOUNCE_UNALIGNED_KMALLOC) && !swiotlb) {
+	} else if (!limited_addressing) {
 		/*
 		 * If no bouncing needed for ZONE_DMA, reduce the swiotlb
 		 * buffer for kmalloc() bouncing to 1MB per 1GB of RAM.
 		 */
 		unsigned long size =
 			DIV_ROUND_UP(memblock_phys_mem_size(), 1024);
+
 		swiotlb_adjust_size(min(swiotlb_size_or_default(), size));
-		swiotlb = true;
 	}
 
-	swiotlb_init(swiotlb, flags);
+	swiotlb_init(true, flags);
 
 	/*
 	 * Check boundaries twice: Some fundamental inconsistencies can be
-- 
2.54.0.1032.g2f8565e1d1-goog