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Mon, 21 Sep 2026 06:37:35 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 096271F0089B; Mon, 21 Sep 2026 06:37:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789972655; bh=K+b48+bUbw9Zp4TfNEQmI2aqQxUfqoVbbM+1xt10BLE=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=i1lXqpcv+CPfidLk/96Fek4pilhGGmkGJ7Nr4F2IHCJJ6FuqR0PTsYqukoIkeg7gt XEB9TgelNnrAWy/D50/VDHEv9mauRfXNtb4u80xZDG/3sIG+NIxMhNyTAwCt1FY/O4 758rYhWOpB4ZClrdEKI2yugVJBN9iGbpxqHZv8446bbnmfrCn+S1xVmOXvWyIe/17B h8gETpRxuPbaozRiXDcHU9TPq4ltfM6zu83g6IuiarcsJqrjY4S8y1tgFU+5lKC1rv ZuU3QfyH0StC3QqvAVG4LCTAwEFMRG1wXe65yq7rUqmD2xPy6QvChT0gB5/jz8a/Bb JJoEXmVRzmg5Q== From: "Aneesh Kumar K.V (Arm)" To: iommu@lists.linux.dev, linux-kernel@vger.kernel.org Cc: "Aneesh Kumar K.V (Arm)" , Robin Murphy , Marek Szyprowski , Will Deacon , Marc Zyngier , Steven Price , Suzuki K Poulose , Catalin Marinas , Jiri Pirko , Jason Gunthorpe , Mostafa Saleh , Petr Tesarik , Alexey Kardashevskiy , Dan Williams , Xu Yilun , Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , "Christophe Leroy (CS GROUP)" , Alexander Gordeev , Gerald Schaefer , Heiko Carstens , Vasily Gorbik , Christian Borntraeger , Sven Schnelle , Russell King , Huacai Chen , Thomas Bogendoerfer , Jiaxun Yang , Paul Walmsley , Palmer Dabbelt , Albert Ou , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , linux-arm-kernel@lists.infradead.org, loongarch@lists.linux.dev, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, x86@kernel.org Subject: [PATCH v5 3/6] dma: swiotlb: Centralize minimal pool sizing Date: Mon, 21 Sep 2026 12:06:25 +0530 Message-ID: <20260921063628.362078-4-aneesh.kumar@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260921063628.362078-1-aneesh.kumar@kernel.org> References: <20260921063628.362078-1-aneesh.kumar@kernel.org> X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit A default SWIOTLB pool used only for unaligned kmalloc bouncing can be smaller than one required for limited DMA addressing. Arm64 and RISC-V currently implement this sizing independently, using 1 MiB of SWIOTLB space per GiB of RAM. The SWIOTLB core now identifies this case with SWIOTLB_POOL_MINIMAL. Size that policy in swiotlb_adjust_pool_size() and remove the architecture-specific adjustments. Explicit swiotlb= sizing remains unchanged because swiotlb_adjust_size() preserves a user-configured size. Signed-off-by: Aneesh Kumar K.V (Arm) --- arch/arm64/mm/init.c | 11 ----------- arch/riscv/mm/init.c | 4 ---- kernel/dma/swiotlb.c | 11 ++++++++++- 3 files changed, 10 insertions(+), 16 deletions(-) diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c index 7d51fb5f5a71..95075b5c8207 100644 --- a/arch/arm64/mm/init.c +++ b/arch/arm64/mm/init.c @@ -340,17 +340,6 @@ void __init arch_mm_preinit(void) { unsigned int flags = SWIOTLB_VERBOSE; - if (max_pfn <= PFN_DOWN(arm64_dma_phys_limit)) { - /* - * 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)); - } - if (max_pfn > PFN_DOWN(arm64_dma_phys_limit)) flags |= SWIOTLB_INIT_ADDRESSING_LIMIT; diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c index e0e4c103d603..96856114b387 100644 --- a/arch/riscv/mm/init.c +++ b/arch/riscv/mm/init.c @@ -183,10 +183,6 @@ void __init arch_mm_preinit(void) * memory when DRAM starts above dma32_phys_limit. Allocate * ~1 MB per 1 GB 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_flags |= SWIOTLB_ANY; } diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c index 8f86deb25be2..f368a73f4ed0 100644 --- a/kernel/dma/swiotlb.c +++ b/kernel/dma/swiotlb.c @@ -483,9 +483,18 @@ static bool __init swiotlb_kmalloc_needs_bounce(void) static void __init swiotlb_adjust_pool_size(enum swiotlb_pool_policy policy) { + if (swiotlb_default_size_changed()) + return; + switch (policy) { - case SWIOTLB_POOL_MINIMAL: + case SWIOTLB_POOL_MINIMAL: { + unsigned long size; + + /* Use 1MB per 1GB of RAM for kmalloc() bouncing. */ + size = DIV_ROUND_UP(memblock_phys_mem_size(), 1024); + swiotlb_adjust_size(min(swiotlb_size_or_default(), size)); break; + } case SWIOTLB_POOL_CC_GUEST: break; case SWIOTLB_POOL_NONE: -- 2.43.0