From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2E5F43ACA43; Mon, 14 Sep 2026 07:03:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789369418; cv=none; b=uP5zj5pmOpCi0UAZc/VAxCNVOtkB3foxkZBl6/njTJRi+YVb+i6WAwipLUWy72HI6hzuAww9U043iY5GBkrxg7Wu8hV9fSY3LFVaXCsb+xXPT3RIsmkxZ6q02Rb0w057UTf2+C8qCi1ThKlhsEiHfGY6RhAqduWgNhUEuOEB/Jc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789369418; c=relaxed/simple; bh=+SASFzDMBNGBSsPiJbYQAj6oJSNY3PejaCNk2W0IpY8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ZC78iQox1hHiHTDl+mHpKiCwoUoafg3nB/4OjrZbYnfvsI+lfs0dqG9rRU5o3esfy/SEyKkjvHsOFD1Fk+nONUedupHGDFSw1uykic1XD/yRIlp+tD4Bz5zCKbCcachoCVGXgiNSzrVRwpRvkib7X+hHVNGfQhl9Spz/nKZ0uXI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=JE1P8nt2; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="JE1P8nt2" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 489181F000FF; Mon, 14 Sep 2026 07:03:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789369416; bh=WEcbhQazoSj1y/YavhLCyevXiP51++W+4wFyMfPfLH8=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=JE1P8nt2+GATNQTa6sTYnl9jTgx15El0FdbS10klL/OAbcC8zGQdc3X2a12aswWUQ ugSnP+fGMPaGDy3B6IGUKT7DPxiW5tFG84lqLNP2447KfWNNm5vAZVc0+vfLU/1joS rLlBbE1Od/kwZi0Zsm8Mz/fdEWcVXoW1Gf2Q2fb7LiECmYDcqPI/pGkJZzte7hyYAq tZj1Xx65LGLQ22zHRcP0bBcIKlA1xCYv/c+mccHOq140cRCtt5VOD/PjpM0xEXmOhE rQcF6J7GxnekCBSZLyX1nhfSJmRyRKpxd8uGz1HHqfFlnfFDXKgzuH0ynjBavxFC9h BY/QWR4Q43auw== 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 v4 5/5] dma: swiotlb: Remove SWIOTLB_ANY Date: Mon, 14 Sep 2026 12:31:34 +0530 Message-ID: <20260914070135.313337-6-aneesh.kumar@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260914070135.313337-1-aneesh.kumar@kernel.org> References: <20260914070135.313337-1-aneesh.kumar@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit swiotlb pools are currently allocated below the architecture's low address limit by default. SWIOTLB_ANY overrides this and permits allocation anywhere in directly mapped memory. SWIOTLB_INIT_ADDRESSING_LIMIT now explicitly identifies callers which need a pool that is reachable by devices with limited DMA addressing. Use it as the placement constraint and remove SWIOTLB_ANY. This changes the default behavior for callers which do not set either flag. Previously, omitting SWIOTLB_ANY placed the default pool below the architecture's low address limit and also constrained dynamically allocated pools to the same range. After this change, omitting SWIOTLB_INIT_ADDRESSING_LIMIT permits both static and dynamic pools to use any directly mapped memory. Signed-off-by: Aneesh Kumar K.V (Arm) --- Documentation/core-api/swiotlb.rst | 8 ++++---- arch/powerpc/mm/mem.c | 6 ++++-- arch/s390/mm/init.c | 2 +- arch/x86/kernel/pci-dma.c | 2 +- include/linux/swiotlb.h | 7 +++---- kernel/dma/swiotlb.c | 17 ++++++----------- 6 files changed, 19 insertions(+), 23 deletions(-) diff --git a/Documentation/core-api/swiotlb.rst b/Documentation/core-api/swiotlb.rst index 71b4e4c27eb5..06d9f88fdf7b 100644 --- a/Documentation/core-api/swiotlb.rst +++ b/Documentation/core-api/swiotlb.rst @@ -148,10 +148,10 @@ may also be adjusted due to other conditions, such as running in a CoCo VM, as described above. If CONFIG_SWIOTLB_DYNAMIC is enabled, additional pools may be allocated later in the life of the system. Each pool must be a contiguous range of physical -memory. The default pool is allocated below the 4 GiB physical address line so -it works for devices that can only address 32-bits of physical memory (unless -architecture-specific code provides the SWIOTLB_ANY flag). In a CoCo VM, the -pool memory must be decrypted before swiotlb is used. +memory. The default pool is allocated below the architecture's low address +limit when it is needed for devices with limited DMA addressing. Otherwise, +it may be allocated anywhere in directly mapped memory. In a CoCo VM, the pool +memory must be decrypted before swiotlb is used. Each pool is divided into "slots" of size IO_TLB_SIZE, which is 2 KiB with current definitions. IO_TLB_SEGSIZE contiguous slots (128 slots) constitute diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c index 006ed41097e9..1bdea6c03848 100644 --- a/arch/powerpc/mm/mem.c +++ b/arch/powerpc/mm/mem.c @@ -295,9 +295,11 @@ void __init arch_mm_preinit(void) /* * Since the guest memory is inaccessible to the host, * devices always need to use the SWIOTLB buffer for DMA - * even if dma_capable() says otherwise. + * even if dma_capable() says otherwise. The hypervisor has + * no addressing limitation, so the buffer may be allocated + * anywhere. */ - ppc_swiotlb_flags |= SWIOTLB_ANY; + ppc_swiotlb_flags &= ~SWIOTLB_INIT_ADDRESSING_LIMIT; } /* diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c index 78f507e24ceb..ce10292447f1 100644 --- a/arch/s390/mm/init.c +++ b/arch/s390/mm/init.c @@ -166,7 +166,7 @@ static void __init pv_init(void) virtio_set_mem_acc_cb(virtio_require_restricted_mem_acc); /* make sure bounce buffers are shared */ - swiotlb_init(SWIOTLB_VERBOSE | SWIOTLB_ANY); + swiotlb_init(SWIOTLB_VERBOSE); swiotlb_update_mem_attributes(); } diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c index cd6dd151d634..a8070cae8253 100644 --- a/arch/x86/kernel/pci-dma.c +++ b/arch/x86/kernel/pci-dma.c @@ -89,7 +89,7 @@ static void __init pci_xen_swiotlb_init(void) /* Xen can use a SWIOTLB pool anywhere in directly mapped memory. */ x86_swiotlb_flags &= ~(SWIOTLB_INIT_ADDRESSING_LIMIT | SWIOTLB_INIT_FORCE_DISABLE); - x86_swiotlb_flags |= SWIOTLB_INIT_REMAP | SWIOTLB_ANY; + x86_swiotlb_flags |= SWIOTLB_INIT_REMAP; swiotlb_init_remap(x86_swiotlb_flags, xen_swiotlb_fixup); dma_ops = &xen_swiotlb_dma_ops; if (IS_ENABLED(CONFIG_PCI)) diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h index ef7a776ee508..77542f107b3f 100644 --- a/include/linux/swiotlb.h +++ b/include/linux/swiotlb.h @@ -15,13 +15,12 @@ struct page; struct scatterlist; #define SWIOTLB_VERBOSE (1 << 0) /* verbose initialization */ -#define SWIOTLB_ANY (1 << 1) /* allow any memory for the buffer */ /* Initialize a default-sized pool for devices with limited DMA addressing. */ -#define SWIOTLB_INIT_ADDRESSING_LIMIT (1 << 2) +#define SWIOTLB_INIT_ADDRESSING_LIMIT (1 << 1) /* Initialize a default-sized pool that requires architecture remapping. */ -#define SWIOTLB_INIT_REMAP (1 << 3) +#define SWIOTLB_INIT_REMAP (1 << 2) /* Do not initialize a pool unless SWIOTLB is explicitly required. */ -#define SWIOTLB_INIT_FORCE_DISABLE (1 << 4) +#define SWIOTLB_INIT_FORCE_DISABLE (1 << 3) /* * Maximum allowable number of contiguous slabs to map, diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c index 6695da682f96..f8a77926b8b0 100644 --- a/kernel/dma/swiotlb.c +++ b/kernel/dma/swiotlb.c @@ -448,15 +448,10 @@ static void __init *swiotlb_memblock_alloc(unsigned long nslabs, size_t bytes = PAGE_ALIGN(nslabs << IO_TLB_SHIFT); void *tlb; - /* - * By default allocate the bounce buffer memory from low memory, but - * allow to pick a location everywhere for hypervisors with guest - * memory encryption. - */ - if (flags & SWIOTLB_ANY) - tlb = memblock_alloc(bytes, PAGE_SIZE); - else + if (flags & SWIOTLB_INIT_ADDRESSING_LIMIT) tlb = memblock_alloc_low(bytes, PAGE_SIZE); + else + tlb = memblock_alloc(bytes, PAGE_SIZE); if (!tlb) { pr_warn("%s: Failed to allocate %zu bytes tlb structure\n", @@ -604,10 +599,10 @@ void __init swiotlb_init_remap(unsigned int flags, #ifdef CONFIG_SWIOTLB_DYNAMIC if (!remap) io_tlb_default_mem.can_grow = true; - if (flags & SWIOTLB_ANY) - io_tlb_default_mem.phys_limit = virt_to_phys(high_memory - 1); - else + if (flags & SWIOTLB_INIT_ADDRESSING_LIMIT) io_tlb_default_mem.phys_limit = ARCH_LOW_ADDRESS_LIMIT; + else + io_tlb_default_mem.phys_limit = virt_to_phys(high_memory - 1); #endif /* if we have host or guest memory encryption */ -- 2.43.0