From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wm1-f47.google.com (mail-wm1-f47.google.com [209.85.128.47]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6516E192D8A for ; Fri, 2 Jan 2026 08:15:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.47 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767341707; cv=none; b=GiHhbfQ+TwiY3YzGE1xO/qKRGlJ+kNzgfqpqBF6n3Ppdrng3yNXQvwa22MnzWmWYc85nLYMiZwKEwdznkI20+LPwOFf9Gl8VmK2ESPxdTKGXtosgcBrkO2g/hRGAgfHtCr3ljXAN4yCvKoTTjDxN3QetvHlmT5tYJnZ/wLUzvmg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767341707; c=relaxed/simple; bh=pR9J2JcpyuSslYDA7lsLX4ZhILZRZva1Jx7LQCRL2xc=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=bo9VcTY6+fiQVK43tNWQVbJp54c6p/3D6i8gQ16FcTQP4pcOy4J/qkuNbJGYAJl5Q7TM1j/B8YKTB2PPeXpo7Np/Z6HR2Ml8G/LEKb77pDsg1VID6Q5HkOlUzS2Nzf9kTtBBIXvggrFPIQk83FWGRqRGKBXfXtYD3eJZjpcDNJU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=suse.com; spf=pass smtp.mailfrom=suse.com; dkim=pass (2048-bit key) header.d=suse.com header.i=@suse.com header.b=YA76nKi/; arc=none smtp.client-ip=209.85.128.47 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=suse.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=suse.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=suse.com header.i=@suse.com header.b="YA76nKi/" Received: by mail-wm1-f47.google.com with SMTP id 5b1f17b1804b1-477aa91e75dso12208675e9.3 for ; Fri, 02 Jan 2026 00:15:03 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=google; t=1767341702; x=1767946502; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:subject:cc:to:from:date:from:to:cc:subject:date :message-id:reply-to; bh=7B5OROvqw/DgiaRfLYZJf4GjF/wj6CLJOtpsQ8Z+Uq0=; b=YA76nKi/w+4r6QrU3u2zf5Le8V9XRZBLFbZgcDqg8nvt9MckDoEaO8By8k5rFaH2zj M6FOWUp+8LwZBjF7Ct+EYIO0kH0S0v+Pr9wSVpl4cXLp1lFB/7/Pb3+7EkRYFZ3ouqef b8TA2l7ZzYNtFHMUb7pVDcW0ZmWyV8GwubCAvrstaOiHAncUBTCHGnjdqJUtd1u693Nf pm12hnFgGAbipqxoZBPGus+ExXjFykcTzIXHpoBAw8wzK/IcFi5XxjN/gsygR6pDcVF0 P1iYMU4BuJYFaPN7BknV7Vy3fKB9GXy/u40sq+1UrdlhP1knI9/5NYPkaXLxDyogj33o q9Jw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1767341702; x=1767946502; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:subject:cc:to:from:date:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to; bh=7B5OROvqw/DgiaRfLYZJf4GjF/wj6CLJOtpsQ8Z+Uq0=; b=HP9xQy8Dxp3GeOAK1/Y8VXvSccEkw2TB+IW77Lg35PQGfz4qj4L+6UUEq4PuZGgUol AvohmR31ohiBkQfsznRnB/kH4GN14VMq/5o1j0MaC3XzzDqjkTjqRLpSfnSdY+pIEa3a OUMY9HdZYNVdFZ6XKeHfg8+JF75a4zN9/ZWg9Pn5v+zWyGEqHUInRBm4792FIOe0NUdQ ia/85I5aGsdgWA2N6ux+WgWcCphdTUvIFUiX8rm/x/LH89UD90dF99kFH7gQIywqzAsz 12BnSva60/CleU6+2nvf+KLkxOgt1oZ3wrptL2UgSIp+43A8XRJ6V8+Ck3o83ZEvk7LB v0rw== X-Forwarded-Encrypted: i=1; AJvYcCXflG+DbpkGZW+GGU/hokGbNd7BL34pxk9aEIlITkddJPMHAYifOKhnKFtJsMbFoTGguQ7jchk=@vger.kernel.org X-Gm-Message-State: AOJu0YzaDnrb4EWUzAaMI3bWbagmas0WILqOsUf6fOmifr5HTFie4Dha vJOHKoAY8x8H3fNFCb33j745qM2Wa37ZJzvrtt5OU6BsIphqWflkq6qM8m93+CKtKk4= X-Gm-Gg: AY/fxX67dbroSIlgD4JW+AyAhLrSeYlfE3p4adLzUwuHnDf9qJwaJ/Fe1eSB8mrOAyQ vhdZWWFQ4Jaygn2gOtureVwkSWCsHQbRWktZTkt4cY1rny2S0JNc8wD33AQ9AgRSbM4EiZajG1E Cp3jiDaq27mgioPSu7QJn8ndpHDRNxLztRdwaO/KK0DrEYmpnl6AAt9OJ8ZcxHMrnGn3zkBpfec rTU6+YNrJYsKU1pisE3wAA31bBOzE0JZakOrB+8SvBp5OrCxOiecdFrNm5PboZHQwgzyYtItlyx 4hmgsOHft9CPeLWJnyzXWALgV7KYKXZ3KViXKHu9Zn/sZQdxaLvNL0mTWANnLaHxDBn0bIe2dmI Q9IoDqK7p/QoVGgLQ5jQnAuRETFDVD7lyzXItXprM7rFM5hqzMjJmHaQZRfYOq0DI4yYuvDiEUH yx0CSQWUVtTE+vwFW9X6rYu8uixhQ/w1p7I5QEUSNI2SuWtn5kFm3dnGE6a4LkQhExdRPLYqm8d Wl2 X-Google-Smtp-Source: AGHT+IEG7/UqWg/6ELIcyq0mVb3xfMQn4RI8cpiRrR5W4zXnA35xM+TJgjTRoe1XllkShxIti5fDKg== X-Received: by 2002:a05:600c:3151:b0:477:a203:66dd with SMTP id 5b1f17b1804b1-47d197f69demr322547935e9.2.1767341702410; Fri, 02 Jan 2026 00:15:02 -0800 (PST) Received: from mordecai (dynamic-2a00-1028-83b8-1e7a-3010-3bd6-8521-caf1.ipv6.o2.cz. [2a00:1028:83b8:1e7a:3010:3bd6:8521:caf1]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-47be27b0d5asm792930555e9.13.2026.01.02.00.15.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 02 Jan 2026 00:15:01 -0800 (PST) Date: Fri, 2 Jan 2026 09:14:59 +0100 From: Petr Tesarik To: "Michael S. Tsirkin" Cc: linux-kernel@vger.kernel.org, Cong Wang , Jonathan Corbet , Olivia Mackall , Herbert Xu , Jason Wang , Paolo Bonzini , Stefan Hajnoczi , Eugenio =?UTF-8?B?UMOpcmV6?= , "James E.J. Bottomley" , "Martin K. Petersen" , Gerd Hoffmann , Xuan Zhuo , Marek Szyprowski , Robin Murphy , Stefano Garzarella , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Leon Romanovsky , Jason Gunthorpe , linux-doc@vger.kernel.org, linux-crypto@vger.kernel.org, virtualization@lists.linux.dev, linux-scsi@vger.kernel.org, iommu@lists.linux.dev, kvm@vger.kernel.org, netdev@vger.kernel.org Subject: Re: [PATCH RFC 01/13] dma-mapping: add __dma_from_device_align_begin/end Message-ID: <20260102091459.6bec60c2@mordecai> In-Reply-To: <20251231154722-mutt-send-email-mst@kernel.org> References: <20251231150159.1779b585@mordecai> <20251231154722-mutt-send-email-mst@kernel.org> X-Mailer: Claws Mail 4.3.1 (GTK 3.24.51; x86_64-suse-linux-gnu) Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Wed, 31 Dec 2025 15:48:26 -0500 "Michael S. Tsirkin" wrote: > On Wed, Dec 31, 2025 at 03:01:59PM +0100, Petr Tesarik wrote: > > On Tue, 30 Dec 2025 05:15:46 -0500 > > "Michael S. Tsirkin" wrote: > > > > > When a structure contains a buffer that DMA writes to alongside fields > > > that the CPU writes to, cache line sharing between the DMA buffer and > > > CPU-written fields can cause data corruption on non-cache-coherent > > > platforms. > > > > > > Add __dma_from_device_aligned_begin/__dma_from_device_aligned_end > > > annotations to ensure proper alignment to prevent this: > > > > > > struct my_device { > > > spinlock_t lock1; > > > __dma_from_device_aligned_begin char dma_buffer1[16]; > > > char dma_buffer2[16]; > > > __dma_from_device_aligned_end spinlock_t lock2; > > > }; > > > > > > When the DMA buffer is the last field in the structure, just > > > __dma_from_device_aligned_begin is enough - the compiler's struct > > > padding protects the tail: > > > > > > struct my_device { > > > spinlock_t lock; > > > struct mutex mlock; > > > __dma_from_device_aligned_begin char dma_buffer1[16]; > > > char dma_buffer2[16]; > > > }; > > > > This works, but it's a bit hard to read. Can we reuse the > > __cacheline_group_{begin, end}() macros from ? > > Something like this: > > > > #define __dma_from_device_group_begin(GROUP) \ > > __cacheline_group_begin(GROUP) \ > > ____dma_from_device_aligned > > #define __dma_from_device_group_end(GROUP) \ > > __cacheline_group_end(GROUP) \ > > ____dma_from_device_aligned > > > > And used like this (the "rxbuf" group id was chosen arbitrarily): > > > > struct my_device { > > spinlock_t lock1; > > __dma_from_device_group_begin(rxbuf); > > char dma_buffer1[16]; > > char dma_buffer2[16]; > > __dma_from_device_group_end(rxbuf); > > spinlock_t lock2; > > }; > > > > Petr T > > Made this change, and pushed out to my tree. > > I'll post the new version in a couple of days, if no other issues > surface. FTR except my (non-critical) suggestions for PATCH 5/13, the updated series looks good to me. Thank you! Petr T