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 925B03EBF02 for ; Mon, 14 Sep 2026 07:50:50 +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=1789372251; cv=none; b=ZEzu3ALufzFGQxgCY9+tbiQmjshP/gO3+fj9QCz32PvY+ppY5SRqv+Ft11BqCJueYY3qOb5RaukpXCfVDcSgF5KmhDD+Z3t/sxctQ/e6627gQgIL0urWSwI2ZqSzFMpIgZuF9HdKXxZIDqIByJQQI+/Odk6XKvfv/BE1tP3ro3A= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789372251; c=relaxed/simple; bh=kRD8cpyBRznT2LiwISZzlm6gs4Uw0AzTTY6Uldg3OK8=; h=From:Subject:To:Cc:In-Reply-To:References:Content-Type:Date: Message-Id; b=s/d0ZTCDQJ/Ph0FIhNTfaQ79l2g963ZDpZqeD6sKFL6Gd4ITliuexPORIONoi7CpewsaA3tCSGPFR+CS0EQ92A7V4J0yujfwD542BYrm+Ofo0DP05DbIPkMID/8/cLPC4paZdKITbZDWy6xvL1jQMaKMi20QofdJBzF6FpN8reg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=h3xX5RF6; 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="h3xX5RF6" Received: by smtp.kernel.org (Postfix) with ESMTPSA id DA9141F00898; Mon, 14 Sep 2026 07:50:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789372250; bh=kRD8cpyBRznT2LiwISZzlm6gs4Uw0AzTTY6Uldg3OK8=; h=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date; b=h3xX5RF6msHrRf5nfqqSyzYZj9F1RgWBdW0+SeGjJjnYrV2TrbCG5thDbsF8Jo+VL 0ByrhYEyk3dhPH1rGUArfyWRxEF9KQh4PWR64FzN2tdbr4RCv/cCxoLLG4b7v/ellp AV3LMddBK3mEvjy39MPMmGDbRmtIk8E/jzy1WuncRFJAWXjidLs1Pvi+PU2k+A6WtS arKvkQGaHYAkVYxNl7BHn+khemmHsqo+ANsZuWBdkYAa2tn0XCZYpwfUYa5GU0ime9 2LPHxTTGMzdh+f4yegwnz/BAECp413XeW5tXPEHylD1AG5rcLORoKyg7pwqUEfIvab klxvkI5jDyzDg== From: sashiko-bot@kernel.org Subject: Re: [PATCH v4 4/5] dma: swiotlb: Add an overridable architecture pool opt-out Reply-To: sashiko-reviews@lists.linux.dev To: =?utf-8?b?QW5lZXNoIEt1bWFyIEsuViAoQXJtKQ==?= Cc: linux-s390@vger.kernel.org, "Christian Borntraeger" , "Vasily Gorbik" , "Alexander Gordeev" , "Heiko Carstens" In-Reply-To: <20260914070135.313337-5-aneesh.kumar@kernel.org> References: <20260914070135.313337-1-aneesh.kumar@kernel.org> <20260914070135.313337-5-aneesh.kumar@kernel.org> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Mon, 14 Sep 2026 07:50:49 +0000 Message-Id: <20260914075049.DA9141F00898@smtp.kernel.org> Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: > On x86, iommu=3Doff historically prevented SWIOTLB initialization by not > setting SWIOTLB_INIT_ADDRESSING_LIMIT. This overloads that flag: it > controls both whether a pool is selected and where the pool is > allocated. If another requirement, swiotlb=3Dforce selects a pool > independently, omitting SWIOTLB_INIT_ADDRESSING_LIMIT may place it above > the addressable range of devices which need bounce buffering. >=20 > Add SWIOTLB_INIT_FORCE_DISABLE to let an architecture opt out of normal > pool initialization without discarding the pool placement constraints. >=20 > Unlike swiotlb_force_disable, which is set by swiotlb=3Dnoforce and > unconditionally prevents pool initialization, the new flag is an > architecture default. Explicit requirements such as memory encryption, > architecture remapping, or swiotlb=3Dforce take precedence over it. >=20 > iommu=3Dsoft retains SWIOTLB_INIT_ADDRESSING_LIMIT because it requests > software bounce buffering for devices whose DMA masks cannot address all > system memory. Such devices must be able to reach the bounce pool. >=20 > Clear both flags for Xen because Xen explicitly requires a remapped > SWIOTLB pool and may allocate it anywhere in directly mapped memory. >=20 > With no override, iommu=3Doff disables both hardware IOMMU translation and > SWIOTLB bouncing. Direct DMA remains available; mappings outside a > device's addressable range fail instead of being bounced. >=20 > Signed-off-by: Aneesh Kumar K.V (Arm) Sashiko has reviewed this patch and found no issues. It looks great! --=20 Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/20260914070135.3133= 37-1-aneesh.kumar@kernel.org?part=3D4