From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 C140C2AE69 for ; Fri, 20 Sep 2024 14:04:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.137.202.133 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1726841050; cv=none; b=bsIdPaTxB7hU+zNFUCnXR4OhO1VTXOBuTN6HOREUV8FzPSqiAtOHqzopWFm7ZLU9YUulCUqVzgq0+yxyhaQ5Cl1B/BFQXxWYq3dHhRFL4oULPSeZKLPggy0b/OgKl+5bEqRzikNC3wEsR06JCtCSLg/iN3lIhy251q4Qxn4PWZo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1726841050; c=relaxed/simple; bh=INwMnjrw6XY2PUL5tCabPluVjGp8LD61b2twB3W7CaM=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=XiSwDMfi8bpq7+UgZxY1Xdayi2DtL0/t0FXvmCqssmCZ9Ak64rDsE7P0smWRXH6qSx5tupZeuw7yZ20e4pCAPrLAhLnxzOKEIWl5DIDyCM3Ua37lsii/SVu1dst/a+9ycIP4T3ZDBFZSm5Lj1RNN5WCApisKRQWrwu2PjWYlYTY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=bombadil.srs.infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=RnEP+KJJ; arc=none smtp.client-ip=198.137.202.133 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=bombadil.srs.infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="RnEP+KJJ" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=RCwlKLEJXQ81sm67JF7/OQA8EjktrgnBwq8TDvkYkrU=; b=RnEP+KJJVour4Wz2TFpMO2awow dciUCqYfTUUpPqPx7hl88uS9bw0ASNFt/qia735KVxZWkE6iY7UcFeRxg2MMbWigSzKi2JVQN8ser GXOrClbTLj1jU6mwSBmyI85Ix8U6HXDjNV9Sac0L9HZ4DqIOcDp/Xi6hp/cHch1wbHeGpcfQtFDOJ gC/8LOnfu7Idg1caicV3Atx0ieiH08dgd9cA8aKgu3NDjItfoL3Ij50BjqaejBPnRwekqSSIWQjNa +qWNox54k/NzEOmU9ohjHe8/UaBk2gxFT3rpO/vowzS4gGzDH/ate3NT0aekeLh1A4e2pMBD3ozJE yWdDL9zw==; Received: from hch by bombadil.infradead.org with local (Exim 4.98 #2 (Red Hat Linux)) id 1sreEw-0000000CK7O-25DY; Fri, 20 Sep 2024 14:04:06 +0000 Date: Fri, 20 Sep 2024 07:04:06 -0700 From: Christoph Hellwig To: Vladimir Kondratiev Cc: Paul Walmsley , Palmer Dabbelt , Albert Ou , Andrew Morton , linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH] riscv: make ZONE_DMA32 optional Message-ID: References: <20240827113611.537302-1-vladimir.kondratiev@mobileye.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240827113611.537302-1-vladimir.kondratiev@mobileye.com> X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html On Tue, Aug 27, 2024 at 02:36:11PM +0300, Vladimir Kondratiev wrote: > It is not necessary any RISCV platform has ZONE_DMA32. That is an odd statement. The point of ZONE_DMA32 is to make sure that drivers can always allocate 32-bit DMAable memory, and without ZONE_DMA32 that is very hard to provide unless you always have an IOMMU. > Example - if platform has no DRAM in [0..4G] region, > it will report failure like below each boot. ZONE_DMA32 is supposed to contain the 32-bit dma addressable memory, not 32-bit physical. Take a look at the changes that just went into Linus' tree for that.