From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org 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.lore.kernel.org (Postfix) with ESMTPS id 5677FC54EAA for ; Fri, 27 Jan 2023 07:08:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=f1CIItkJtPT1YW+09t61tP8MYs4VYqL9MjZheWlAI40=; b=Kpr3fgEqJK6wrY A1iK+GpmApYIeF3tW+Ii2eXgKA3gq2vyLPQYHIHaHZB9NCSuifofhSLpGX3wvOWu5+usqAKSCzZcZ On99aMPOkIg7z2FjoZDtIDDAHIsGOoKB+HjC9yy+nlUYx8khmCn9Mwe3okgXwYt1FGylHIDlkepaR Q1t95FBgODOsWCMoffVLYbi6PqF2UHfhF4BmIhdh37xy0+IRWoRY3jsROkgTmL4FfXnNkqMOa5xaY EaWw6W65E4LlEgs2R3MywBXpOuFCGlyxvhWY/q7man41fYcg+lsBjudKJKCvqOpzj/qtijdjIgIMb 9JMUI8xBUN6zOaWAoaRg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1pLIpN-00DPm6-0C; Fri, 27 Jan 2023 07:07:13 +0000 Received: from verein.lst.de ([213.95.11.211]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1pLIpJ-00DPl2-L7 for linux-arm-kernel@lists.infradead.org; Fri, 27 Jan 2023 07:07:11 +0000 Received: by verein.lst.de (Postfix, from userid 2407) id 3621568D09; Fri, 27 Jan 2023 08:07:05 +0100 (CET) Date: Fri, 27 Jan 2023 08:07:05 +0100 From: Christoph Hellwig To: "H. Peter Anvin" Cc: Christoph Hellwig , Dave Hansen , Georgi Djakov , catalin.marinas@arm.com, will@kernel.org, dave.hansen@linux.intel.com, luto@kernel.org, peterz@infradead.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, m.szyprowski@samsung.com, robin.murphy@arm.com, linux-arm-kernel@lists.infradead.org, iommu@lists.linux.dev, linux-kernel@vger.kernel.org, djakov@kernel.org Subject: Re: [RFC] mm: Allow ZONE_DMA32 to be disabled via kernel command line Message-ID: <20230127070705.GA4180@lst.de> References: <20230126164352.17562-1-quic_c_gdjako@quicinc.com> <20230127063555.GA3300@lst.de> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.17 (2007-11-01) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230126_230709_843093_595C03EC X-CRM114-Status: GOOD ( 13.18 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, Jan 26, 2023 at 10:52:43PM -0800, H. Peter Anvin wrote: > >If people want ZONE_DMA32 to go away we need something to replace > >it first, like a large enough CMA region in the 32-bit addressable > >range. > > Not to mention all kinds of odd masks like 30, 31, 39, 40, 46, ... bits. Yes. Out of those all >= 32 are falling straight into ZONE_DM32, the lower ones we do a first try in ZONE_DMA32 and then fall back to ZONE_DMA. <= 29 mask OTOH are really rate in modern systems for actual devices. So with a CMA region for what is currently ZONE_DMA and one for the first 1G we'd probably cover most of what's actually needed for x86_64. Of course on 32-bit architetures things become a lot more complicated due to highmem. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel