From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <owner-linux-mm@kvack.org>
Received: from mail-ed1-f70.google.com (mail-ed1-f70.google.com [209.85.208.70])
	by kanga.kvack.org (Postfix) with ESMTP id CA6FA8E0004
	for <linux-mm@kvack.org>; Fri,  7 Dec 2018 10:01:10 -0500 (EST)
Received: by mail-ed1-f70.google.com with SMTP id m19so2095594edc.6
        for <linux-mm@kvack.org>; Fri, 07 Dec 2018 07:01:10 -0800 (PST)
Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15])
        by mx.google.com with ESMTPS id n1si1073115edq.35.2018.12.07.07.01.09
        for <linux-mm@kvack.org>
        (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128);
        Fri, 07 Dec 2018 07:01:09 -0800 (PST)
Subject: Re: [PATCH v5 2/3] iommu/io-pgtable-arm-v7s: Request DMA32 memory,
 and improve debugging
References: <20181207061620.107881-1-drinkcat@chromium.org>
 <20181207061620.107881-3-drinkcat@chromium.org>
From: Vlastimil Babka <vbabka@suse.cz>
Message-ID: <78dfb949-ba3d-fd87-255e-65f142850b61@suse.cz>
Date: Fri, 7 Dec 2018 16:01:06 +0100
MIME-Version: 1.0
In-Reply-To: <20181207061620.107881-3-drinkcat@chromium.org>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Sender: owner-linux-mm@kvack.org
List-ID: <linux-mm.kvack.org>
To: Nicolas Boichat <drinkcat@chromium.org>, Will Deacon <will.deacon@arm.com>
Cc: Robin Murphy <robin.murphy@arm.com>, Joerg Roedel <joro@8bytes.org>, Christoph Lameter <cl@linux.com>, Pekka Enberg <penberg@kernel.org>, David Rientjes <rientjes@google.com>, Joonsoo Kim <iamjoonsoo.kim@lge.com>, Andrew Morton <akpm@linux-foundation.org>, Michal Hocko <mhocko@suse.com>, Mel Gorman <mgorman@techsingularity.net>, Levin Alexander <Alexander.Levin@microsoft.com>, Huaisheng Ye <yehs1@lenovo.com>, Mike Rapoport <rppt@linux.vnet.ibm.com>, linux-arm-kernel@lists.infradead.org, iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Yong Wu <yong.wu@mediatek.com>, Matthias Brugger <matthias.bgg@gmail.com>, Tomasz Figa <tfiga@google.com>, yingjoe.chen@mediatek.com, hch@infradead.org, Matthew Wilcox <willy@infradead.org>

On 12/7/18 7:16 AM, Nicolas Boichat wrote:
> IOMMUs using ARMv7 short-descriptor format require page tables
> (level 1 and 2) to be allocated within the first 4GB of RAM, even
> on 64-bit systems.
> 
> For level 1/2 pages, ensure GFP_DMA32 is used if CONFIG_ZONE_DMA32
> is defined (e.g. on arm64 platforms).
> 
> For level 2 pages, allocate a slab cache in SLAB_CACHE_DMA32. Note
> that we do not explicitly pass GFP_DMA[32] to kmem_cache_zalloc,
> as this is not strictly necessary, and would cause a warning
> in mm/sl*b.c, as we did not update GFP_SLAB_BUG_MASK.
> 
> Also, print an error when the physical address does not fit in
> 32-bit, to make debugging easier in the future.
> 
> Fixes: ad67f5a6545f ("arm64: replace ZONE_DMA with ZONE_DMA32")

Also, CC stable?

> Signed-off-by: Nicolas Boichat <drinkcat@chromium.org>