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 X-Spam-Level: X-Spam-Status: No, score=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id ACE52C43441 for ; Fri, 9 Nov 2018 10:43:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 69FFC20892 for ; Fri, 9 Nov 2018 10:43:31 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 69FFC20892 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.cz Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728219AbeKIUXa (ORCPT ); Fri, 9 Nov 2018 15:23:30 -0500 Received: from mx2.suse.de ([195.135.220.15]:58164 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727560AbeKIUXa (ORCPT ); Fri, 9 Nov 2018 15:23:30 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay1.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 4F1BAAF58; Fri, 9 Nov 2018 10:43:26 +0000 (UTC) Subject: Re: [PATCH RFC 1/3] mm: When CONFIG_ZONE_DMA32 is set, use DMA32 for SLAB_CACHE_DMA To: Nicolas Boichat , Robin Murphy Cc: Will Deacon , Joerg Roedel , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton , Michal Hocko , Mel Gorman , Levin Alexander , Huaisheng Ye , Mike Rapoport , linux-arm-kernel@lists.infradead.org, iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Yong Wu , Matthias Brugger , Tomasz Figa , yingjoe.chen@mediatek.com References: <20181109082448.150302-1-drinkcat@chromium.org> <20181109082448.150302-2-drinkcat@chromium.org> From: Vlastimil Babka Openpgp: preference=signencrypt Autocrypt: addr=vbabka@suse.cz; 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Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.2.1 MIME-Version: 1.0 In-Reply-To: <20181109082448.150302-2-drinkcat@chromium.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/9/18 9:24 AM, Nicolas Boichat wrote: > Some callers, namely iommu/io-pgtable-arm-v7s, expect the physical > address returned by kmem_cache_alloc with GFP_DMA parameter to be > a 32-bit address. > > Instead of adding a separate SLAB_CACHE_DMA32 (and then audit > all the calls to check if they require memory from DMA or DMA32 > zone), we simply allocate SLAB_CACHE_DMA cache in DMA32 region, > if CONFIG_ZONE_DMA32 is set. > > Fixes: ad67f5a6545f ("arm64: replace ZONE_DMA with ZONE_DMA32") > Signed-off-by: Nicolas Boichat > --- > include/linux/slab.h | 13 ++++++++++++- > mm/slab.c | 2 +- > mm/slub.c | 2 +- > 3 files changed, 14 insertions(+), 3 deletions(-) > > diff --git a/include/linux/slab.h b/include/linux/slab.h > index 918f374e7156f4..390afe90c5dec0 100644 > --- a/include/linux/slab.h > +++ b/include/linux/slab.h > @@ -30,7 +30,7 @@ > #define SLAB_POISON ((slab_flags_t __force)0x00000800U) > /* Align objs on cache lines */ > #define SLAB_HWCACHE_ALIGN ((slab_flags_t __force)0x00002000U) > -/* Use GFP_DMA memory */ > +/* Use GFP_DMA or GFP_DMA32 memory */ > #define SLAB_CACHE_DMA ((slab_flags_t __force)0x00004000U) > /* DEBUG: Store the last owner for bug hunting */ > #define SLAB_STORE_USER ((slab_flags_t __force)0x00010000U) > @@ -126,6 +126,17 @@ > #define ZERO_OR_NULL_PTR(x) ((unsigned long)(x) <= \ > (unsigned long)ZERO_SIZE_PTR) > > +/* > + * When ZONE_DMA32 is defined, have SLAB_CACHE_DMA allocate memory with > + * GFP_DMA32 instead of GFP_DMA, as this is what some of the callers > + * require (instead of duplicating cache for DMA and DMA32 zones). > + */ > +#ifdef CONFIG_ZONE_DMA32 > +#define SLAB_CACHE_DMA_GFP GFP_DMA32 > +#else > +#define SLAB_CACHE_DMA_GFP GFP_DMA > +#endif AFAICS this will break e.g. x86 which can have both ZONE_DMA and ZONE_DMA32, and now you would make kmalloc(__GFP_DMA) return objects from ZONE_DMA32 instead of __ZONE_DMA, which can break something. Also I'm probably missing the point of this all. In patch 3 you use __get_dma32_pages() thus __get_free_pages(__GFP_DMA32), which uses alloc_pages, thus the page allocator directly, and there's no slab caches involved. It makes little sense to involve slab for page table allocations anyway, as those tend to be aligned to a page size (or high-order page size). So what am I missing?