Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755224AbaFLFwN (ORCPT ); Thu, 12 Jun 2014 01:52:13 -0400 Received: from LGEMRELSE6Q.lge.com ([156.147.1.121]:45207 "EHLO lgemrelse6q.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752549AbaFLFwK (ORCPT ); Thu, 12 Jun 2014 01:52:10 -0400 X-Original-SENDERIP: 10.177.220.169 X-Original-MAILFROM: minchan@kernel.org Date: Thu, 12 Jun 2014 14:52:20 +0900 From: Minchan Kim To: Joonsoo Kim Cc: Andrew Morton , "Aneesh Kumar K.V" , Marek Szyprowski , Michal Nazarewicz , Russell King - ARM Linux , kvm@vger.kernel.org, linux-mm@kvack.org, Gleb Natapov , Greg Kroah-Hartman , Alexander Graf , kvm-ppc@vger.kernel.org, linux-kernel@vger.kernel.org, Paul Mackerras , Benjamin Herrenschmidt , Paolo Bonzini , linuxppc-dev@lists.ozlabs.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v2 04/10] DMA, CMA: support alignment constraint on cma region Message-ID: <20140612055219.GG12415@bbox> References: <1402543307-29800-1-git-send-email-iamjoonsoo.kim@lge.com> <1402543307-29800-5-git-send-email-iamjoonsoo.kim@lge.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1402543307-29800-5-git-send-email-iamjoonsoo.kim@lge.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jun 12, 2014 at 12:21:41PM +0900, Joonsoo Kim wrote: > ppc kvm's cma area management needs alignment constraint on > cma region. So support it to prepare generalization of cma area > management functionality. > > Additionally, add some comments which tell us why alignment > constraint is needed on cma region. > > Signed-off-by: Joonsoo Kim > > diff --git a/drivers/base/dma-contiguous.c b/drivers/base/dma-contiguous.c > index 8a44c82..bc4c171 100644 > --- a/drivers/base/dma-contiguous.c > +++ b/drivers/base/dma-contiguous.c > @@ -32,6 +32,7 @@ > #include > #include > #include > +#include > > struct cma { > unsigned long base_pfn; > @@ -219,6 +220,7 @@ core_initcall(cma_init_reserved_areas); > * @size: Size of the reserved area (in bytes), > * @base: Base address of the reserved area optional, use 0 for any > * @limit: End address of the reserved memory (optional, 0 for any). > + * @alignment: Alignment for the contiguous memory area, should be power of 2 > * @res_cma: Pointer to store the created cma region. > * @fixed: hint about where to place the reserved area > * Pz, move the all description to new API function rather than internal one. > @@ -233,15 +235,15 @@ core_initcall(cma_init_reserved_areas); > */ > static int __init __dma_contiguous_reserve_area(phys_addr_t size, > phys_addr_t base, phys_addr_t limit, > + phys_addr_t alignment, > struct cma **res_cma, bool fixed) > { > struct cma *cma = &cma_areas[cma_area_count]; > - phys_addr_t alignment; > int ret = 0; > > - pr_debug("%s(size %lx, base %08lx, limit %08lx)\n", __func__, > - (unsigned long)size, (unsigned long)base, > - (unsigned long)limit); > + pr_debug("%s(size %lx, base %08lx, limit %08lx align_order %08lx)\n", Why is it called by "align_order"? > + __func__, (unsigned long)size, (unsigned long)base, > + (unsigned long)limit, (unsigned long)alignment); > > /* Sanity checks */ > if (cma_area_count == ARRAY_SIZE(cma_areas)) { > @@ -253,8 +255,17 @@ static int __init __dma_contiguous_reserve_area(phys_addr_t size, > if (!size) > return -EINVAL; > > - /* Sanitise input arguments */ > - alignment = PAGE_SIZE << max(MAX_ORDER - 1, pageblock_order); > + if (alignment && !is_power_of_2(alignment)) > + return -EINVAL; > + > + /* > + * Sanitise input arguments. > + * CMA area should be at least MAX_ORDER - 1 aligned. Otherwise, > + * CMA area could be merged into other MIGRATE_TYPE by buddy mechanism I'm not a native but try for clear documenation. Pages both ends in CMA area could be merged into adjacent unmovable migratetype page by page allocator's buddy algorithm. In the case, you couldn't get a contiguous memory, which is not what we want. > + * and CMA property will be broken. > + */ > + alignment = max(alignment, > + (phys_addr_t)PAGE_SIZE << max(MAX_ORDER - 1, pageblock_order)); > base = ALIGN(base, alignment); > size = ALIGN(size, alignment); > limit &= ~(alignment - 1); > @@ -302,7 +313,8 @@ int __init dma_contiguous_reserve_area(phys_addr_t size, phys_addr_t base, > { > int ret; > > - ret = __dma_contiguous_reserve_area(size, base, limit, res_cma, fixed); > + ret = __dma_contiguous_reserve_area(size, base, limit, 0, > + res_cma, fixed); > if (ret) > return ret; > > -- > 1.7.9.5 -- Kind regards, Minchan Kim -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/