From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <akpm@linux-foundation.org>
Received: from mail.linuxfoundation.org (mail.linuxfoundation.org
 [140.211.169.12])
 by lists.ozlabs.org (Postfix) with ESMTP id B9DAF1A02E7
 for <linuxppc-dev@lists.ozlabs.org>; Thu, 19 Jun 2014 06:48:18 +1000 (EST)
Date: Wed, 18 Jun 2014 13:48:15 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Subject: Re: [PATCH v3 -next 4/9] DMA, CMA: support arbitrary bitmap
 granularity
Message-Id: <20140618134815.69c4d0a5f916846f9857e9ff@linux-foundation.org>
In-Reply-To: <1402897251-23639-5-git-send-email-iamjoonsoo.kim@lge.com>
References: <1402897251-23639-1-git-send-email-iamjoonsoo.kim@lge.com>
 <1402897251-23639-5-git-send-email-iamjoonsoo.kim@lge.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Cc: kvm-ppc@vger.kernel.org, Russell King - ARM Linux <linux@arm.linux.org.uk>,
 kvm@vger.kernel.org, linux-mm@kvack.org, Gleb Natapov <gleb@kernel.org>,
 Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
 Alexander Graf <agraf@suse.de>, Michal Nazarewicz <mina86@mina86.com>,
 linux-kernel@vger.kernel.org, Minchan Kim <minchan@kernel.org>,
 Paul Mackerras <paulus@samba.org>,
 "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>,
 Paolo Bonzini <pbonzini@redhat.com>, Zhang Yanfei <zhangyanfei@cn.fujitsu.com>,
 linuxppc-dev@lists.ozlabs.org, linux-arm-kernel@lists.infradead.org,
 Marek Szyprowski <m.szyprowski@samsung.com>
List-Id: Linux on PowerPC Developers Mail List <linuxppc-dev.lists.ozlabs.org>
List-Unsubscribe: <https://lists.ozlabs.org/options/linuxppc-dev>,
 <mailto:linuxppc-dev-request@lists.ozlabs.org?subject=unsubscribe>
List-Archive: <http://lists.ozlabs.org/pipermail/linuxppc-dev/>
List-Post: <mailto:linuxppc-dev@lists.ozlabs.org>
List-Help: <mailto:linuxppc-dev-request@lists.ozlabs.org?subject=help>
List-Subscribe: <https://lists.ozlabs.org/listinfo/linuxppc-dev>,
 <mailto:linuxppc-dev-request@lists.ozlabs.org?subject=subscribe>

On Mon, 16 Jun 2014 14:40:46 +0900 Joonsoo Kim <iamjoonsoo.kim@lge.com> wrote:

> PPC KVM's CMA area management requires arbitrary bitmap granularity,
> since they want to reserve very large memory and manage this region
> with bitmap that one bit for several pages to reduce management overheads.
> So support arbitrary bitmap granularity for following generalization.
> 
> ...
>
> --- a/drivers/base/dma-contiguous.c
> +++ b/drivers/base/dma-contiguous.c
> @@ -38,6 +38,7 @@ struct cma {
>  	unsigned long	base_pfn;
>  	unsigned long	count;
>  	unsigned long	*bitmap;
> +	unsigned int order_per_bit; /* Order of pages represented by one bit */
>  	struct mutex	lock;
>  };
>  
> @@ -157,9 +158,37 @@ void __init dma_contiguous_reserve(phys_addr_t limit)
>  
>  static DEFINE_MUTEX(cma_mutex);
>  
> +static unsigned long cma_bitmap_aligned_mask(struct cma *cma, int align_order)
> +{
> +	return (1 << (align_order >> cma->order_per_bit)) - 1;
> +}

Might want a "1UL << ..." here.

> +static unsigned long cma_bitmap_maxno(struct cma *cma)
> +{
> +	return cma->count >> cma->order_per_bit;
> +}
> +
> +static unsigned long cma_bitmap_pages_to_bits(struct cma *cma,
> +						unsigned long pages)
> +{
> +	return ALIGN(pages, 1 << cma->order_per_bit) >> cma->order_per_bit;
> +}

Ditto.  I'm not really sure what the compiler will do in these cases,
but would prefer not to rely on it anyway!


--- a/drivers/base/dma-contiguous.c~dma-cma-support-arbitrary-bitmap-granularity-fix
+++ a/drivers/base/dma-contiguous.c
@@ -160,7 +160,7 @@ static DEFINE_MUTEX(cma_mutex);
 
 static unsigned long cma_bitmap_aligned_mask(struct cma *cma, int align_order)
 {
-	return (1 << (align_order >> cma->order_per_bit)) - 1;
+	return (1UL << (align_order >> cma->order_per_bit)) - 1;
 }
 
 static unsigned long cma_bitmap_maxno(struct cma *cma)
@@ -171,7 +171,7 @@ static unsigned long cma_bitmap_maxno(st
 static unsigned long cma_bitmap_pages_to_bits(struct cma *cma,
 						unsigned long pages)
 {
-	return ALIGN(pages, 1 << cma->order_per_bit) >> cma->order_per_bit;
+	return ALIGN(pages, 1UL << cma->order_per_bit) >> cma->order_per_bit;
 }
 
 static void cma_clear_bitmap(struct cma *cma, unsigned long pfn, int count)
_