Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S264579AbUFXOhv (ORCPT ); Thu, 24 Jun 2004 10:37:51 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S264658AbUFXOhv (ORCPT ); Thu, 24 Jun 2004 10:37:51 -0400 Received: from cantor.suse.de ([195.135.220.2]:17128 "EHLO Cantor.suse.de") by vger.kernel.org with ESMTP id S264579AbUFXOhs (ORCPT ); Thu, 24 Jun 2004 10:37:48 -0400 Date: Thu, 24 Jun 2004 16:36:47 +0200 Message-ID: From: Takashi Iwai To: Andi Kleen Cc: Andi Kleen , Terence Ripperda , discuss@x86-64.org, linux-kernel@vger.kernel.org, andrea@suse.de Subject: Re: [discuss] Re: 32-bit dma allocations on 64-bit platforms In-Reply-To: <20040624112900.GE16727@wotan.suse.de> References: <20040623213643.GB32456@hygelac> <20040623234644.GC38425@colin2.muc.de> <20040624112900.GE16727@wotan.suse.de> User-Agent: Wanderlust/2.10.1 (Watching The Wheels) SEMI/1.14.5 (Awara-Onsen) FLIM/1.14.5 (Demachiyanagi) APEL/10.6 MULE XEmacs/21.4 (patch 15) (Security Through Obscurity) (i386-suse-linux) MIME-Version: 1.0 (generated by SEMI 1.14.5 - "Awara-Onsen") Content-Type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1888 Lines: 64 At Thu, 24 Jun 2004 13:29:00 +0200, Andi Kleen wrote: > > > Can't it be called with GFP_KERNEL at first, then with GFP_DMA if the > > allocated pages are out of dma mask, just like in pci-gart.c? > > (with ifdef x86-64) > > That won't work reliable enough in extreme cases. Well, it's not perfect, but it'd be far better than GFP_DMA only :) BTW, we have the similar problem on i386, too. The non-32bit DMA mask always results in the allocation with GFP_DMA. The patch below does similar hack as described above, calling with GFP_DMA as fallback. Takashi --- linux-2.6.7/arch/i386/kernel/pci-dma.c 2004-06-24 15:56:46.017473544 +0200 +++ linux-2.6.7/arch/i386/kernel/pci-dma.c 2004-06-24 16:05:02.449803937 +0200 @@ -17,17 +17,35 @@ void *dma_alloc_coherent(struct device * dma_addr_t *dma_handle, int gfp) { void *ret; + unsigned long dma_mask; + /* ignore region specifiers */ gfp &= ~(__GFP_DMA | __GFP_HIGHMEM); - if (dev == NULL || (dev->coherent_dma_mask < 0xffffffff)) + if (dev == NULL) { gfp |= GFP_DMA; + dma_mask = 0xffffffUL; + } else { + dma_mask = 0xffffffffUL; + if (dev->dma_mask) + dma_mask = *dev->dma_mask; + if (dev->coherent_dma_mask) + dma_mask &= (unsigned long)dev->coherent_dma_mask; + } + again: ret = (void *)__get_free_pages(gfp, get_order(size)); if (ret != NULL) { - memset(ret, 0, size); *dma_handle = virt_to_phys(ret); + if (((unsigned long)*dma_handle + size - 1) & ~dma_mask) { + free_pages((unsigned long)ret, get_order(size)); + if (gfp & GFP_DMA) + return NULL; + gfp |= GFP_DMA; + goto again; + } + memset(ret, 0, size); } return ret; } - 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/