From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753286AbYIXM57 (ORCPT ); Wed, 24 Sep 2008 08:57:59 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751538AbYIXM5v (ORCPT ); Wed, 24 Sep 2008 08:57:51 -0400 Received: from outbound-wa4.frontbridge.com ([216.32.181.16]:54466 "EHLO WA4EHSOBE002.bigfish.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751456AbYIXM5u (ORCPT ); Wed, 24 Sep 2008 08:57:50 -0400 X-BigFish: VPS-37(zz1418M1432R98dR1805M179dR936fO873fnzzzz2f39iz32i6bh43j61h) X-Spam-TCS-SCL: 0:0 X-FB-SS: 5, X-WSS-ID: 0K7PAO2-03-LI0-01 Date: Wed, 24 Sep 2008 14:57:40 +0200 From: Joerg Roedel To: FUJITA Tomonori CC: mingo@elte.hu, linux-kernel@vger.kernel.org, andi@firstfloor.org Subject: Re: [PATCH 3/3] x86: restore old GART alloc_coherent behavior Message-ID: <20080924125740.GT24392@amd.com> References: <1222256917-14321-3-git-send-email-fujita.tomonori@lab.ntt.co.jp> <1222256917-14321-4-git-send-email-fujita.tomonori@lab.ntt.co.jp> <20080924121127.GS24392@amd.com> <20080924214353U.fujita.tomonori@lab.ntt.co.jp> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20080924214353U.fujita.tomonori@lab.ntt.co.jp> User-Agent: mutt-ng/devel-r804 (Linux) X-OriginalArrivalTime: 24 Sep 2008 12:57:40.0800 (UTC) FILETIME=[20C30C00:01C91E45] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Sep 24, 2008 at 09:43:59PM +0900, FUJITA Tomonori wrote: > On Wed, 24 Sep 2008 14:11:27 +0200 > Joerg Roedel wrote: > > > On Wed, Sep 24, 2008 at 08:48:37PM +0900, FUJITA Tomonori wrote: > > > Currently, GART alloc_coherent tries to allocate pages with GFP_DMA32 > > > for a device having dma_masks > 24bit < 32bits. If GART gets an > > > address that a device can't access to, GART try to map the address to > > > a virtual I/O address that the device can access to. > > > > > > But Andi pointed out, "The GART is somewhere in the 4GB range so you > > > cannot use it to map anything < 4GB. Also GART is pretty small." > > > > > > http://lkml.org/lkml/2008/9/12/43 > > > > > > That is, it's possible that GART doesn't have virtual I/O address > > > space that a device can access to. The above behavior doesn't work for > > > a device having dma_masks > 24bit < 32bits. > > > > > > This patch restores old GART alloc_coherent behavior (before the > > > alloc_coherent rewrite). > > > > Patchset looks good in principle. But I have a small question, see > > below. > > > > > > > > Signed-off-by: FUJITA Tomonori > > > --- > > > arch/x86/kernel/pci-gart_64.c | 43 +++++++++++++++++++--------------------- > > > 1 files changed, 20 insertions(+), 23 deletions(-) > > > > > > diff --git a/arch/x86/kernel/pci-gart_64.c b/arch/x86/kernel/pci-gart_64.c > > > index 7e08e46..25c94fb 100644 > > > --- a/arch/x86/kernel/pci-gart_64.c > > > +++ b/arch/x86/kernel/pci-gart_64.c > > > @@ -487,31 +487,28 @@ static void * > > > gart_alloc_coherent(struct device *dev, size_t size, dma_addr_t *dma_addr, > > > gfp_t flag) > > > { > > > - void *vaddr; > > > dma_addr_t paddr; > > > unsigned long align_mask; > > > - u64 dma_mask = dma_alloc_coherent_mask(dev, flag); > > > - > > > - vaddr = (void *)__get_free_pages(flag | __GFP_ZERO, get_order(size)); > > > - if (!vaddr) > > > - return NULL; > > > - > > > - paddr = virt_to_phys(vaddr); > > > - if (is_buffer_dma_capable(dma_mask, paddr, size)) { > > > - *dma_addr = paddr; > > > - return vaddr; > > > - } > > > - > > > - align_mask = (1UL << get_order(size)) - 1; > > > - > > > - *dma_addr = dma_map_area(dev, paddr, size, DMA_BIDIRECTIONAL, > > > - align_mask); > > > - flush_gart(); > > > - > > > - if (*dma_addr != bad_dma_address) > > > - return vaddr; > > > - > > > - free_pages((unsigned long)vaddr, get_order(size)); > > > + struct page *page; > > > + > > > + if (force_iommu && !(flag & GFP_DMA)) { > > > + flag &= ~(__GFP_DMA | __GFP_HIGHMEM | __GFP_DMA32); > > > + page = alloc_pages(flag | __GFP_ZERO, get_order(size)); > > > + if (!page) > > > + return NULL; > > > + > > > + align_mask = (1UL << get_order(size)) - 1; > > > + paddr = dma_map_area(dev, page_to_phys(page), size, > > > + DMA_BIDIRECTIONAL, align_mask); > > > > Can't we check if a mapping is required before calling dma_map_area? > > Your recently introduced IOMMU helper functions should make that easy > > and GART address space is a rare resource. AFAIR this is also the > > behaviour of the old generic dma_alloc_coherent function. > > I think that the behavior of the old generic dma_alloc_coherent > function and GART is different. > > The old GART code does virtual mappings only with force_iommu option > enabled. The old GART code always do virtual mappings with force_iommu > option enabled (unless GFP_DMA is set). Hmm true, the old code called map_simple and not map_single so it mapped always. > > > > > + > > > + flush_gart(); > > > > This should depend on need_flush. > > Theoretically, yes, I think. But this patch restores the old GART code > behavior. Ok. The map_simple function of GART did it unconditionally too so this is the old behavior. But its safe here to flush conditionally. I'll send a follow-up patch. Joerg -- | AMD Saxony Limited Liability Company & Co. 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