Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755028AbbDTMCs (ORCPT ); Mon, 20 Apr 2015 08:02:48 -0400 Received: from smtp02.citrix.com ([66.165.176.63]:32623 "EHLO SMTP02.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754600AbbDTMCq (ORCPT ); Mon, 20 Apr 2015 08:02:46 -0400 X-IronPort-AV: E=Sophos;i="5.11,609,1422921600"; d="scan'208";a="256616561" Message-ID: <5534EAE3.8060403@citrix.com> Date: Mon, 20 Apr 2015 13:02:43 +0100 From: David Vrabel User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Icedove/31.4.0 MIME-Version: 1.0 To: Chen Baozi , David Vrabel CC: , , , Subject: Re: [Xen-devel] [PATCH] xen: Add __GFP_DMA flag when xen_swiotlb_init gets free pages. References: <1429526904-27176-1-git-send-email-cbz@baozis.org> <5534DABB.5060305@citrix.com> <20150420110729.GA27707@cbz-thinkpad> In-Reply-To: <20150420110729.GA27707@cbz-thinkpad> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit X-DLP: MIA2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1627 Lines: 42 On 20/04/15 12:07, Chen Baozi wrote: > On Mon, Apr 20, 2015 at 11:53:47AM +0100, David Vrabel wrote: >> On 20/04/15 11:48, Chen Baozi wrote: >>> Make sure that xen_swiotlb_init allocates buffers that is DMA capable. >>> >>> Signed-off-by: Chen Baozi >>> --- >>> drivers/xen/swiotlb-xen.c | 3 ++- >>> 1 file changed, 2 insertions(+), 1 deletion(-) >>> >>> diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c >>> index 810ad41..7345afd 100644 >>> --- a/drivers/xen/swiotlb-xen.c >>> +++ b/drivers/xen/swiotlb-xen.c >>> @@ -235,7 +235,8 @@ retry: >>> #define SLABS_PER_PAGE (1 << (PAGE_SHIFT - IO_TLB_SHIFT)) >>> #define IO_TLB_MIN_SLABS ((1<<20) >> IO_TLB_SHIFT) >>> while ((SLABS_PER_PAGE << order) > IO_TLB_MIN_SLABS) { >>> - xen_io_tlb_start = (void *)__get_free_pages(__GFP_NOWARN, order); >>> + xen_io_tlb_start = (void *)__get_free_pages( >>> + __GFP_NOWARN|__GFP_DMA, order); >> >> I think this breaks x86 where __GFP_DMA means below 16 MB. Perhaps you >> mean __GFP_DMA32? > > __GFP_DMA32 doesn't help on arm64... > > I guess there might be conflicts about the meaning of __GFP_DMA between x86 and > arm? Yes. This is also conceptually wrong since it doesn't matter where the pages are in PFN space, but where they are in bus address (MFN) space (which is what the subsequent hypercall is required to sort out). David -- 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/