Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751446AbdGZJ1D (ORCPT ); Wed, 26 Jul 2017 05:27:03 -0400 Received: from mail-yw0-f172.google.com ([209.85.161.172]:34556 "EHLO mail-yw0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750816AbdGZJ1B (ORCPT ); Wed, 26 Jul 2017 05:27:01 -0400 MIME-Version: 1.0 In-Reply-To: <20170726091545.GC15833@8bytes.org> References: <20170704135556.21704-1-tfiga@chromium.org> <20170726091545.GC15833@8bytes.org> From: Tomasz Figa Date: Wed, 26 Jul 2017 18:26:39 +0900 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v2 1/2] iommu/dma: Respect __GFP_DMA and __GFP_DMA32 in incoming GFP flags To: Joerg Roedel Cc: "open list:IOMMU DRIVERS" , "linux-kernel@vger.kernel.org" , Robin Murphy Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1106 Lines: 29 Hi Joerg, On Wed, Jul 26, 2017 at 6:15 PM, Joerg Roedel wrote: > On Tue, Jul 04, 2017 at 10:55:55PM +0900, Tomasz Figa wrote: >> Current implementation of __iommu_dma_alloc_pages() keeps adding >> __GFP_HIGHMEM to GFP flags regardless of whether other zone flags are >> already included in the incoming flags. If __GFP_DMA or __GFP_DMA32 is >> set at the same time as __GFP_HIGHMEM, the allocation fails due to >> invalid zone flag combination. >> >> Fix this by checking for __GFP_DMA and __GFP_DMA32 in incoming GFP flags >> and adding __GFP_HIGHMEM only if they are not present. >> >> Signed-off-by: Tomasz Figa > > Isn't it better to mask out __GFP_DMA and __GFP_DMA32 in the allocation > flags and only take them into account for iova allocation? > > When the IOMMU re-maps the DMA to this memory it doesn't matter where it > is in system memory. It's a platform specific knowledge and I'd say the generic helper is not where it should be decided. Please see my reply to Robin for v1 [1]. [1] https://patchwork.kernel.org/patch/9810921/ Best regards. Tomasz