Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752641AbaKGOWR (ORCPT ); Fri, 7 Nov 2014 09:22:17 -0500 Received: from foss-mx-na.foss.arm.com ([217.140.108.86]:54609 "EHLO foss-mx-na.foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751960AbaKGOWQ (ORCPT ); Fri, 7 Nov 2014 09:22:16 -0500 Date: Fri, 7 Nov 2014 14:22:05 +0000 From: Catalin Marinas To: Stefano Stabellini Cc: "xen-devel@lists.xensource.com" , "Ian.Campbell@citrix.com" , "konrad.wilk@oracle.com" , "linux-kernel@vger.kernel.org" , "david.vrabel@citrix.com" , "linux-arm-kernel@lists.infradead.org" Subject: Re: [PATCH v7 6/8] xen/arm/arm64: merge xen/mm32.c into xen/mm.c Message-ID: <20141107142205.GD29148@e104818-lin.cambridge.arm.com> References: <1414422568-19103-6-git-send-email-stefano.stabellini@eu.citrix.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1414422568-19103-6-git-send-email-stefano.stabellini@eu.citrix.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Oct 27, 2014 at 03:09:26PM +0000, Stefano Stabellini wrote: > Merge xen/mm32.c into xen/mm.c. > As a consequence the code gets compiled on arm64 too: introduce a few > compat functions to actually be able to compile it. > > Signed-off-by: Stefano Stabellini > Acked-by: Ian Campbell Since I missed the commit introducing mm32.c (340720be32d4 xen/arm: reimplement xen_dma_unmap_page & friends), I'll add a retrospective NAK ;). The main reason is the asymmetry between dma map and unmap. With host swiotlb somehow getting !dma_capable(dev), you even risk leaking dom0 swiotlb bounce buffers (on arm64). > --- a/arch/arm/xen/mm.c > +++ b/arch/arm/xen/mm.c [...] > +/* functions called by SWIOTLB */ > + > +static void dma_cache_maint(dma_addr_t handle, unsigned long offset, > + size_t size, enum dma_data_direction dir, > + void (*op)(const void *, size_t, int)) > +{ > + unsigned long pfn; > + size_t left = size; > + > + pfn = (handle >> PAGE_SHIFT) + offset / PAGE_SIZE; > + offset %= PAGE_SIZE; > + > + do { > + size_t len = left; > + void *vaddr; > + > + if (!pfn_valid(pfn)) Is this the pfn or the mfn? As you said in the previous email, there is no mfn_to_pfn() conversion, so that's actually in another address space where dom0 pfn_valid() would not make sense. Do you use this as a check for foreign pages? If yes, is the mfn for such pages guaranteed to be different from any valid dom0 pfn? > + { > + /* TODO: cache flush */ What does this TODO mean here? Which cases are not covered yet? > + } else { > + struct page *page = pfn_to_page(pfn); If the pfn here is correct, can you not just have something like: void xen_dma_unmap_page(struct device *hwdev, dma_addr_t handle, size_t size, enum dma_data_direction dir, struct dma_attrs *attrs) { unsigned long pfn = handle >> PAGE_SHIFT; /* could use some macros */ if (!pfn_valid(pfn)) { /* FIXME */ return; } __generic_dma_ops(hwdev)->unmap_page(hwdev, handle, size, dir, attrs); } -- Catalin -- 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/