Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758785AbaKUQbv (ORCPT ); Fri, 21 Nov 2014 11:31:51 -0500 Received: from smtp02.citrix.com ([66.165.176.63]:32819 "EHLO SMTP02.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750783AbaKUQbu (ORCPT ); Fri, 21 Nov 2014 11:31:50 -0500 X-IronPort-AV: E=Sophos;i="5.07,432,1413244800"; d="scan'208";a="195303813" Date: Fri, 21 Nov 2014 16:31:31 +0000 From: Stefano Stabellini X-X-Sender: sstabellini@kaball.uk.xensource.com To: Stefano Stabellini CC: , , Ian Campbell , , , , Catalin Marinas Subject: Re: [PATCH v9 10/13] xen/arm/arm64: introduce xen_arch_need_swiotlb In-Reply-To: <1415792454-23161-10-git-send-email-stefano.stabellini@eu.citrix.com> Message-ID: References: <1415792454-23161-10-git-send-email-stefano.stabellini@eu.citrix.com> User-Agent: Alpine 2.02 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" X-DLP: MIA2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 12 Nov 2014, Stefano Stabellini wrote: > Introduce an arch specific function to find out whether a particular dma > mapping operation needs to bounce on the swiotlb buffer. > > On ARM and ARM64, if the page involved is a foreign page and the device > is not coherent, we need to bounce because at unmap time we cannot > execute any required cache maintenance operations (we don't know how to > find the pfn from the mfn). > > No change of behaviour for x86. > > Signed-off-by: Stefano Stabellini > Reviewed-by: David Vrabel > Reviewed-by: Catalin Marinas > Acked-by: Ian Campbell > Acked-by: Konrad Rzeszutek Wilk I am thinking of asking a backport of this patch to 3.16+ The catch is that is_device_dma_coherent is not available on older kernels, so I'll have to change the arm implementation of xen_arch_need_swiotlb to: +bool xen_arch_need_swiotlb(struct device *dev, + unsigned long pfn, + unsigned long mfn) +{ + return pfn != mfn; +} + It is going to make things slower but it is going to fix the issue with cache flushing buffers for non-coherent devices. Konrad, are you OK with that? > Changes in v6: > - fix ts. > > Changes in v5: > - fix indentation. > --- > arch/arm/include/asm/xen/page.h | 4 ++++ > arch/arm/xen/mm.c | 7 +++++++ > arch/x86/include/asm/xen/page.h | 7 +++++++ > drivers/xen/swiotlb-xen.c | 5 ++++- > 4 files changed, 22 insertions(+), 1 deletion(-) > > diff --git a/arch/arm/include/asm/xen/page.h b/arch/arm/include/asm/xen/page.h > index 135c24a..68c739b 100644 > --- a/arch/arm/include/asm/xen/page.h > +++ b/arch/arm/include/asm/xen/page.h > @@ -107,4 +107,8 @@ static inline bool set_phys_to_machine(unsigned long pfn, unsigned long mfn) > #define xen_remap(cookie, size) ioremap_cache((cookie), (size)) > #define xen_unmap(cookie) iounmap((cookie)) > > +bool xen_arch_need_swiotlb(struct device *dev, > + unsigned long pfn, > + unsigned long mfn); > + > #endif /* _ASM_ARM_XEN_PAGE_H */ > diff --git a/arch/arm/xen/mm.c b/arch/arm/xen/mm.c > index ab700e1..28ebf3e 100644 > --- a/arch/arm/xen/mm.c > +++ b/arch/arm/xen/mm.c > @@ -100,6 +100,13 @@ void __xen_dma_sync_single_for_device(struct device *hwdev, > __xen_dma_page_cpu_to_dev(hwdev, handle, size, dir); > } > > +bool xen_arch_need_swiotlb(struct device *dev, > + unsigned long pfn, > + unsigned long mfn) > +{ > + return ((pfn != mfn) && !is_device_dma_coherent(dev)); > +} > + > int xen_create_contiguous_region(phys_addr_t pstart, unsigned int order, > unsigned int address_bits, > dma_addr_t *dma_handle) > diff --git a/arch/x86/include/asm/xen/page.h b/arch/x86/include/asm/xen/page.h > index c949923..f58ef6c 100644 > --- a/arch/x86/include/asm/xen/page.h > +++ b/arch/x86/include/asm/xen/page.h > @@ -236,4 +236,11 @@ void make_lowmem_page_readwrite(void *vaddr); > #define xen_remap(cookie, size) ioremap((cookie), (size)); > #define xen_unmap(cookie) iounmap((cookie)) > > +static inline bool xen_arch_need_swiotlb(struct device *dev, > + unsigned long pfn, > + unsigned long mfn) > +{ > + return false; > +} > + > #endif /* _ASM_X86_XEN_PAGE_H */ > diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c > index ad2c5eb..3725ee4 100644 > --- a/drivers/xen/swiotlb-xen.c > +++ b/drivers/xen/swiotlb-xen.c > @@ -399,7 +399,9 @@ dma_addr_t xen_swiotlb_map_page(struct device *dev, struct page *page, > * buffering it. > */ > if (dma_capable(dev, dev_addr, size) && > - !range_straddles_page_boundary(phys, size) && !swiotlb_force) { > + !range_straddles_page_boundary(phys, size) && > + !xen_arch_need_swiotlb(dev, PFN_DOWN(phys), PFN_DOWN(dev_addr)) && > + !swiotlb_force) { > /* we are not interested in the dma_addr returned by > * xen_dma_map_page, only in the potential cache flushes executed > * by the function. */ > @@ -557,6 +559,7 @@ xen_swiotlb_map_sg_attrs(struct device *hwdev, struct scatterlist *sgl, > dma_addr_t dev_addr = xen_phys_to_bus(paddr); > > if (swiotlb_force || > + xen_arch_need_swiotlb(hwdev, PFN_DOWN(paddr), PFN_DOWN(dev_addr)) || > !dma_capable(hwdev, dev_addr, sg->length) || > range_straddles_page_boundary(paddr, sg->length)) { > phys_addr_t map = swiotlb_tbl_map_single(hwdev, > -- > 1.7.10.4 > -- 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/