From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2DCB1ECE587 for ; Mon, 14 Oct 2019 10:45:27 +0000 (UTC) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org [140.211.169.12]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 0E12F2168B for ; Mon, 14 Oct 2019 10:45:27 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0E12F2168B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=iommu-bounces@lists.linux-foundation.org Received: from mail.linux-foundation.org (localhost [127.0.0.1]) by mail.linuxfoundation.org (Postfix) with ESMTP id 09ADA28DB; Mon, 14 Oct 2019 10:45:19 +0000 (UTC) Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id 6A21428C1; Mon, 14 Oct 2019 10:29:29 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.7.6 X-Greylist: domain auto-whitelisted by SQLgrey-1.7.6 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp1.linuxfoundation.org (Postfix) with ESMTP id 8627E14D; Mon, 14 Oct 2019 10:29:28 +0000 (UTC) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id BDE68337; Mon, 14 Oct 2019 03:29:27 -0700 (PDT) Received: from [10.1.197.57] (e110467-lin.cambridge.arm.com [10.1.197.57]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 9C3363F718; Mon, 14 Oct 2019 03:29:25 -0700 (PDT) Subject: Re: [PATCH 1/2] dma-mapping: Add dma_addr_is_phys_addr() To: David Gibson , Ram Pai References: <1570843519-8696-1-git-send-email-linuxram@us.ibm.com> <1570843519-8696-2-git-send-email-linuxram@us.ibm.com> <20191014045139.GN4080@umbus.fritz.box> From: Robin Murphy Message-ID: <37609731-5539-b906-aa94-2ef0242795ac@arm.com> Date: Mon, 14 Oct 2019 11:29:24 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <20191014045139.GN4080@umbus.fritz.box> Content-Language: en-GB Cc: andmike@us.ibm.com, mdroth@linux.vnet.ibm.com, b.zolnierkie@samsung.com, mpe@ellerman.id.au, jasowang@redhat.com, aik@linux.ibm.com, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, paulus@ozlabs.org, iommu@lists.linux-foundation.org, paul.burton@mips.com, benh@kernel.crashing.org, sukadev@linux.vnet.ibm.com, linuxppc-dev@lists.ozlabs.org, hch@lst.de X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.12 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: iommu-bounces@lists.linux-foundation.org Errors-To: iommu-bounces@lists.linux-foundation.org On 14/10/2019 05:51, David Gibson wrote: > On Fri, Oct 11, 2019 at 06:25:18PM -0700, Ram Pai wrote: >> From: Thiago Jung Bauermann >> >> In order to safely use the DMA API, virtio needs to know whether DMA >> addresses are in fact physical addresses and for that purpose, >> dma_addr_is_phys_addr() is introduced. >> >> cc: Benjamin Herrenschmidt >> cc: David Gibson >> cc: Michael Ellerman >> cc: Paul Mackerras >> cc: Michael Roth >> cc: Alexey Kardashevskiy >> cc: Paul Burton >> cc: Robin Murphy >> cc: Bartlomiej Zolnierkiewicz >> cc: Marek Szyprowski >> cc: Christoph Hellwig >> Suggested-by: Michael S. Tsirkin >> Signed-off-by: Ram Pai >> Signed-off-by: Thiago Jung Bauermann > > The change itself looks ok, so > > Reviewed-by: David Gibson > > However, I would like to see the commit message (and maybe the inline > comments) expanded a bit on what the distinction here is about. Some > of the text from the next patch would be suitable, about DMA addresses > usually being in a different address space but not in the case of > bounce buffering. Right, this needs a much tighter definition. "DMA address happens to be a valid physical address" is true of various IOMMU setups too, but I can't believe it's meaningful in such cases. If what you actually want is "DMA is direct or SWIOTLB" - i.e. "DMA address is physical address of DMA data (not necessarily the original buffer)" - wouldn't dma_is_direct() suffice? Robin. >> --- >> arch/powerpc/include/asm/dma-mapping.h | 21 +++++++++++++++++++++ >> arch/powerpc/platforms/pseries/Kconfig | 1 + >> include/linux/dma-mapping.h | 20 ++++++++++++++++++++ >> kernel/dma/Kconfig | 3 +++ >> 4 files changed, 45 insertions(+) >> >> diff --git a/arch/powerpc/include/asm/dma-mapping.h b/arch/powerpc/include/asm/dma-mapping.h >> index 565d6f7..f92c0a4b 100644 >> --- a/arch/powerpc/include/asm/dma-mapping.h >> +++ b/arch/powerpc/include/asm/dma-mapping.h >> @@ -5,6 +5,8 @@ >> #ifndef _ASM_DMA_MAPPING_H >> #define _ASM_DMA_MAPPING_H >> >> +#include >> + >> static inline const struct dma_map_ops *get_arch_dma_ops(struct bus_type *bus) >> { >> /* We don't handle the NULL dev case for ISA for now. We could >> @@ -15,4 +17,23 @@ static inline const struct dma_map_ops *get_arch_dma_ops(struct bus_type *bus) >> return NULL; >> } >> >> +#ifdef CONFIG_ARCH_HAS_DMA_ADDR_IS_PHYS_ADDR >> +/** >> + * dma_addr_is_phys_addr - check whether a device DMA address is a physical >> + * address >> + * @dev: device to check >> + * >> + * Returns %true if any DMA address for this device happens to also be a valid >> + * physical address (not necessarily of the same page). >> + */ >> +static inline bool dma_addr_is_phys_addr(struct device *dev) >> +{ >> + /* >> + * Secure guests always use the SWIOTLB, therefore DMA addresses are >> + * actually the physical address of the bounce buffer. >> + */ >> + return is_secure_guest(); >> +} >> +#endif >> + >> #endif /* _ASM_DMA_MAPPING_H */ >> diff --git a/arch/powerpc/platforms/pseries/Kconfig b/arch/powerpc/platforms/pseries/Kconfig >> index 9e35cdd..0108150 100644 >> --- a/arch/powerpc/platforms/pseries/Kconfig >> +++ b/arch/powerpc/platforms/pseries/Kconfig >> @@ -152,6 +152,7 @@ config PPC_SVM >> select SWIOTLB >> select ARCH_HAS_MEM_ENCRYPT >> select ARCH_HAS_FORCE_DMA_UNENCRYPTED >> + select ARCH_HAS_DMA_ADDR_IS_PHYS_ADDR >> help >> There are certain POWER platforms which support secure guests using >> the Protected Execution Facility, with the help of an Ultravisor >> diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h >> index f7d1eea..6df5664 100644 >> --- a/include/linux/dma-mapping.h >> +++ b/include/linux/dma-mapping.h >> @@ -693,6 +693,26 @@ static inline bool dma_addressing_limited(struct device *dev) >> dma_get_required_mask(dev); >> } >> >> +#ifndef CONFIG_ARCH_HAS_DMA_ADDR_IS_PHYS_ADDR >> +/** >> + * dma_addr_is_phys_addr - check whether a device DMA address is a physical >> + * address >> + * @dev: device to check >> + * >> + * Returns %true if any DMA address for this device happens to also be a valid >> + * physical address (not necessarily of the same page). >> + */ >> +static inline bool dma_addr_is_phys_addr(struct device *dev) >> +{ >> + /* >> + * Except in very specific setups, DMA addresses exist in a different >> + * address space from CPU physical addresses and cannot be directly used >> + * to reference system memory. >> + */ >> + return false; >> +} >> +#endif >> + >> #ifdef CONFIG_ARCH_HAS_SETUP_DMA_OPS >> void arch_setup_dma_ops(struct device *dev, u64 dma_base, u64 size, >> const struct iommu_ops *iommu, bool coherent); >> diff --git a/kernel/dma/Kconfig b/kernel/dma/Kconfig >> index 9decbba..6209b46 100644 >> --- a/kernel/dma/Kconfig >> +++ b/kernel/dma/Kconfig >> @@ -51,6 +51,9 @@ config ARCH_HAS_DMA_MMAP_PGPROT >> config ARCH_HAS_FORCE_DMA_UNENCRYPTED >> bool >> >> +config ARCH_HAS_DMA_ADDR_IS_PHYS_ADDR >> + bool >> + >> config DMA_NONCOHERENT_CACHE_SYNC >> bool >> > _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu