From mboxrd@z Thu Jan 1 00:00:00 1970 From: Robin Murphy Subject: Re: [PATCH 01/23] dma-mapping: provide a generic DMA_MAPPING_ERROR Date: Tue, 4 Dec 2018 16:41:34 +0000 Message-ID: <653ca801-63a1-3c19-ee09-ade19fa2bbb8@arm.com> References: <20181130132231.16512-1-hch@lst.de> <20181130132231.16512-2-hch@lst.de> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20181130132231.16512-2-hch@lst.de> Content-Language: en-GB Sender: linux-kernel-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: Christoph Hellwig , iommu@lists.linux-foundation.org Cc: linux-arch@vger.kernel.org, linux-alpha@vger.kernel.org, linux-ia64@vger.kernel.org, linux-parisc@vger.kernel.org, Linus Torvalds , x86@kernel.org, linux-kernel@vger.kernel.org, xen-devel@lists.xenproject.org, David Woodhouse , linux-arm-kernel@lists.infradead.org On 30/11/2018 13:22, Christoph Hellwig wrote: > Error handling of the dma_map_single and dma_map_page APIs is a little > problematic at the moment, in that we use different encodings in the > returned dma_addr_t to indicate an error. That means we require an > additional indirect call to figure out if a dma mapping call returned > an error, and a lot of boilerplate code to implement these semantics. > > Instead return the maximum addressable value as the error. As long > as we don't allow mapping single-byte ranges with single-byte alignment > this value can never be a valid return. Additionaly if drivers do > not check the return value from the dma_map* routines this values means > they will generally not be pointed to actual memory. > > Once the default value is added here we can start removing the > various mapping_error methods and just rely on this generic check. > > Signed-off-by: Christoph Hellwig > --- > include/linux/dma-mapping.h | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h > index 0f81c713f6e9..46bd612d929e 100644 > --- a/include/linux/dma-mapping.h > +++ b/include/linux/dma-mapping.h > @@ -133,6 +133,8 @@ struct dma_map_ops { > u64 (*get_required_mask)(struct device *dev); > }; > > +#define DMA_MAPPING_ERROR (~(dma_addr_t)0) > + > extern const struct dma_map_ops dma_direct_ops; > extern const struct dma_map_ops dma_virt_ops; > > @@ -576,6 +578,10 @@ static inline int dma_mapping_error(struct device *dev, dma_addr_t dma_addr) > const struct dma_map_ops *ops = get_dma_ops(dev); > > debug_dma_mapping_error(dev, dma_addr); > + > + if (dma_addr == DMA_MAPPING_ERROR) > + return 1; > + > if (ops->mapping_error) > return ops->mapping_error(dev, dma_addr); > return 0; I'd have been inclined to put the default check here, i.e. - return 0 + return dma_addr == DMA_MAPPING_ERROR such that the callback retains full precedence and we don't have to deal with the non-trivial removals immediately if it comes to it. Not that it makes a vast difference though, so either way, Reviewed-by: Robin Murphy From mboxrd@z Thu Jan 1 00:00:00 1970 From: Robin Murphy Date: Tue, 04 Dec 2018 16:41:34 +0000 Subject: Re: [PATCH 01/23] dma-mapping: provide a generic DMA_MAPPING_ERROR Message-Id: <653ca801-63a1-3c19-ee09-ade19fa2bbb8@arm.com> List-Id: References: <20181130132231.16512-1-hch@lst.de> <20181130132231.16512-2-hch@lst.de> In-Reply-To: <20181130132231.16512-2-hch@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Christoph Hellwig , iommu@lists.linux-foundation.org Cc: linux-arch@vger.kernel.org, linux-alpha@vger.kernel.org, linux-ia64@vger.kernel.org, linux-parisc@vger.kernel.org, Linus Torvalds , x86@kernel.org, linux-kernel@vger.kernel.org, xen-devel@lists.xenproject.org, David Woodhouse , linux-arm-kernel@lists.infradead.org On 30/11/2018 13:22, Christoph Hellwig wrote: > Error handling of the dma_map_single and dma_map_page APIs is a little > problematic at the moment, in that we use different encodings in the > returned dma_addr_t to indicate an error. That means we require an > additional indirect call to figure out if a dma mapping call returned > an error, and a lot of boilerplate code to implement these semantics. > > Instead return the maximum addressable value as the error. As long > as we don't allow mapping single-byte ranges with single-byte alignment > this value can never be a valid return. Additionaly if drivers do > not check the return value from the dma_map* routines this values means > they will generally not be pointed to actual memory. > > Once the default value is added here we can start removing the > various mapping_error methods and just rely on this generic check. > > Signed-off-by: Christoph Hellwig > --- > include/linux/dma-mapping.h | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h > index 0f81c713f6e9..46bd612d929e 100644 > --- a/include/linux/dma-mapping.h > +++ b/include/linux/dma-mapping.h > @@ -133,6 +133,8 @@ struct dma_map_ops { > u64 (*get_required_mask)(struct device *dev); > }; > > +#define DMA_MAPPING_ERROR (~(dma_addr_t)0) > + > extern const struct dma_map_ops dma_direct_ops; > extern const struct dma_map_ops dma_virt_ops; > > @@ -576,6 +578,10 @@ static inline int dma_mapping_error(struct device *dev, dma_addr_t dma_addr) > const struct dma_map_ops *ops = get_dma_ops(dev); > > debug_dma_mapping_error(dev, dma_addr); > + > + if (dma_addr = DMA_MAPPING_ERROR) > + return 1; > + > if (ops->mapping_error) > return ops->mapping_error(dev, dma_addr); > return 0; I'd have been inclined to put the default check here, i.e. - return 0 + return dma_addr = DMA_MAPPING_ERROR such that the callback retains full precedence and we don't have to deal with the non-trivial removals immediately if it comes to it. Not that it makes a vast difference though, so either way, Reviewed-by: Robin Murphy 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=-8.7 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED 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 861D7C04EBF for ; Tue, 4 Dec 2018 16:41:56 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 4CE5B206B7 for ; Tue, 4 Dec 2018 16:41:56 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="MP/ZOPEb" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4CE5B206B7 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender:Content-Type: Content-Transfer-Encoding:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Date:Message-ID:From: References:To:Subject:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=ru2CUfmd99go48ypVXvrMOlovRrTjMvrSqzyVpjKsyI=; b=MP/ZOPEb02D6yyEHHRRM5S2P9 OqOQnl5WxsWXEiX5tJjY8IkVdkqLDewq1+UI83B1L5HMSMZNBfUhfvjlXGThJuMDIO96hKV8ZmFjj vJunTIjdO9hh7Qfyxj2sTbswFxW9rbpaU/0e1TwNF94wWuOpzDFNEraF3OrFU4/vZLD3TRXJ68rqi mO2A2s2oREZOkNfYMcDEeyVs0VdrNnT3tm637mENJlpuVHztgoxYw7UKhugnqr2n+wIGBPNzPR3K0 hPpV/z4s7116V/8CkiskzXO0mYwyCSkfH16l86uAIdcsegz/SUSQDXZnwVsubg6dVG7VyOyvqNKJI pyjx7D60Q==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1gUDlh-0006VF-Q8; Tue, 04 Dec 2018 16:41:53 +0000 Received: from foss.arm.com ([217.140.101.70]) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1gUDle-0006I0-2j for linux-arm-kernel@lists.infradead.org; Tue, 04 Dec 2018 16:41:51 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id D4C8B15BE; Tue, 4 Dec 2018 08:41:37 -0800 (PST) Received: from [10.1.196.75] (e110467-lin.cambridge.arm.com [10.1.196.75]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id E1DA23F614; Tue, 4 Dec 2018 08:41:35 -0800 (PST) Subject: Re: [PATCH 01/23] dma-mapping: provide a generic DMA_MAPPING_ERROR To: Christoph Hellwig , iommu@lists.linux-foundation.org References: <20181130132231.16512-1-hch@lst.de> <20181130132231.16512-2-hch@lst.de> From: Robin Murphy Message-ID: <653ca801-63a1-3c19-ee09-ade19fa2bbb8@arm.com> Date: Tue, 4 Dec 2018 16:41:34 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.2.1 MIME-Version: 1.0 In-Reply-To: <20181130132231.16512-2-hch@lst.de> Content-Language: en-GB X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20181204_084150_130897_F6460A06 X-CRM114-Status: GOOD ( 25.52 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-arch@vger.kernel.org, linux-ia64@vger.kernel.org, linux-parisc@vger.kernel.org, David Woodhouse , x86@kernel.org, linux-kernel@vger.kernel.org, linux-alpha@vger.kernel.org, xen-devel@lists.xenproject.org, Linus Torvalds , linux-arm-kernel@lists.infradead.org Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 30/11/2018 13:22, Christoph Hellwig wrote: > Error handling of the dma_map_single and dma_map_page APIs is a little > problematic at the moment, in that we use different encodings in the > returned dma_addr_t to indicate an error. That means we require an > additional indirect call to figure out if a dma mapping call returned > an error, and a lot of boilerplate code to implement these semantics. > > Instead return the maximum addressable value as the error. As long > as we don't allow mapping single-byte ranges with single-byte alignment > this value can never be a valid return. Additionaly if drivers do > not check the return value from the dma_map* routines this values means > they will generally not be pointed to actual memory. > > Once the default value is added here we can start removing the > various mapping_error methods and just rely on this generic check. > > Signed-off-by: Christoph Hellwig > --- > include/linux/dma-mapping.h | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h > index 0f81c713f6e9..46bd612d929e 100644 > --- a/include/linux/dma-mapping.h > +++ b/include/linux/dma-mapping.h > @@ -133,6 +133,8 @@ struct dma_map_ops { > u64 (*get_required_mask)(struct device *dev); > }; > > +#define DMA_MAPPING_ERROR (~(dma_addr_t)0) > + > extern const struct dma_map_ops dma_direct_ops; > extern const struct dma_map_ops dma_virt_ops; > > @@ -576,6 +578,10 @@ static inline int dma_mapping_error(struct device *dev, dma_addr_t dma_addr) > const struct dma_map_ops *ops = get_dma_ops(dev); > > debug_dma_mapping_error(dev, dma_addr); > + > + if (dma_addr == DMA_MAPPING_ERROR) > + return 1; > + > if (ops->mapping_error) > return ops->mapping_error(dev, dma_addr); > return 0; I'd have been inclined to put the default check here, i.e. - return 0 + return dma_addr == DMA_MAPPING_ERROR such that the callback retains full precedence and we don't have to deal with the non-trivial removals immediately if it comes to it. Not that it makes a vast difference though, so either way, Reviewed-by: Robin Murphy _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel