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Mon, 3 May 2021 00:32:04 +0000 Received: from [10.2.50.162] (172.20.145.6) by HQMAIL107.nvidia.com (172.20.187.13) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Mon, 3 May 2021 00:32:02 +0000 Subject: Re: [PATCH 10/16] dma-mapping: Add flags to dma_map_ops to indicate PCI P2PDMA support To: Logan Gunthorpe , , , , , , CC: Stephen Bates , Christoph Hellwig , Dan Williams , Jason Gunthorpe , =?UTF-8?Q?Christian_K=c3=b6nig?= , Don Dutile , Matthew Wilcox , Daniel Vetter , Jakowski Andrzej , Minturn Dave B , Jason Ekstrand , Dave Hansen , Xiong Jianxin , Bjorn Helgaas , Ira Weiny , Robin Murphy References: <20210408170123.8788-1-logang@deltatee.com> <20210408170123.8788-11-logang@deltatee.com> From: John Hubbard Message-ID: <85bd104b-2816-f803-44d4-d5623d4f81af@nvidia.com> Date: Sun, 2 May 2021 17:32:02 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.10.0 MIME-Version: 1.0 In-Reply-To: <20210408170123.8788-11-logang@deltatee.com> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [172.20.145.6] X-ClientProxiedBy: HQMAIL111.nvidia.com (172.20.187.18) To HQMAIL107.nvidia.com (172.20.187.13) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 82c61071-4fbe-4bb0-1a41-08d90dcae049 X-MS-TrafficTypeDiagnostic: MN2PR12MB3232: X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:3968; X-MS-Exchange-SenderADCheck: 1 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:216.228.112.34;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:mail.nvidia.com;PTR:schybrid03.nvidia.com;CAT:NONE;SFS:(4636009)(136003)(376002)(39860400002)(346002)(396003)(46966006)(36840700001)(7636003)(426003)(2906002)(7416002)(316002)(47076005)(83380400001)(26005)(110136005)(86362001)(336012)(31696002)(8936002)(5660300002)(82310400003)(8676002)(70206006)(53546011)(82740400003)(36756003)(70586007)(186003)(16526019)(478600001)(31686004)(36906005)(356005)(2616005)(54906003)(16576012)(36860700001)(4326008)(43740500002)(2101003);DIR:OUT;SFP:1101; X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 03 May 2021 00:32:04.5866 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 82c61071-4fbe-4bb0-1a41-08d90dcae049 X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.112.34];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: DM6NAM11FT031.eop-nam11.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: MN2PR12MB3232 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 4/8/21 10:01 AM, Logan Gunthorpe wrote: > Add a flags member to the dma_map_ops structure with one flag to > indicate support for PCI P2PDMA. > > Also, add a helper to check if a device supports PCI P2PDMA. > > Signed-off-by: Logan Gunthorpe > --- > include/linux/dma-map-ops.h | 3 +++ > include/linux/dma-mapping.h | 5 +++++ > kernel/dma/mapping.c | 18 ++++++++++++++++++ > 3 files changed, 26 insertions(+) > > diff --git a/include/linux/dma-map-ops.h b/include/linux/dma-map-ops.h > index 51872e736e7b..481892822104 100644 > --- a/include/linux/dma-map-ops.h > +++ b/include/linux/dma-map-ops.h > @@ -12,6 +12,9 @@ > struct cma; > > struct dma_map_ops { > + unsigned int flags; > +#define DMA_F_PCI_P2PDMA_SUPPORTED (1 << 0) > + Can we move this up and out of the struct member area, so that it looks more like this: /* * Values for struct dma_map_ops.flags: * * DMA_F_PCI_P2PDMA_SUPPORTED: */ #define DMA_F_PCI_P2PDMA_SUPPORTED (1 << 0) struct dma_map_ops { unsigned int flags; > void *(*alloc)(struct device *dev, size_t size, > dma_addr_t *dma_handle, gfp_t gfp, > unsigned long attrs); > diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h > index 50b8f586cf59..c31980ecca62 100644 > --- a/include/linux/dma-mapping.h > +++ b/include/linux/dma-mapping.h > @@ -146,6 +146,7 @@ int dma_mmap_attrs(struct device *dev, struct vm_area_struct *vma, > unsigned long attrs); > bool dma_can_mmap(struct device *dev); > int dma_supported(struct device *dev, u64 mask); > +bool dma_pci_p2pdma_supported(struct device *dev); > int dma_set_mask(struct device *dev, u64 mask); > int dma_set_coherent_mask(struct device *dev, u64 mask); > u64 dma_get_required_mask(struct device *dev); > @@ -247,6 +248,10 @@ static inline int dma_supported(struct device *dev, u64 mask) > { > return 0; > } > +static inline bool dma_pci_p2pdma_supported(struct device *dev) > +{ > + return 0; Should be: return false; > +} > static inline int dma_set_mask(struct device *dev, u64 mask) > { > return -EIO; > diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c > index 923089c4267b..ce44a0fcc4e5 100644 > --- a/kernel/dma/mapping.c > +++ b/kernel/dma/mapping.c > @@ -573,6 +573,24 @@ int dma_supported(struct device *dev, u64 mask) > } > EXPORT_SYMBOL(dma_supported); > > +bool dma_pci_p2pdma_supported(struct device *dev) > +{ > + const struct dma_map_ops *ops = get_dma_ops(dev); > + > + /* if ops is not set, dma direct will be used which supports P2PDMA */ > + if (!ops) > + return true; > + > + /* > + * Note: dma_ops_bypass is not checked here because P2PDMA should > + * not be used with dma mapping ops that do not have support even > + * if the specific device is bypassing them. > + */ > + > + return ops->flags & DMA_F_PCI_P2PDMA_SUPPORTED; Wow, rather unusual combination of things in order decide this. It feels a bit over-complicated to have flags and ops and a bool function all dealing with the same 1-bit answer, but there is no caller shown here, so I'll have to come back to this after reviewing subsequent patches. thanks, -- John Hubbard NVIDIA > +} > +EXPORT_SYMBOL_GPL(dma_pci_p2pdma_supported); > + > #ifdef CONFIG_ARCH_HAS_DMA_SET_MASK > void arch_dma_set_mask(struct device *dev, u64 mask); > #else >