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b=QEmveI2NZTQJ8iB0oY/nED15Zobh8Lap9Ozk9y+25JoYHnQ/y87nbfEHvfKJTJ8Ex sfPWjATkYROgOP3lU8RC5va+oGpgsEBlqrziNnUWdFDy9QJPuBQEtGgkMS4ZDGwukD HALkgjvyTWxvfY+RmLi7pk4eZXuNROOLUMKiKyGsdmjv0qJF35J6VsGLjRWEChoQvS i3INY+wUl2b2QhDxuL2Ya0G5XbUvzLJRJw99SXw+pzDZdqKZ4j52bQcoQZ3UGY9Ybd QPfGwHv/EKf7hPKS8HZIe8cvC2khmqpcwfVdT7JN6XXNbHS2SFK78DFC6fHF1bbD1u stakc0GvtjnfQ== Date: Mon, 28 Oct 2024 20:31:21 +0200 From: Leon Romanovsky To: Baolu Lu Cc: Jens Axboe , Jason Gunthorpe , Robin Murphy , Joerg Roedel , Will Deacon , Christoph Hellwig , Sagi Grimberg , Keith Busch , Bjorn Helgaas , Logan Gunthorpe , Yishai Hadas , Shameer Kolothum , Kevin Tian , Alex Williamson , Marek Szyprowski , =?iso-8859-1?B?Suly9G1l?= Glisse , Andrew Morton , Jonathan Corbet , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, linux-rdma@vger.kernel.org, iommu@lists.linux.dev, linux-nvme@lists.infradead.org, linux-pci@vger.kernel.org, kvm@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 07/18] dma-mapping: Implement link/unlink ranges API Message-ID: <20241028183121.GI1615717@unreal> References: <6a9366a5-7c5b-449c-b259-8e2492aae2a1@linux.intel.com> <20241028062252.GC1615717@unreal> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20241028062252.GC1615717@unreal> X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: E95F014000B X-Stat-Signature: ernabh4b4ky84eqeoh88pa5ekxr9d5y5 X-Rspam-User: X-HE-Tag: 1730140272-956631 X-HE-Meta: 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 lV7uNu8w hrJ7YnVIpICIBtiLYCycpGWaxUqqn4RHU6uYS6ZfIlH68f+sU1gOvI8XdBNpDz8sE+/5v+Lss+iWmTDO0eaa8i3yd9E9KPHHAq+OhgseylQ/Bvm5u6DnmgDX+wbD9qdP7tkb865GbaVFGSNz9P8K3RnixQB5SoMcmW4sWPGEEGU7CSDoJU3EEwDmFtkM8rFFo4yqak0wF9DbmrOk6AryqJJj2ZiF9eJqVqJCyWqRW5I6GO2u4U65m74ow7NRz6cVJ1ZNK X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Oct 28, 2024 at 08:22:52AM +0200, Leon Romanovsky wrote: > On Mon, Oct 28, 2024 at 10:00:25AM +0800, Baolu Lu wrote: > > On 2024/10/27 22:21, Leon Romanovsky wrote: > > > +/** > > > + * dma_iova_sync - Sync IOTLB > > > + * @dev: DMA device > > > + * @state: IOVA state > > > + * @offset: offset into the IOVA state to sync > > > + * @size: size of the buffer > > > + * @ret: return value from the last IOVA operation > > > + * > > > + * Sync IOTLB for the given IOVA state. This function should be called on > > > + * the IOVA-contigous range created by one ore more dma_iova_link() calls > > > + * to sync the IOTLB. > > > + */ > > > +int dma_iova_sync(struct device *dev, struct dma_iova_state *state, > > > + size_t offset, size_t size, int ret) > > > +{ > > > + struct iommu_domain *domain = iommu_get_dma_domain(dev); > > > + struct iommu_dma_cookie *cookie = domain->iova_cookie; > > > + struct iova_domain *iovad = &cookie->iovad; > > > + dma_addr_t addr = state->addr + offset; > > > + size_t iova_start_pad = iova_offset(iovad, addr); > > > + > > > + addr -= iova_start_pad; > > > + size = iova_align(iovad, size + iova_start_pad); > > > + > > > + if (!ret) > > > + ret = iommu_sync_map(domain, addr, size); > > > + if (ret) > > > + iommu_unmap(domain, addr, size); > > > > It appears strange that mapping is not done in this helper, but > > unmapping is added in the failure path. Perhaps I overlooked anything? > > Like iommu_sync_map() is performed on whole continuous range, the iommu_unmap() > should be done on the same range. So, technically you can unmap only part of > the range which called to dma_iova_link() and failed, but you will need > to make sure that iommu_sync_map() is still called for "successful" part of > iommu_map(). > > In that case, you will need to undo everything anyway and it means that > you will call to iommu_unmap() on the successful part of the range > anyway. > > dma_iova_sync() is single operation for the whole range and > iommu_unmap() too, so they are bound together. > > > To my understanding, it should like below: > > > > return iommu_sync_map(domain, addr, size); > > > > In the drivers that make use of this interface should do something like > > below: > > > > ret = dma_iova_sync(...); > > if (ret) > > dma_iova_destroy(...) > > It is actually what is happening in the code, but in less direct way due > to unwinding of the code. After more thoughts on the topic, I think that it will be better to make this dma_iova_sync() less cryptic and more direct. I will change it to be as below in my next version: 1972 int dma_iova_sync(struct device *dev, struct dma_iova_state *state, 1973 size_t offset, size_t size) 1974 { 1975 struct iommu_domain *domain = iommu_get_dma_domain(dev); 1976 struct iommu_dma_cookie *cookie = domain->iova_cookie; 1977 struct iova_domain *iovad = &cookie->iovad; 1978 dma_addr_t addr = state->addr + offset; 1979 size_t iova_start_pad = iova_offset(iovad, addr); 1980 1981 return iommu_sync_map(domain, addr - iova_start_pad, 1982 iova_align(iovad, size + iova_start_pad)); 1983 } 1984 EXPORT_SYMBOL_GPL(dma_iova_sync); Thanks