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[142.162.112.119]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-50939ec5017sm30688511cf.8.2026.03.12.05.20.59 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 12 Mar 2026 05:20:59 -0700 (PDT) Received: from jgg by wakko with local (Exim 4.97) (envelope-from ) id 1w0f2A-00000006et5-427z; Thu, 12 Mar 2026 09:20:58 -0300 Date: Thu, 12 Mar 2026 09:20:58 -0300 From: Jason Gunthorpe To: Leon Romanovsky Cc: Marek Szyprowski , Robin Murphy , "Michael S. Tsirkin" , Petr Tesarik , Jonathan Corbet , Shuah Khan , Jason Wang , Xuan Zhuo , Eugenio =?utf-8?B?UMOpcmV6?= , Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , Joerg Roedel , Will Deacon , Andrew Morton , iommu@lists.linux.dev, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, virtualization@lists.linux.dev, linux-rdma@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH v2 5/8] dma-direct: prevent SWIOTLB path when DMA_ATTR_REQUIRE_COHERENT is set Message-ID: <20260312122058.GE1469476@ziepe.ca> References: <20260311-dma-debug-overlap-v2-0-e00bc2ca346d@nvidia.com> <20260311-dma-debug-overlap-v2-5-e00bc2ca346d@nvidia.com> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260311-dma-debug-overlap-v2-5-e00bc2ca346d@nvidia.com> On Wed, Mar 11, 2026 at 09:08:48PM +0200, Leon Romanovsky wrote: > From: Leon Romanovsky > > DMA_ATTR_REQUIRE_COHERENT indicates that SWIOTLB must not be used. > Ensure the SWIOTLB path is declined whenever the DMA direct path is > selected. > > Signed-off-by: Leon Romanovsky > --- > kernel/dma/direct.h | 7 ++++--- > 1 file changed, 4 insertions(+), 3 deletions(-) > > diff --git a/kernel/dma/direct.h b/kernel/dma/direct.h > index e89f175e9c2d0..6184ff303f080 100644 > --- a/kernel/dma/direct.h > +++ b/kernel/dma/direct.h > @@ -84,7 +84,7 @@ static inline dma_addr_t dma_direct_map_phys(struct device *dev, > dma_addr_t dma_addr; > > if (is_swiotlb_force_bounce(dev)) { > - if (attrs & DMA_ATTR_MMIO) > + if (attrs & (DMA_ATTR_MMIO | DMA_ATTR_REQUIRE_COHERENT)) > return DMA_MAPPING_ERROR; > > return swiotlb_map(dev, phys, size, dir, attrs); Oh here it is, still maybe it is better to put it in swiotlb_map() ? Jason