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b=O1xqE+mqwh8U+55fROspjUrKNzRVSIzJfDGM+Ls83njMJYStvF3kCZtrxDGnS8SVT FH2Y3/4QmPSaIrhVwSXIBJfNKQb2jOqg/0R9XOlNO+8e0XTTOVDsgTNzItS/cuPjFL PJCX+bYuGxOwMqFXAxDt9oJubodYIurQ+knbiSyXMkoJmOUGIl6AyOiN49LQkcuXwW lX4Zt8yUC+E7ZRN3ptmo7qa1Dn9p3RQqNw+5yoy5YM9m0zO7K7IBGHJkXHsUDSieM4 qCQegX3jtiPkdIH87I9vQ2L9GafYOjlgT1bfZh8UZrFfu8pXhN2WP2XoeZGCszveQ5 tJLYM5tBLk6AQ== Date: Sun, 27 Apr 2025 10:25:07 +0300 From: Leon Romanovsky To: Luis Chamberlain Cc: Marek Szyprowski , Jens Axboe , Christoph Hellwig , Keith Busch , Jake Edge , Jonathan Corbet , Jason Gunthorpe , Zhu Yanjun , Robin Murphy , Joerg Roedel , Will Deacon , Sagi Grimberg , Bjorn Helgaas , Logan Gunthorpe , Yishai Hadas , Shameer Kolothum , Kevin Tian , Alex Williamson , =?iso-8859-1?B?Suly9G1l?= Glisse , Andrew Morton , 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, Niklas Schnelle , Chuck Lever , Matthew Wilcox , Dan Williams , Kanchan Joshi , Chaitanya Kulkarni Subject: Re: [PATCH v9 01/24] PCI/P2PDMA: Refactor the p2pdma mapping helpers Message-ID: <20250427072507.GB5848@unreal> References: <3a962f9039f0265de939f4c81924ee8208fc93a6.1745394536.git.leon@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 6F2B81A0005 X-Stat-Signature: zqpjoi6hq6r4twoo1kcb4xgizk8oifqa X-Rspam-User: X-HE-Tag: 1745738713-822569 X-HE-Meta: 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 +uGUR6QO xBpnWnDcDaI1Kj7rMDT0tMm2EpWzePaQvKku9+V7owBsu+a4AGfFlN6i8V7b3QkPZwzSTnrzMmonVDWtPd0YxPzkaE3YDEyVv9nPKaAu6iOrJ/A0Hs+NYSphaZ08Tq2REsJ5zUwqriss04qfA0aR+ijUyhQ1zANSQTR8KJ1u0DbIEixWfVkLMwtwie1bfSHnTLb95NK0jKL8Y3pqLz/1tW7DAu/+4Rqdl4X0wj5+G4hkdQduYXLCc7RWSbpE+AL+TNIYWzkLkvmjhq6DKATm9HkiAmrUtrzJFW7+aHhtSnIqx+UeTZIrUVVVpE/bBPK93U+g+Re/6Y6tlqiVlu2M3RnVq+SdrD8mrK0+rsTIizHB5JGTR7HJeTha3V5gN5Z7Frm8fI6ylCAtoXydbDLjfJJ2LEdEMqKRfjYY8 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 Fri, Apr 25, 2025 at 05:21:59PM -0700, Luis Chamberlain wrote: > On Wed, Apr 23, 2025 at 11:12:52AM +0300, Leon Romanovsky wrote: > > From: Christoph Hellwig > > > > The current scheme with a single helper to determine the P2P status > > and map a scatterlist segment force users to always use the map_sg > > helper to DMA map, which we're trying to get away from because they > > are very cache inefficient. > > > > Refactor the code so that there is a single helper that checks the P2P > > state for a page, including the result that it is not a P2P page to > > simplify the callers, and a second one to perform the address translation > > for a bus mapped P2P transfer that does not depend on the scatterlist > > structure. > > > > Signed-off-by: Christoph Hellwig > > Reviewed-by: Logan Gunthorpe > > Acked-by: Bjorn Helgaas > > Tested-by: Jens Axboe > > Signed-off-by: Leon Romanovsky > > Might make it easier for patch review to split off adding > __pci_p2pdma_update_state() in a seprate patch first. Original code __pci_p2pdma_update_state() had this code and was dependent on SG, which we are removing in this patch. if (state->map == PCI_P2PDMA_MAP_BUS_ADDR) { sg->dma_address = sg_phys(sg) + state->bus_off; sg_dma_len(sg) = sg->length; sg_dma_mark_bus_address(sg); } So to split, we would need to introduce new version of __pci_p2pdma_update_state(), rename existing one to something like __pci_p2pdma_update_state2() and remove it in next patch. Such pattern of adding and immediately deleting code is not welcomed. > Other than that, looks good. > > Reviewed-by: Luis Chamberlain Thanks > > Luis