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Date: Fri, 8 Nov 2024 16:05:00 +0100
From: Christoph Hellwig <hch@lst.de>
To: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Christoph Hellwig <hch@lst.de>, Robin Murphy <robin.murphy@arm.com>,
	Leon Romanovsky <leon@kernel.org>, Jens Axboe <axboe@kernel.dk>,
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	=?iso-8859-1?B?Suly9G1l?= Glisse <jglisse@redhat.com>,
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Subject: Re: [PATCH v1 00/17] Provide a new two step DMA mapping API
Message-ID: <20241108150500.GA10102@lst.de>
References: <cover.1730298502.git.leon@kernel.org> <3567312e-5942-4037-93dc-587f25f0778c@arm.com> <20241104095831.GA28751@lst.de> <20241105195357.GI35848@ziepe.ca> <20241107083256.GA9071@lst.de> <20241107132808.GK35848@ziepe.ca> <20241107135025.GA14996@lst.de> <20241108150226.GM35848@ziepe.ca>
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User-Agent: Mutt/1.5.17 (2007-11-01)

On Fri, Nov 08, 2024 at 11:02:26AM -0400, Jason Gunthorpe wrote:
> It is fully OK? Can't dma_map_page() trigger swiotlb? It must not do
> that for P2P. How does it know the difference if it just gets a phys?

dma_direct_map_page checks for p2p pages in the swiotlb bounce
path already in the current kernel, and dma_map_sg relies on exactly
that check to prevent bouncing for p2p.