linux-kernel - Re: [PATCH 02/10] PCI/P2PDMA: Introduce p2pdma_provider structure for cleaner abstraction

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Message-ID: <20250724075145.GB30590@lst.de>
Date: Thu, 24 Jul 2025 09:51:45 +0200
From: Christoph Hellwig <hch@....de>
To: Leon Romanovsky <leon@...nel.org>
Cc: Alex Williamson <alex.williamson@...hat.com>,
	Leon Romanovsky <leonro@...dia.com>, Christoph Hellwig <hch@....de>,
	Jason Gunthorpe <jgg@...dia.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Christian König <christian.koenig@....com>,
	dri-devel@...ts.freedesktop.org, iommu@...ts.linux.dev,
	Jens Axboe <axboe@...nel.dk>,
	Jérôme Glisse <jglisse@...hat.com>,
	Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
	linaro-mm-sig@...ts.linaro.org, linux-block@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
	linux-mm@...ck.org, linux-pci@...r.kernel.org,
	Logan Gunthorpe <logang@...tatee.com>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Robin Murphy <robin.murphy@....com>,
	Sumit Semwal <sumit.semwal@...aro.org>,
	Vivek Kasireddy <vivek.kasireddy@...el.com>,
	Will Deacon <will@...nel.org>
Subject: Re: [PATCH 02/10] PCI/P2PDMA: Introduce p2pdma_provider structure
 for cleaner abstraction

On Wed, Jul 23, 2025 at 04:00:03PM +0300, Leon Romanovsky wrote:
> From: Leon Romanovsky <leonro@...dia.com>
> 
> Extract the core P2PDMA provider information (device owner and bus
> offset) from the dev_pagemap into a dedicated p2pdma_provider structure.
> This creates a cleaner separation between the memory management layer and
> the P2PDMA functionality.
> 
> The new p2pdma_provider structure contains:
> - owner: pointer to the providing device
> - bus_offset: computed offset for non-host transactions
> 
> This refactoring simplifies the P2PDMA state management by removing
> the need to access pgmap internals directly. The pci_p2pdma_map_state
> now stores a pointer to the provider instead of the pgmap, making
> the API more explicit and easier to understand.

I really don't see how anything becomes cleaner or simpler here.
It adds a new structure that only exists embedded in the exist one
and more code for no apparent benefit.