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Date: Wed, 13 Mar 2024 09:46:36 +0200
From: Leon Romanovsky <leon@kernel.org>
To: Christoph Hellwig <hch@lst.de>
Cc: Jason Gunthorpe <jgg@ziepe.ca>, Robin Murphy <robin.murphy@arm.com>,
	Marek Szyprowski <m.szyprowski@samsung.com>,
	Joerg Roedel <joro@8bytes.org>, Will Deacon <will@kernel.org>,
	Chaitanya Kulkarni <chaitanyak@nvidia.com>,
	Jonathan Corbet <corbet@lwn.net>, Jens Axboe <axboe@kernel.dk>,
	Keith Busch <kbusch@kernel.org>, Sagi Grimberg <sagi@grimberg.me>,
	Yishai Hadas <yishaih@nvidia.com>,
	Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>,
	Kevin Tian <kevin.tian@intel.com>,
	Alex Williamson <alex.williamson@redhat.com>,
	=?iso-8859-1?B?Suly9G1l?= Glisse <jglisse@redhat.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	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,
	kvm@vger.kernel.org, linux-mm@kvack.org,
	Bart Van Assche <bvanassche@acm.org>,
	Damien Le Moal <damien.lemoal@opensource.wdc.com>,
	Amir Goldstein <amir73il@gmail.com>,
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	"Martin K. Petersen" <martin.petersen@oracle.com>,
	"daniel@iogearbox.net" <daniel@iogearbox.net>,
	Dan Williams <dan.j.williams@intel.com>,
	"jack@suse.com" <jack@suse.com>, Zhu Yanjun <zyjzyj2000@gmail.com>
Subject: Re: [RFC RESEND 00/16] Split IOMMU DMA mapping operation to two steps
Message-ID: <20240313074636.GV12921@unreal>
References: <20240306174456.GO9225@ziepe.ca>
 <20240306221400.GA8663@lst.de>
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 <20240307150505.GA28978@lst.de>
 <20240307210116.GQ9225@ziepe.ca>
 <20240308164920.GA17991@lst.de>
 <20240308202342.GZ9225@ziepe.ca>
 <20240309161418.GA27113@lst.de>
 <20240310093513.GB12921@unreal>
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In-Reply-To: <20240312212844.GA3018@lst.de>

On Tue, Mar 12, 2024 at 10:28:44PM +0100, Christoph Hellwig wrote:
> On Sun, Mar 10, 2024 at 11:35:13AM +0200, Leon Romanovsky wrote:
> > And you will need to have a way to instruct that pin_user_pages() variant
> > to continue anyway, because you asked for FOLL_PCI_P2PDMA. Without that
> > force, you will have !FOLL_PCI_P2PDMA behaviour.
> 
> I don't understand what you mean.

Jason talked about the need to call to pin_user_pages(..., gup_flags | FOLL_PCI_P2PDMA, ...),
but in your proposal this call won't be possible anymore.

> 
> > When you say "simplify the overall interface", which interface do you mean?
> 
> Primarily the dma mapping interface.  Secondarily also everything around
> it.

OK, thanks