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Message-ID: <20240324231611.GB20765@lst.de>
Date: Mon, 25 Mar 2024 00:16:11 +0100
From: Christoph Hellwig <hch@....de>
To: Leon Romanovsky <leon@...nel.org>
Cc: Christoph Hellwig <hch@....de>, Jason Gunthorpe <jgg@...pe.ca>,
Robin Murphy <robin.murphy@....com>,
Marek Szyprowski <m.szyprowski@...sung.com>,
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Chaitanya Kulkarni <chaitanyak@...dia.com>,
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Keith Busch <kbusch@...nel.org>, Sagi Grimberg <sagi@...mberg.me>,
Yishai Hadas <yishaih@...dia.com>,
Shameer Kolothum <shameerali.kolothum.thodi@...wei.com>,
Kevin Tian <kevin.tian@...el.com>,
Alex Williamson <alex.williamson@...hat.com>,
Jérôme Glisse <jglisse@...hat.com>,
Andrew Morton <akpm@...ux-foundation.org>,
linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-block@...r.kernel.org, linux-rdma@...r.kernel.org,
iommu@...ts.linux.dev, linux-nvme@...ts.infradead.org,
kvm@...r.kernel.org, linux-mm@...ck.org,
Bart Van Assche <bvanassche@....org>,
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Amir Goldstein <amir73il@...il.com>,
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"Martin K. Petersen" <martin.petersen@...cle.com>,
"daniel@...earbox.net" <daniel@...earbox.net>,
Dan Williams <dan.j.williams@...el.com>,
"jack@...e.com" <jack@...e.com>, Zhu Yanjun <zyjzyj2000@...il.com>
Subject: Re: [RFC RESEND 00/16] Split IOMMU DMA mapping operation to two
steps
On Fri, Mar 22, 2024 at 07:46:17PM +0200, Leon Romanovsky wrote:
> > As far as I can tell it totally misses the point. Which is not to never
> > return non-P2P if the flag is set, but to return either all P2P or non-P2
> > P and not create a boundary in the single call.
>
> You are treating FOLL_PCI_P2PDMA as a hint, but in iov_iter_extract_user_pages()
> you set it only for p2p queues. I was under impression that you want only p2p pages
> in these queues.
FOLL_PCI_P2PDMA is an indicator that the caller can cope with P2P
pages. Most callers simply can't.
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