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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20250729104100.GA29053@lst.de>
Date: Tue, 29 Jul 2025 12:41:00 +0200
From: Christoph Hellwig <hch@....de>
To: Leon Romanovsky <leon@...nel.org>
Cc: Christoph Hellwig <hch@....de>, Jason Gunthorpe <jgg@...dia.com>,
	Alex Williamson <alex.williamson@...hat.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 Tue, Jul 29, 2025 at 11:53:36AM +0300, Leon Romanovsky wrote:
> > Because the struct page is the only thing that:
> > 
> >  a) dma-mapping works on
> >  b) is the only place we can discover the routing information, but also
> >     more importantly ensure that the underlying page is still present
> >     and the device is not hot unplugged, or in a very theoretical worst
> >     case replaced by something else.
> 
> It is correct in general case, but here we are talking about MMIO
> memory, which is "connected" to device X and routing information is
> stable.

MMIO is literally the only thing we support to P2P to/from as that is
how PCIe P2P is defined.  And not, it's not stable - devices can be
unplugged, and BARs can be reenumerated.