linux-kernel - Re: [PATCH 05/10] PCI/P2PDMA: Export pci_p2pdma_map

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: <20250730080317.GO402218@unreal>
Date: Wed, 30 Jul 2025 11:03:17 +0300
From: Leon Romanovsky <leon@...nel.org>
To: Logan Gunthorpe <logang@...tatee.com>
Cc: Jason Gunthorpe <jgg@...dia.com>, Christoph Hellwig <hch@....de>,
	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,
	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 05/10] PCI/P2PDMA: Export pci_p2pdma_map_type() function

On Tue, Jul 29, 2025 at 02:54:13PM -0600, Logan Gunthorpe wrote:
> 
> 
> On 2025-07-28 17:11, Jason Gunthorpe wrote:
> >> If the dma mapping for P2P memory doesn't need to create an iommu
> >> mapping then that's fine. But it should be the dma-iommu layer to decide
> >> that.
> > 
> > So above, we can't use dma-iommu.c, it might not be compiled into the
> > kernel but the dma_map_phys() path is still valid.
> 
> This is an easily solved problem. I did a very rough sketch below to say
> it's really not that hard. (Note it has some rough edges that could be
> cleaned up and I based it off Leon's git repo which appears to not be
> the same as what was posted, but the core concept is sound).

I started to prepare v2, this is why posted version is slightly
different from dmabuf-vfio branch.

In addition to what Jason wrote. there is an extra complexity with using
state. The wrappers which operate on dma_iova_state assume that all memory,
which is going to be mapped, is the same type: or p2p or not.

This is not the cased for HMM/RDMA users, there you create state in
advance and get mixed type of pages.

Thanks