linux-kernel - Re: [PATCH 10/10] vfio/pci: Add dma-buf export support for MMIO regions

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Message-ID: <20250730093215.GP402218@unreal>
Date: Wed, 30 Jul 2025 12:32:15 +0300
From: Leon Romanovsky <leon@...nel.org>
To: Jason Gunthorpe <jgg@...dia.com>
Cc: Robin Murphy <robin.murphy@....com>,
	Alex Williamson <alex.williamson@...hat.com>,
	Christoph Hellwig <hch@....de>,
	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>,
	Sumit Semwal <sumit.semwal@...aro.org>,
	Vivek Kasireddy <vivek.kasireddy@...el.com>,
	Will Deacon <will@...nel.org>
Subject: Re: [PATCH 10/10] vfio/pci: Add dma-buf export support for MMIO
 regions

On Tue, Jul 29, 2025 at 05:13:51PM -0300, Jason Gunthorpe wrote:
> On Tue, Jul 29, 2025 at 08:44:21PM +0100, Robin Murphy wrote:
> 
> > In this case with just one single
> > contiguous mapping, it is clearly objectively worse to have to bounce in and
> > out of the IOMMU layer 3 separate times and store a dma_map_state,
> 
> The non-contiguous mappings are comming back, it was in earlier drafts
> of this. Regardless, the point is to show how to use the general API
> that we would want to bring into the DRM drivers that don't have
> contiguity even though VFIO is a bit special.

Yes, we will see comeback of DMA ranges in v2.

Thanks