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Date: Sat, 13 Sep 2025 13:19:33 +0300
From: Leon Romanovsky <leon@kernel.org>
To: Alex Mastro <amastro@fb.com>
Cc: Alex Williamson <alex.williamson@redhat.com>,
	Jason Gunthorpe <jgg@nvidia.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Bjorn Helgaas <bhelgaas@google.com>,
	Christian =?iso-8859-1?Q?K=F6nig?= <christian.koenig@amd.com>,
	Christoph Hellwig <hch@lst.de>, dri-devel@lists.freedesktop.org,
	iommu@lists.linux.dev, Jens Axboe <axboe@kernel.dk>,
	Joerg Roedel <joro@8bytes.org>, kvm@vger.kernel.org,
	linaro-mm-sig@lists.linaro.org, linux-block@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-media@vger.kernel.org,
	linux-mm@kvack.org, linux-pci@vger.kernel.org,
	Logan Gunthorpe <logang@deltatee.com>,
	Marek Szyprowski <m.szyprowski@samsung.com>,
	Robin Murphy <robin.murphy@arm.com>,
	Sumit Semwal <sumit.semwal@linaro.org>,
	Vivek Kasireddy <vivek.kasireddy@intel.com>,
	Will Deacon <will@kernel.org>
Subject: Re: [PATCH v1 10/10] vfio/pci: Add dma-buf export support for MMIO
 regions
Message-ID: <20250913101933.GW341237@unreal>
References: <cover.1754311439.git.leon@kernel.org>
 <5e043d8b95627441db6156e7f15e6e1658e9d537.1754311439.git.leon@kernel.org>
 <aMRsoUx/NH/Dspm9@devgpu015.cco6.facebook.com>
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In-Reply-To: <aMRsoUx/NH/Dspm9@devgpu015.cco6.facebook.com>

On Fri, Sep 12, 2025 at 11:55:29AM -0700, Alex Mastro wrote:
> On Mon, Aug 04, 2025 at 04:00:45PM +0300, Leon Romanovsky wrote:
> > +static void dma_ranges_to_p2p_phys(struct vfio_pci_dma_buf *priv,
> > +				   struct vfio_device_feature_dma_buf *dma_buf,
> > +				   struct vfio_region_dma_range *dma_ranges)
> > +{
> > +	struct pci_dev *pdev = priv->vdev->pdev;
> > +	phys_addr_t pci_start;
> > +	int i;
> > +
> > +	pci_start = pci_resource_start(pdev, dma_buf->region_index);
> > +	for (i = 0; i < dma_buf->nr_ranges; i++) {
> > +		priv->phys_vec[i].len = dma_ranges[i].length;
> > +		priv->phys_vec[i].paddr += pci_start + dma_ranges[i].offset;
> 
> Is the intent really to += paddr? I would have expected a plain assignment.

In this specific case, there is no difference, because phys_vec is
initialized to 0, but It needs to be "=" and not "+=".

> 
> > +		priv->size += priv->phys_vec[i].len;
> > +	}
> > +	priv->nr_ranges = dma_buf->nr_ranges;
> > +}
> 
> ...
> 
> > +	priv->phys_vec = kcalloc(get_dma_buf.nr_ranges, sizeof(*priv->phys_vec),
> > +				 GFP_KERNEL);
> > +	if (!priv->phys_vec) {
> > +		ret = -ENOMEM;
> > +		goto err_free_priv;
> > +	}
> > +
> > +	priv->vdev = vdev;
> > +	dma_ranges_to_p2p_phys(priv, &get_dma_buf, dma_ranges);
>