Re: [PATCH v5 9/9] vfio/pci: Add dma-buf export support for MMIO regions

Leon Romanovsky
2025-10-20T16:45:03Z

On Mon, Oct 20, 2025 at 01:15:16PM -0300, Jason Gunthorpe wrote:
> On Fri, Oct 17, 2025 at 07:13:58PM +0300, Leon Romanovsky wrote:
> > > static int 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 p2pdma_provider *provider)
> > > {
> > > struct pci_dev *pdev = priv->vdev->pdev;
> > > phys_addr_t len = pci_resource_len(pdev, dma_buf->region_index);
> > > phys_addr_t pci_start;
> > > phys_addr_t pci_last;
> > > u32 i;
> > >
> > > if (!len)
> > > return -EINVAL;
> > > pci_start = pci_resource_start(pdev, dma_buf->region_index);
> > > pci_last = pci_start + len - 1;
> > > for (i = 0; i < dma_buf->nr_ranges; i++) {
> > > phys_addr_t last;
> > >
> > > if (!dma_ranges[i].length)
> > > return -EINVAL;
> > >
> > > if (check_add_overflow(pci_start, dma_ranges[i].offset,
> > > &priv->phys_vec[i].paddr) ||
> > > check_add_overflow(priv->phys_vec[i].paddr,
> > > dma_ranges[i].length - 1, &last))
> > > return -EOVERFLOW;
> > > if (last > pci_last)
> > > return -EINVAL;
> > >
> > > priv->phys_vec[i].len = dma_ranges[i].length;
> > > priv->size += priv->phys_vec[i].len;
> > > }
> > > priv->nr_ranges = dma_buf->nr_ranges;
> > > priv->provider = provider;
> > > return 0;
> > > }
> >
> > I have these checks in validate_dmabuf_input().
> > Do you think that I need to add extra checks?
>
> I think they work better in this function, so I'd move them here.

The main idea for validate_dmabuf_input() is to perform as much as
possible checks before allocating kernel memory.

Thanks

>
> Jason