> diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c
> index baf476039396..20c834cfd2d3 100644
> --- a/drivers/pci/p2pdma.c
> +++ b/drivers/pci/p2pdma.c
> @@ -874,6 +874,91 @@ void pci_p2pdma_unmap_sg_attrs(struct device *dev,
> struct scatterlist *sg,
> }
> EXPORT_SYMBOL_GPL(pci_p2pdma_unmap_sg_attrs);
>
> +static pci_bus_addr_t pci_p2pdma_phys_to_bus(struct pci_dev *dev,
> + phys_addr_t start, size_t size)
> +{
> + struct pci_host_bridge *bridge = pci_find_host_bridge(dev->bus);
> + phys_addr_t end = start + size;
> + struct resource_entry *window;
> +
> + resource_list_for_each_entry(window, &bridge->windows) {
> + if (window->res->start <= start && window->res->end >= end)
> + return start - window->offset;
> + }
> +
> + return DMA_MAPPING_ERROR;
This does once again look very expensive for something called in the
hot path.
