next-20250627: IOMMU DMA warning during NVMe I/O completion after 06cae0e3f61c

[Keith Busch]

On Mon, Jun 30, 2025 at 02:25:23PM -0600, Keith Busch wrote:
> On Mon, Jun 30, 2025 at 03:33:43PM +0200, Christoph Hellwig wrote:
> --- a/drivers/nvme/host/pci.c
> +++ b/drivers/nvme/host/pci.c
> @@ -701,7 +701,7 @@ static void nvme_free_prps(struct request *req)
>         prp_list = iod->descriptors[desc];
>         do {
>                 dma_unmap_page(dma_dev, dma_addr, dma_len, dir);
> -               if (i == NVME_CTRL_PAGE_SIZE >> 3) {
> +               if (i == NVME_CTRL_PAGE_SIZE >> 3 && length > NVME_CTRL_PAGE_SIZE) {
>                         prp_list = iod->descriptors[++desc];
>                         i = 0;
>                 }
> --
> 
> But even that, the PRP setup doesn't match the teardown. We're calling
> dma_map_page() on each PRP even if consecutive PRP's [...]

Err, I meant to say "dma_unmap_page()".