[dpdk-dev] [PATCH dpdk 5/5] RFC: vfio/ppc64/spapr: Use correct bus addresses for DMA map

[Jonas Pfefferle1]

Alexey Kardashevskiy <aik at ozlabs.ru> wrote on 20/04/2017 09:24:02:

> From: Alexey Kardashevskiy <aik at ozlabs.ru>
> To: dev at dpdk.org
> Cc: Alexey Kardashevskiy <aik at ozlabs.ru>, JPF at zurich.ibm.com,
> Gowrishankar Muthukrishnan <gowrishankar.m at in.ibm.com>
> Date: 20/04/2017 09:24
> Subject: [PATCH dpdk 5/5] RFC: vfio/ppc64/spapr: Use correct bus
> addresses for DMA map
>
> VFIO_IOMMU_SPAPR_TCE_CREATE ioctl() returns the actual bus address for
> just created DMA window. It happens to start from zero because the
default
> window is removed (leaving no windows) and new window starts from zero.
> However this is not guaranteed and the new window may start from another
> address, this adds an error check.
>
> Another issue is that IOVA passed to VFIO_IOMMU_MAP_DMA should be a PCI
> bus address while in this case a physical address of a user page is used.
> This changes IOVA to start from zero in a hope that the rest of DPDK
> expects this.

This is not the case. DPDK expects a 1:1 mapping PA==IOVA. It will use the
phys_addr of the memory segment it got from /proc/self/pagemap cf.
librte_eal/linuxapp/eal/eal_memory.c. We could try setting it here to the
actual iova which basically makes the whole virtual to phyiscal mapping
with pagemap unnecessary which I believe should be the case for VFIO
anyway. Pagemap should only be needed when using pci_uio.

>
> Signed-off-by: Alexey Kardashevskiy <aik at ozlabs.ru>
> ---
>  lib/librte_eal/linuxapp/eal/eal_vfio.c | 12 ++++++++++--
>  1 file changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/lib/librte_eal/linuxapp/eal/eal_vfio.c b/lib/
> librte_eal/linuxapp/eal/eal_vfio.c
> index 46f951f4d..8b8e75c4f 100644
> --- a/lib/librte_eal/linuxapp/eal/eal_vfio.c
> +++ b/lib/librte_eal/linuxapp/eal/eal_vfio.c
> @@ -658,7 +658,7 @@ vfio_spapr_dma_map(int vfio_container_fd)
>  {
>     const struct rte_memseg *ms = rte_eal_get_physmem_layout();
>     int i, ret;
> -
> +   phys_addr_t io_offset;
>     struct vfio_iommu_spapr_register_memory reg = {
>        .argsz = sizeof(reg),
>        .flags = 0
> @@ -702,6 +702,13 @@ vfio_spapr_dma_map(int vfio_container_fd)
>        return -1;
>     }
>
> +   io_offset = create.start_addr;
> +   if (io_offset) {
> +      RTE_LOG(ERR, EAL, "  DMA offsets other than zero is not supported,
"
> +            "new window is created at %lx\n", io_offset);
> +      return -1;
> +   }
> +
>     /* map all DPDK segments for DMA. use 1:1 PA to IOVA mapping */
>     for (i = 0; i < RTE_MAX_MEMSEG; i++) {
>        struct vfio_iommu_type1_dma_map dma_map;
> @@ -723,7 +730,7 @@ vfio_spapr_dma_map(int vfio_container_fd)
>        dma_map.argsz = sizeof(struct vfio_iommu_type1_dma_map);
>        dma_map.vaddr = ms[i].addr_64;
>        dma_map.size = ms[i].len;
> -      dma_map.iova = ms[i].phys_addr;
> +      dma_map.iova = io_offset;
>        dma_map.flags = VFIO_DMA_MAP_FLAG_READ |
>               VFIO_DMA_MAP_FLAG_WRITE;
>
> @@ -735,6 +742,7 @@ vfio_spapr_dma_map(int vfio_container_fd)
>           return -1;
>        }
>
> +      io_offset += dma_map.size;
>     }
>
>     return 0;
> --
> 2.11.0
>