Re: [dpdk-dev] [PATCH 6/7] virtio: fix pci accesses for ppc64 in legacy mode

[David Marchand <david.marchand@6wind.com>]

Hello Olivier,

On Fri, May 13, 2016 at 2:50 PM, Olivier Matz <olivier.matz@6wind.com> wrote:
> From: David Marchand <david.marchand@6wind.com>
>
> Although ppc supports both endianesses, qemu supposes that the cpu is
> big endian and enforces this for the virtio-net stuff.
>
> Fix PCI accesses in legacy mode. Only ppc64le is supported at the moment.
>
> Signed-off-by: David Marchand <david.marchand@6wind.com>
> Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
> ---
>  drivers/net/virtio/virtio_pci.c | 44 +++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 44 insertions(+)
>
> diff --git a/drivers/net/virtio/virtio_pci.c b/drivers/net/virtio/virtio_pci.c
> index 9cdca06..bdb89fd 100644
> --- a/drivers/net/virtio/virtio_pci.c
> +++ b/drivers/net/virtio/virtio_pci.c
> @@ -55,18 +55,62 @@
>   */
>  #define VIRTIO_PCI_CONFIG(hw) (((hw)->use_msix) ? 24 : 20)
>
> +/*
> + * Since we are in legacy mode:
> + * http://ozlabs.org/~rusty/virtio-spec/virtio-0.9.5.pdf
> + *
> + * "Note that this is possible because while the virtio header is PCI (i.e.
> + * little) endian, the device-specific region is encoded in the native endian of
> + * the guest (where such distinction is applicable)."
> + *
> + * For powerpc which supports both, qemu supposes that cpu is big endian and
> + * enforces this for the virtio-net stuff.
> + */
> +
>  static void
>  legacy_read_dev_config(struct virtio_hw *hw, size_t offset,
>                        void *dst, int length)
>  {
>         rte_eal_pci_ioport_read(&hw->io, dst, length,
>                                 VIRTIO_PCI_CONFIG(hw) + offset);
> +#ifdef RTE_ARCH_PPC_64
> +       switch (length) {
> +       case 4:
> +               *(uint32_t *)dst = rte_be_to_cpu_32(*(uint32_t *)dst);
> +               break;
> +       case 2:
> +               *(uint16_t *)dst = rte_be_to_cpu_16(*(uint16_t *)dst);
> +               break;
> +       default:
> +               break;
> +       }
> +#endif
>  }

I think that, in the original patch, I was handling lengths different
than 1, 2 and 4 ;-)
Idem for write.


-- 
David Marchand