Re: [Qemu-devel] [PATCH for-2.11] hw/net/eepro100: Fix endianness problem on big endian hosts

["Michael S. Tsirkin" <mst@redhat.com>]

On Thu, Nov 16, 2017 at 10:16:54PM +0100, Thomas Huth wrote:
> Since commit 1865e288a823c764cd4344d ("Fix eepro100 simple transmission
> mode"), the test/pxe-test is broken for the eepro100 device on big
> endian hosts. However, it seems like that commit did not introduce the
> problem, but just uncovered it: The EEPRO100State->tx.tbd_array_addr and
> EEPRO100State->tx.tcb_bytes fields are already in host byte order, since
> they have already been byte-swapped in the read_cb() function.
> Thus byte-swapping them in tx_command() again results in the wrong
> endianness. Removing the byte-swapping here fixes the pxe-test.
> 
> Signed-off-by: Thomas Huth <thuth@redhat.com>


Reviewed-by: Michael S. Tsirkin <mst@redhat.com>

Thomas, how about adding sparse endian-ness annotations
a la le32 in Linux? We could then use static checkers to
catch these bugs at build time.

> ---
>  hw/net/eepro100.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/net/eepro100.c b/hw/net/eepro100.c
> index a63ed2c..03e00f7 100644
> --- a/hw/net/eepro100.c
> +++ b/hw/net/eepro100.c
> @@ -756,8 +756,8 @@ static void read_cb(EEPRO100State *s)
>  
>  static void tx_command(EEPRO100State *s)
>  {
> -    uint32_t tbd_array = le32_to_cpu(s->tx.tbd_array_addr);
> -    uint16_t tcb_bytes = (le16_to_cpu(s->tx.tcb_bytes) & 0x3fff);
> +    uint32_t tbd_array = s->tx.tbd_array_addr;
> +    uint16_t tcb_bytes = s->tx.tcb_bytes & 0x3fff;
>      /* Sends larger than MAX_ETH_FRAME_SIZE are allowed, up to 2600 bytes. */
>      uint8_t buf[2600];
>      uint16_t size = 0;
> -- 
> 1.8.3.1