Re: [PATCH for-7.2 v3 2/3] rtl8139: keep Tx command mode 0 and 1 separate

[Jason Wang]

On Fri, Nov 18, 2022 at 12:56 AM Stefan Hajnoczi <stefanha@redhat.com> wrote:
>
> There are two Tx Descriptor formats called mode 0 and mode 1. The mode
> is determined by the Large Send bit.
>
> CP_TX_IPCS (bit 18) is defined in mode 1 but the code checks the bit
> unconditionally. In mode 0 bit 18 is part of the Large Send MSS value.
>
> Explicitly check the Large Send bit to distinguish Tx command modes.
> This avoids bugs where modes are confused. Note that I didn't find any
> actual bugs aside from needlessly computing the IP checksum when the
> Large Send bit is enabled.
>
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

Acked-by: Jason Wang <jasowang@redhat.com>

Thanks

> ---
>  hw/net/rtl8139.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/hw/net/rtl8139.c b/hw/net/rtl8139.c
> index ffef3789b5..6dd7a8e6e0 100644
> --- a/hw/net/rtl8139.c
> +++ b/hw/net/rtl8139.c
> @@ -2135,7 +2135,7 @@ static int rtl8139_cplus_transmit_one(RTL8139State *s)
>              }
>              ip_data_len -= hlen;
>
> -            if (txdw0 & CP_TX_IPCS)
> +            if (!(txdw0 & CP_TX_LGSEN) && (txdw0 & CP_TX_IPCS))
>              {
>                  DPRINTF("+++ C+ mode need IP checksum\n");
>
> @@ -2268,7 +2268,7 @@ static int rtl8139_cplus_transmit_one(RTL8139State *s)
>                  /* Stop sending this frame */
>                  saved_size = 0;
>              }
> -            else if (txdw0 & (CP_TX_TCPCS|CP_TX_UDPCS))
> +            else if (!(txdw0 & CP_TX_LGSEN) && (txdw0 & 
> (CP_TX_TCPCS|CP_TX_UDPCS)))
>              {
>                  DPRINTF("+++ C+ mode need TCP or UDP checksum\n");
>
> --
> 2.38.1
>