Re: [qemu-s390x] [Qemu-devel] [PATCH v2 1/2] Fix eepro100 simple transmission mode

[Michael Nawrocki]

On 11/16/2017 12:43 PM, Thomas Huth wrote:
> On 16.11.2017 17:59, Thomas Huth wrote:
> > On 06.11.2017 21:35, Mike Nawrocki wrote:
> > > The simple transmission mode was treating the area immediately after the
> > > transmit command block (TCB) as if it were a transmit buffer descriptor,
> > > when in reality it is simply the packet data. This change simply copies
> > > the data following the TCB into the packet buffer.
> > >
> > > Signed-off-by: Mike Nawrocki <address@hidden>
> > > ---
> > >   hw/net/eepro100.c | 18 +++---------------
> > >   1 file changed, 3 insertions(+), 15 deletions(-)
> > >
> > > diff --git a/hw/net/eepro100.c b/hw/net/eepro100.c
> > > index 80b8f47c4b..91dd058010 100644
> > > --- a/hw/net/eepro100.c
> > > +++ b/hw/net/eepro100.c
> > > @@ -774,23 +774,11 @@ static void tx_command(EEPRO100State *s)
> > >       }
> > >       assert(tcb_bytes <= sizeof(buf));
> > >       while (size < tcb_bytes) {
> > > -        uint32_t tx_buffer_address = ldl_le_pci_dma(&s->dev, tbd_address);
> > > -        uint16_t tx_buffer_size = lduw_le_pci_dma(&s->dev, tbd_address + 4);
> > > -#if 0
> > > -        uint16_t tx_buffer_el = lduw_le_pci_dma(&s->dev, tbd_address + 6);
> > > -#endif
> > > -        if (tx_buffer_size == 0) {
> > > -            /* Prevent an endless loop. */
> > > -            logout("loop in %s:%u\n", __FILE__, __LINE__);
> > > -            break;
> > > -        }
> > > -        tbd_address += 8;
> > >           TRACE(RXTX, logout
> > >               ("TBD (simplified mode): buffer address 0x%08x, size 0x%04x\n",
> > > -             tx_buffer_address, tx_buffer_size));
> > > -        tx_buffer_size = MIN(tx_buffer_size, sizeof(buf) - size);
> > > -        pci_dma_read(&s->dev, tx_buffer_address, &buf[size], tx_buffer_size);
> > > -        size += tx_buffer_size;
> > > +             tbd_address, tcb_bytes));
> > > +        pci_dma_read(&s->dev, tbd_address, &buf[size], tcb_bytes);
> > > +        size += tcb_bytes;
> > >       }
> > >       if (tbd_array == 0xffffffff) {
> > >           /* Simplified mode. Was already handled by code above. */
> >
> >   Hi,
> >
> > I've got no clue why, but apparently this patch introduced a regression
> > in rc1: The tests/pxe-test is now failing on a big endian (s390x) host
> > when testing the i82550 device.
> > It's working fine with commit 8fa5ad6dfb66b6c695aa6a6b54b7031c (and
> > 2.11-rc0), and it's broken starting with commit
> > 1865e288a823c764cd4344d704e33344 ... do you have any clue what might be
> > wrong here now?
>
> This patch seems to fix the issue for me:
>
> 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;
>
> Does that make sense? I think the fields are already swapped in
> read_cb(), so no need to swap them in tx_command() again?
>
>   Thomas

That makes sense to me. Not entirely sure why my patch caused the 
regression, but your patch seems like the correct behavior here.

Thanks,
Mike