Re: [Qemu-devel] [PATCH] rtl8139: Fix invalid IO access alignment

[Stefan Hajnoczi]

On Sun, Nov 13, 2011 at 6:13 PM, Julian Pidancet
<address@hidden> wrote:
> This patch makes iPXE work with the rtl8139 emulation. The rtl8139
> driver in iPXE issues a 16bit access on the ChipCmd register
> (offset 0x37) to check the status of the rx buffer. The offset of the
> ioport access was getting fixed up to 0x36 in qemu, causing the value
> read in iPXE to be invalid.
>
> This fixes an issue with iPXE reporting timeouts during TFTP transfers.
>
> Signed-off-by: Julian Pidancet <address@hidden>
> ---
>  hw/rtl8139.c |   10 +++++-----
>  1 files changed, 5 insertions(+), 5 deletions(-)

I checked the datasheet and the register byte at 0x38, after ChipCmd,
is undocumented.  iPXE is being weird, I don't see the reason for the
inw().

> @@ -2800,7 +2800,7 @@ static void rtl8139_io_writew(void *opaque, uint8_t 
> addr, uint32_t val)
>  {
>     RTL8139State *s = opaque;
>
> -    addr &= 0xfe;
> +    addr &= 0xff;

You can simply drop the masking since
rtl8139_ioport_readw()/rtl8139_mmio_readw() already do addr & 0xFF.
Same applies for the other hunks in this patch.

Stefan