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

[Stefan Hajnoczi]

On Mon, Nov 14, 2011 at 2:46 PM, Julian Pidancet
<address@hidden> wrote:
> On Mon, Nov 14, 2011 at 2:38 PM, Stefan Hajnoczi <address@hidden> wrote:
>> 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().
>>
>
> I agree, changing this inw() to an inb() in iPXE also fixes the issue.
> But this patch makes more sense because it reflects how real hardware
> would behave.

Yep, we need to support real-world (weird) software.  Sending a patch
to iPXE is good, but QEMU should work with existing iPXE builds.

Stefan