Re: [Qemu-ppc] [PATCH 4/4] tests: enable ohci/uhci/xhci tests on PPC64

[Laurent Vivier]

On 27/09/2016 05:53, David Gibson wrote:
> On Mon, Sep 26, 2016 at 04:10:49PM +0200, Laurent Vivier wrote:

>>  void qusb_pci_init_one(QPCIBus *pcibus, struct qhc *hc, uint32_t devfn, int 
>> bar)
>>  {
>>      hc->dev = qpci_device_find(pcibus, devfn);
>> @@ -31,6 +38,13 @@ void uhci_port_test(struct qhc *hc, int port, uint16_t 
>> expect)
>>      uint16_t value = qpci_io_readw(hc->dev, addr);
>>      uint16_t mask = ~(UHCI_PORT_WRITE_CLEAR | UHCI_PORT_RSVD1);
>>  
>> +    if (qtest_big_endian() && host_big_endian) {
>> +        /* little endian device on big endian guest
>> +         * must be swapped on big endian host
>> +         */
>> +        value = bswap16(value);
>> +    }
>> +
> 
> Hm.. should the qpci_io_*() helpers handle the endian conversion?

I'm really wondering how to manage correctly this case (I've the same
kind of issue with virtio).

The protocol between guest and test program reads/writes data using the
guest CPU endianess, so it works in the overall case. But in this case,
hcd-uhci is a little-endian device (.endianness = DEVICE_LITTLE_ENDIAN)
on a big endian machine, so I think in the linux driver we should have a
"le16_to_cpu()". But in our case we can't use "le16_to_cpu()" because
endianess of the host cpu is not the same has the one of the guest CPU.
Perhaps I should add a "target_le16_to_cpu()"?

Thanks,
Laurent