Re: [PATCH for-5.2] s390x/pci: fix endianness issues

[Matthew Rosato <mjrosato@linux.ibm.com>]

On 11/17/20 12:59 PM, Philippe Mathieu-Daudé wrote:
> On 11/17/20 6:13 PM, Cornelia Huck wrote:
>> zPCI control blocks are big endian, we need to take care that we
>> do proper accesses in order not to break tcg guests on little endian
>> hosts.
>>
>> Fixes: 28dc86a07299 ("s390x/pci: use a PCI Group structure")
>> Fixes: 9670ee752727 ("s390x/pci: use a PCI Function structure")
>> Fixes: 1e7552ff5c34 ("s390x/pci: get zPCI function info from host")
>> Signed-off-by: Cornelia Huck <cohuck@redhat.com>
>> ---
>>
>> Works for me with virtio-pci devices for tcg on x86 and s390x, and for kvm.
>> The vfio changes are not strictly needed; did not test them due to lack of
>> hardware -- testing appreciated. >>
>> As this fixes a regression, I want this in 5.2.
>>
>> ---
>>   hw/s390x/s390-pci-bus.c  | 12 ++++++------
>>   hw/s390x/s390-pci-inst.c |  4 ++--
>>   hw/s390x/s390-pci-vfio.c |  8 ++++----
>>   3 files changed, 12 insertions(+), 12 deletions(-)
>>
>> diff --git a/hw/s390x/s390-pci-bus.c b/hw/s390x/s390-pci-bus.c
>> index e0dc20ce4a56..17e64e0b1200 100644
>> --- a/hw/s390x/s390-pci-bus.c
>> +++ b/hw/s390x/s390-pci-bus.c
>> @@ -787,12 +787,12 @@ static void s390_pci_init_default_group(void)
>>   
>>   static void set_pbdev_info(S390PCIBusDevice *pbdev)
>>   {
>> -    pbdev->zpci_fn.sdma = ZPCI_SDMA_ADDR;
>> -    pbdev->zpci_fn.edma = ZPCI_EDMA_ADDR;
>> -    pbdev->zpci_fn.pchid = 0;
>> +    stq_p(&pbdev->zpci_fn.sdma, ZPCI_SDMA_ADDR);
> 
> "zPCI control blocks are big endian" so don't we
> need the _be_ accessors? stq_be_p() etc...
> 

I don't think this is necessary.  This is only available for target 
s390x, which is always big endian...  cpu-all.h should define stq_p as 
stq_be_p for example inside the #if defined(TARGET_WORDS_BIGENDIAN).