Re: [PATCH v3 07/16] libqos: enforce Device Initialization order

[Thomas Huth]

On 22/10/2019 17.48, Stefan Hajnoczi wrote:
> On Mon, Oct 21, 2019 at 02:15:53PM +0200, Thomas Huth wrote:
>> On 19/10/2019 08.38, Stefan Hajnoczi wrote:
>>> According to VIRTIO 1.1 "3.1.1 Driver Requirements: Device
>>> Initialization", configuration space and virtqueues cannot be accessed
>>> before features have been negotiated.  Enforce this requirement.
>>>
>>> Signed-off-by: Stefan Hajnoczi <address@hidden>
>>> ---
>>>  tests/libqos/virtio.c | 11 +++++++++++
>>>  1 file changed, 11 insertions(+)
>>>
>>> diff --git a/tests/libqos/virtio.c b/tests/libqos/virtio.c
>>> index 4f7e6bb8a1..2593996c98 100644
>>> --- a/tests/libqos/virtio.c
>>> +++ b/tests/libqos/virtio.c
>>> @@ -13,23 +13,33 @@
>>>  #include "standard-headers/linux/virtio_config.h"
>>>  #include "standard-headers/linux/virtio_ring.h"
>>>  
>>> +/* Features must be negotiated before config space or virtqueue access */
>>> +static void check_features_negotiated(QVirtioDevice *d)
>>> +{
>>> +    g_assert_cmphex(d->features, !=, 0);
>>> +}
>>
>> Isn't it "legal" to negotiate 0 feature bits, too (for legacy devices)?
> 
> Yes, it's possible for Legacy devices.  If someone ever does that
> they'll need to extend this code, but it's unlikely so I'd rather not
> complicate this.

Could you please add at least a comment here with that explanation?

 Thanks,
  Thomas