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

[Stefan Hajnoczi]

On Tue, Oct 22, 2019 at 08:48:31PM +0200, Thomas Huth wrote:
> 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?

I'll try adding a bool field in v4 so there are no problems with a 0
feature bit set.

Stefan

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