Re: [PATCH v2 7/7] libqos: add VIRTIO PCI 1.0 support

[Stefan Hajnoczi]

On Thu, Oct 17, 2019 at 04:52:54PM +0200, Thomas Huth wrote:
> On 11/10/2019 10.56, Stefan Hajnoczi wrote:
> > Implement the VIRTIO 1.0 virtio-pci interface.  The main change here is
> > that the register layout is no longer a fixed layout in BAR 0.  Instead
> > we have to iterate of PCI Capabilities to find descriptions of where
> > various registers are located.  The vring registers are also more
> > fine-grained, allowing for more flexible vring layouts, but we don't
> > take advantage of that.
> > 
> > Note that test cases do not negotiate VIRTIO_F_VERSION_1 yet and are
> > therefore not running in VIRTIO 1.0 mode.
> > 
> > Signed-off-by: Stefan Hajnoczi <address@hidden>
> > ---
> >  tests/Makefile.include           |   1 +
> >  tests/libqos/virtio-pci-modern.h |  17 ++
> >  tests/libqos/virtio-pci.h        |  10 +
> >  tests/libqos/virtio-pci-modern.c | 412 +++++++++++++++++++++++++++++++
> >  tests/libqos/virtio-pci.c        |   6 +-
> >  5 files changed, 445 insertions(+), 1 deletion(-)
> >  create mode 100644 tests/libqos/virtio-pci-modern.h
> >  create mode 100644 tests/libqos/virtio-pci-modern.c
> [...]
> > +static bool probe_device_type(QVirtioPCIDevice *dev)
> > +{
> > +    uint16_t vendor_id;
> > +    uint16_t device_id;
> > +
> > +    /* "Drivers MUST match devices with the PCI Vendor ID 0x1AF4" */
> > +    vendor_id = qpci_config_readw(dev->pdev, PCI_VENDOR_ID);
> > +    if (vendor_id != 0x1af4) {
> > +        return false;
> > +    }
> > +
> > +    /*
> > +     * "Any PCI device with ... PCI Device ID 0x1000 through 0x107F 
> > inclusive
> > +     * is a virtio device"
> > +     */
> > +    device_id = qpci_config_readw(dev->pdev, PCI_DEVICE_ID);
> > +    if (device_id < 0x1000 || device_id > 0x107f) {
> > +        return false;
> > +    }
> > +
> > +    /*
> > +     * "Devices MAY utilize a Transitional PCI Device ID range, 0x1000 to
> > +     * 0x103F depending on the device type"
> > +     */
> > +    if (device_id < 0x1040) {
> > +        /*
> > +         * "Transitional devices MUST have the PCI Subsystem Device ID 
> > matching
> > +         * the Virtio Device ID"
> > +         */
> > +        dev->vdev.device_type = qpci_config_readw(dev->pdev, 
> > PCI_SUBSYSTEM_ID);
> 
> Shouldn't you return "false" here in case the device_type is 0 ? Which
> likely means that it is a legacy or broken device ...?

The real decision whether to use this PCI device or not happens in
probe_device_layout().  If it's broken or a legacy device then that
function will fail.

Stefan

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