Re: [PATCH] hw/pci/pci_bridge: ensure PCIe slots have only one slot

[Roman Kagan <rvkagan@yandex-team.ru>]

On Wed, Jul 06, 2022 at 09:38:39PM +0300, Vladimir Sementsov-Ogievskiy wrote:
> On 7/4/22 13:25, Roman Kagan wrote:
> > It's possible to create non-working configurations by attaching a device
> > to a derivative of PCIe slot (pcie-root-port, ioh3420, etc) and
> > specifying a slot number other that zero, e.g.:
> > 
> >      -device pcie-root-port,id=s0,... \
> >      -device virtio-blk-pci,bus=s0,addr=4,...
> > 
> > Make QEMU reject such configurations and only allow addr=0 on the
> > secondary bus of a PCIe slot.
> > 
> > Signed-off-by: Roman Kagan <rvkagan@yandex-team.ru>
> > ---
> >   hw/pci/pci_bridge.c | 5 +++++
> >   1 file changed, 5 insertions(+)
> > 
> > diff --git a/hw/pci/pci_bridge.c b/hw/pci/pci_bridge.c
> > index da34c8ebcd..8b38d5ad3d 100644
> > --- a/hw/pci/pci_bridge.c
> > +++ b/hw/pci/pci_bridge.c
> > @@ -33,6 +33,7 @@
> >   #include "qemu/units.h"
> >   #include "hw/pci/pci_bridge.h"
> >   #include "hw/pci/pci_bus.h"
> > +#include "hw/pci/pcie_port.h"
> >   #include "qemu/module.h"
> >   #include "qemu/range.h"
> >   #include "qapi/error.h"
> > @@ -386,6 +387,10 @@ void pci_bridge_initfn(PCIDevice *dev, const char *typename)
> >       br->windows = pci_bridge_region_init(br);
> >       QLIST_INIT(&sec_bus->child);
> >       QLIST_INSERT_HEAD(&parent->child, sec_bus, sibling);
> > +
> > +    if (PCIE_SLOT(dev)) {
> 
> Hmm, wouldn't PCIE_SLOT just crash if dev is not pcie slot? As I understand, PCIE_SLOT is finally an OBJECT_CHECK(), which say:
> 
>  * If an invalid object is passed to this function, a run time assert will be
>  * generated.

Well, the assertion is there only if configured with
--enable-qom-cast-debug which is off by default, that's why it even
passed make check.  As it stands, it's just a typecast which is a no-op
here, and basically it makes every bridge have only a single slot, which
is wrong of course.

Will rework, thanks!
Roman.