Re: [Qemu-devel] [PATCH v2 2/3] hw/pci: add teardown function for PCI resource reserve capability

[Marcel Apfelbaum]

Hi Jing,

On 08/20/2018 05:58 AM, Liu, Jing2 wrote:
> Hi Marcel,
>
> On 8/18/2018 12:10 AM, Marcel Apfelbaum wrote:
> > Hi Jing,
> >
> > On 08/16/2018 12:28 PM, Jing Liu wrote:
> > > Clean up the PCI config space of resource reserve capability.
> > >
> > > Signed-off-by: Jing Liu <address@hidden>
> > > ---
> > >   hw/pci/pci_bridge.c         | 9 +++++++++
> > >   include/hw/pci/pci_bridge.h | 1 +
> > >   2 files changed, 10 insertions(+)
> > >
> > > diff --git a/hw/pci/pci_bridge.c b/hw/pci/pci_bridge.c
> > > index 15b055e..dbcee90 100644
> > > --- a/hw/pci/pci_bridge.c
> > > +++ b/hw/pci/pci_bridge.c
> > > @@ -465,6 +465,15 @@ int pci_bridge_qemu_reserve_cap_init(PCIDevice 
> > > *dev, int cap_offset,
> > >       return 0;
> > >   }
> > > +void pci_bridge_qemu_reserve_cap_uninit(PCIDevice *dev)
> > > +{
> > > +    uint8_t pos = pci_find_capability(dev, PCI_CAP_ID_VNDR);
> > > +
> > > +    pci_del_capability(dev, PCI_CAP_ID_VNDR, 
> > > sizeof(PCIBridgeQemuCap));
> >
> > I think that you only need to call pci_del_capability,
> >
> > > +    memset(dev->config + pos + PCI_CAP_FLAGS, 0,
> > > +           sizeof(PCIBridgeQemuCap) - PCI_CAP_FLAGS);
> > > +}
> >
> > ... no need for the above line. The reason is pci_del_capability
> > will "unlink" the capability, and even if the data remains in
> > the configuration space array, it will not be used.
> I think I got it: pci_del_capability "unlink" by set the tag
> pdev->config[PCI_STATUS] &= ~PCI_STATUS_CAP_LIST;
> so that pdev->config will not be used, right?

If is the latest capability in the list, yes.
Otherwise it will simply link 'prev' with 'next' using config array offsets.

Thanks,
Marcel

> > Do you agree? If yes, just call pci_del_capability and you don't need
> > this patch.
> Yup, I agree with you. And let me remove this patch in next version.
>
> Thanks,
> Jing
>
> > Thanks,
> > Marcel
>
> [...]