Re: [PATCH v2 2/2] hw/smbios: retrieve PCI address from specified device for Type 41

[Michael S. Tsirkin]

On Thu, Apr 01, 2021 at 04:26:50PM +0200, Vincent Bernat wrote:
>  ❦  1 avril 2021 09:59 -04, Michael S. Tsirkin:
> 
> >> +                /*
> >> +                 * TODO: Extract the appropriate value. Most of the
> >> +                 * time, this will be 0.
> >> +                 */
> >> +                t->segment_group_number = cpu_to_le16(0);
> >> +                t->bus_number = pci_dev_bus_num(pdev);
> >> +                t->device_number = pdev->devfn;
> >
> > Problem is, for devices behind bridges for example, bus is only
> > configured by guest, after pci has been enumerated.
> >
> > So I suspect this either
> > - needs to be limited to only work for the root bus
> > - needs to be re-evaluted on guest access, like we do
> >   with ACPI
> 
> Or the address can be provided by the user. I didn't want to keep that
> at this is error prone and there may be surprises after adding a device
> or after a QEMU upgrade.

Or on guest changes.

> 
> Otherwise, limiting to the root bus seems a fine limitation by me. How
> do I check that?

pci_bus_is_root will do this. Pls document the reason for the
limitation.


> -- 
> Don't just echo the code with comments - make every comment count.
>             - The Elements of Programming Style (Kernighan & Plauger)