Debugging a WIP PCI/ACPI patch: Bad tailq NEXT(0xffffffff81cde660->tqh_last) != NULL

[Neel Chauhan]

Hi Doug,

Thank you so much for this information.

On 2020-12-31 12:07, Doug Ambrisko wrote:
> FYI, looks like this needs to be ported over from Linux:
> static char __iomem *vmd_cfg_addr(struct vmd_dev *vmd, struct pci_bus 
> *bus,
>                                   unsigned int devfn, int reg, int len)
> {
>         char __iomem *addr = vmd->cfgbar +
>                              ((bus->number - vmd->busn_start) << 20) +
>                              (devfn << 12) + reg;
> 
> to
> vmd_read_config
>         offset = (b << 20) + (s << 15) + (f << 12) + reg;
> 
> vmd_write_config(device_t dev, u_int b, u_int s, u_int f, u_int reg,
>         offset = (b << 20) + (s << 15) + (f << 12) + reg;
> 
> ie.
> 	offset = ((b - sc->vmd_bus_start) << 20) + (s << 15) + (f << 12) + 
> reg;
> 
> vmd_bus_start should be added to the softc as a uint8_t type and needs 
> to
> be set via attach.  We need range checks to make sure
> vmd_write_config/vmd_read_config doesn't read something out of range
> since it has been reduced.

One thing I noticed is that the "b" variable (which corresponds to the 
Linux bus->number) is 0 (thanks to printf). This should be the bus 
number if we want to attach.

If I use: "b = pci_get_bus(dev);" in the attach, b is still 0.

And that leads to a kernel panic.

> Not sure what the shadow registers do.  These both seem to be new Intel
> features and Intel doc's have been minimal.  Looks like Intel is doing
> a sparse map now on newer devices.

I guess Linux is our best hope. Unless the new Intel docs is the Linux 
kernel source.

> I'm concerned about the Linux comment of:
>          * Certain VMD devices may have a root port configuration 
> option which
>          * limits the bus range to between 0-127, 128-255, or 224-255
> 
> since I don't see anything to limit it between 0-127 only starting
> at 0, 128 or 224,  Maybe there is max of 128 busses overall?

I could be wrong, but I guess that's a typo.

> I don't have this type of HW to test things.

I can use my hardware for testing. In the worse case scenario, I can 
donate an entry-level 11th Gen/TigerLake system if I have the funds 
and/or can get a tax credit.

> Doug A.

-Neel