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

[Neel Chauhan]

Just to ping you in case you may have missed my reply (I understand, New 
Years Day).

Is there a reason why "b = pci_get_bus(dev);" return 0 even when the bus 
number is shifted (as it is on Linux)?

-Neel

On 2020-12-31 21:49, Neel Chauhan wrote:
> 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
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