Re: [PATCH v6 07/16] x86/pci: Add Hygon Dhyana support to PCI and north bridge

[Pu Wen]

On 2018/9/20 1:20, Lendacky, Thomas wrote:
> > @@ -197,12 +212,25 @@ int amd_cache_northbridges(void)
> >   	u16 i = 0;
> >   	struct amd_northbridge *nb;
> >   	struct pci_dev *root, *misc, *link;
> > +	const struct pci_device_id *root_ids = NULL;
> > +	const struct pci_device_id *misc_ids = NULL;
> > +	const struct pci_device_id *link_ids = NULL;
> > +
> > +	if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD) {
> > +		root_ids = amd_root_ids;
> > +		misc_ids = amd_nb_misc_ids;
> > +		link_ids = amd_nb_link_ids;
> > +	} else if (boot_cpu_data.x86_vendor == X86_VENDOR_HYGON) {
> > +		root_ids = hygon_root_ids;
> > +		misc_ids = hygon_nb_misc_ids;
> > +		link_ids = hygon_nb_link_ids;
> > +	}
>
> To be compatible with "before this patch" you should probably do:
>
> 	if (boot_cpu_data.x86_vendor == X86_VENDOR_HYGON) {
> 		root_ids = hygon_root_ids;
> 		misc_ids = hygon_nb_misc_ids;
> 		link_ids = hygon_nb_link_ids;
> 	} else {
> 		root_ids = amd_root_ids;
> 		misc_ids = amd_nb_misc_ids;
> 		link_ids = amd_nb_link_ids;
> 	}
>
> That way they are always the AMD values if not your chip.
...
> > @@ -263,9 +291,15 @@ bool __init early_is_amd_nb(u32 device)
> >   {
> >   	const struct pci_device_id *id;
> >   	u32 vendor = device & 0xffff;
> > +	const struct pci_device_id *misc_ids = NULL;
> > +
> > +	if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD)
> > +		misc_ids = amd_nb_misc_ids;
> > +	else if (boot_cpu_data.x86_vendor == X86_VENDOR_HYGON)
> > +		misc_ids = hygon_nb_misc_ids;
>
> Same comment as above.  This will probably eliminate the PANIC that
> that was reported by LKP.

Yes, it's this modification that caused the PANIC reported by LKP.
Because the misc_ids will be NULL if running on Intel chip.

If change the vendor checking like this:

+	if (boot_cpu_data.x86_vendor == X86_VENDOR_HYGON)
+		misc_ids = hygon_nb_misc_ids;
+	else
+		misc_ids = amd_nb_misc_ids;

The PANIC will be eliminated.

The PANIC will also be eliminated by adding AMD vendor checking in
amd_gart_present:

+	if(boot_cpu_data.x86_vendor != X86_VENDOR_AMD)
+		return false;

To prevent the function return true on non AMD platform.

Thanks,
Pu Wen