Re: [PATCH v2 2/2] PCI: vmd: Issue vmd domain window reset

[Bjorn Helgaas <helgaas@kernel.org>]

On Thu, Jul 22, 2021 at 11:47:06AM -0700, Patel, Nirmal wrote:
> On 7/20/2021 3:42 PM, Bjorn Helgaas wrote:
> > On Tue, Jul 20, 2021 at 01:50:09PM -0700, Nirmal Patel wrote:
> >> In order to properly re-initialize the VMD domain during repetitive driver
> >> attachment or reboot tests, ensure that the VMD root ports are re-initialized
> >> to a blank state that can be re-enumerated appropriately by the PCI core.
> >> This is performed by re-initializing all of the bridge windows to ensure
> >> that PCI core enumeration does not detect potentially invalid bridge windows
> >> and misinterpret them as firmware-assigned windows, when they simply may be
> >> invalid bridge window information from a previous boot.

> >> +static void vmd_domain_reset_windows(struct vmd_dev *vmd)
> >> +{
> >> +	u8 hdr_type;
> >> +	char __iomem *addr;
> >> +	int dev_seq;
> >> +	u8 functions;
> >> +	u8 fn_seq;
> >> +	int max_devs = resource_size(&vmd->resources[0]) * 32;
> >> +
> >> +	for (dev_seq = 0; dev_seq < max_devs; dev_seq++) {
> >> +		addr = VMD_DEVICE_BASE(vmd, dev_seq) + PCI_VENDOR_ID;
> >> +		if (readw(addr) != PCI_VENDOR_ID_INTEL)
> >> +			continue;
> >> +
> >> +		addr = VMD_DEVICE_BASE(vmd, dev_seq) + PCI_HEADER_TYPE;
> >> +		hdr_type = readb(addr) & PCI_HEADER_TYPE_MASK;
> >> +		if (hdr_type != PCI_HEADER_TYPE_BRIDGE)
> >> +			continue;
> >> +
> >> +		functions = !!(hdr_type & 0x80) ? 8 : 1;
> >> +		for (fn_seq = 0; fn_seq < functions; fn_seq++)
> >> +		{
> >
> > Looks quite parallel to vmd_domain_sbr(), except that here we iterate
> > through functions as well.  Why does vmd_domain_sbr() not need to
> > iterate through functions?
>
> I am not sure if there is VMD hardware with non zero functions.

I'm not sure either ;)  Hopefully you can resolve this one way or the
other.  It would be good to either make them the same or add a comment
about why they are different.  Otherwise it just looks like a possible
bug.