i386/180599: PCIe chipset test is not valid on recent Intel platforms

[Chris Main]

>Number:         180599
>Category:       i386
>Synopsis:       PCIe chipset test is not valid on recent Intel platforms
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-i386
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Tue Jul 16 19:10:00 UTC 2013
>Closed-Date:
>Last-Modified:
>Originator:     Chris Main
>Release:        9.1
>Organization:
TenAsys
>Environment:
(various)
>Description:
It is not possible to set up MSI interrupts on devices which appear before a PCI Express root complex on Intel series 7/series 8 chipsets because the pci_msi_blacklisted() test fails (in dev/pci.c)
The reason is that the method for setting the pcie_chipset variable is no longer valid. Most devices in a PCI Express system no longer have the PCI Express capability registers, unless they are PCI Express root complexes or PCI Express plug-in cards. 

An example is the XHCI controller in the 7-series chipset, which occurs at pci0:0:20:0 and has no PCI Express capability register, but is MSI-capable. Because none of the preceding devices have the PCI Express capability either, the MSI test fails. 
>How-To-Repeat:
Boot FreeBSD on such a system and use pciconf to demonstrate that the XHCI has been set up with an IRQ and not MSI. 
>Fix:
Need a different method to determine system PCI Express property 

>Release-Note:
>Audit-Trail:
>Unformatted: