When assigning a physical PCIe device to a QEMU/KVM guest, PciBusDxe may
find that the extended config space is not (fully) implemented. In
LocatePciExpressCapabilityRegBlock(), "CapabilityEntry" may be read as
0xFFFF_FFFF at a given config space offset, after which the loop gets
stuck spinning on offset 0xFFC (the read at offset 0xFFC returns
0xFFFF_FFFF most likely as well).
Another scenario (not related to virtualization) for triggering the above
is when a Conventional PCI bus -- exposed by a PCIe-to-PCI bridge in the
topology -- intervenes between a PCI Express Root Port and a PCI Express
Endpoint. The Conventional PCI bus limits the accessible config space of
the PCI Express Endpoint, even though the endpoint advertizes the PCI
Express capability. Here's a diagram, courtesy of Alex Williamson:
[PCIe Root Port]--[PCIe-to-PCI]--[PCI-to-PCIe]--[PCIe EP]
->| |<- Conventional PCI bus
Catch reads of 0xFFFF_FFFF in LocatePciExpressCapabilityRegBlock(), and
break out of the scan with a warning message. The function will return
EFI_NOT_FOUND.
Cc: Alex Williamson <alex.williamson@redhat.com>
Cc: Hao A Wu <hao.a.wu@intel.com>
Cc: Jian J Wang <jian.j.wang@intel.com>
Cc: Ray Ni <ray.ni@intel.com>
Cc: Star Zeng <star.zeng@intel.com>
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Philippe Mathieu-Daude <philmd@redhat.com>
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Acked-by: Hao A Wu <hao.a.wu@intel.com>
Reviewed-by: Ray Ni <ray.ni@intel.com>
+ if (CapabilityEntry == MAX_UINT32) {\r
+ DEBUG ((\r
+ DEBUG_WARN,\r
+ "%a: [%02x|%02x|%02x] failed to access config space at offset 0x%x\n",\r
+ __FUNCTION__,\r
+ PciIoDevice->BusNumber,\r
+ PciIoDevice->DeviceNumber,\r
+ PciIoDevice->FunctionNumber,\r
+ CapabilityPtr\r
+ ));\r
+ break;\r
+ }\r
+\r
CapabilityID = (UINT16) CapabilityEntry;\r
\r
if (CapabilityID == CapId) {\r
CapabilityID = (UINT16) CapabilityEntry;\r
\r
if (CapabilityID == CapId) {\r