e8303bb7a75c ("PCI/LINK: Report degraded links via link bandwidth
notification") added dmesg logging whenever a link changes speed or width
to a state that is considered degraded. Unfortunately, it cannot
differentiate signal integrity-related link changes from those
intentionally initiated by an endpoint driver, including drivers that may
live in userspace or VMs when making use of vfio-pci. Some GPU drivers
actively manage the link state to save power, which generates a stream of
messages like this:
vfio-pci 0000:07:00.0: 32.000 Gb/s available PCIe bandwidth, limited by 2.5 GT/s x16 link at 0000:00:02.0 (capable of 64.000 Gb/s with 5 GT/s x16 link)
Since we can't distinguish the intentional changes from the signal
integrity issues, leave the reporting turned off by default. Add a Kconfig
option to turn it on if desired.
Fixes: e8303bb7a75c ("PCI/LINK: Report degraded links via link bandwidth notification")
Link: https://lore.kernel.org/linux-pci/20190501142942.26972-1-keith.busch@intel.com
Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
This is only useful if you have devices that support PTM, but it
is safe to enable even if you don't.
+
+config PCIE_BW
+ bool "PCI Express Bandwidth Change Notification"
+ depends on PCIEPORTBUS
+ help
+ This enables PCI Express Bandwidth Change Notification. If
+ you know link width or rate changes occur only to correct
+ unreliable links, you may answer Y.
# Makefile for PCI Express features and port driver
pcieportdrv-y := portdrv_core.o portdrv_pci.o err.o
-pcieportdrv-y += bw_notification.o
obj-$(CONFIG_PCIEPORTBUS) += pcieportdrv.o
obj-$(CONFIG_PCIE_PME) += pme.o
obj-$(CONFIG_PCIE_DPC) += dpc.o
obj-$(CONFIG_PCIE_PTM) += ptm.o
+obj-$(CONFIG_PCIE_BW) += bw_notification.o
static inline int pcie_dpc_init(void) { return 0; }
#endif
+#ifdef CONFIG_PCIE_BW
int pcie_bandwidth_notification_init(void);
+#else
+static inline int pcie_bandwidth_notification_init(void) { return 0; }
+#endif
/* Port Type */
#define PCIE_ANY_PORT (~0)