PCI/LINK: Add Kconfig option (default off) (2078e1e7) · Commits · 戴 / test

("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: ("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>

drivers/pci/pcie/Kconfig

+8 −0

Original line number	Diff line number	Diff line
		@@ -142,3 +142,11 @@ config PCIE_PTM

		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.

drivers/pci/pcie/Makefile

+1 −1

Original line number	Diff line number	Diff line
		@@ -3,7 +3,6 @@
		# 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

		@@ -13,3 +12,4 @@ obj-$(CONFIG_PCIEAER_INJECT) += aer_inject.o
		obj-$(CONFIG_PCIE_PME) += pme.o
		obj-$(CONFIG_PCIE_DPC) += dpc.o
		obj-$(CONFIG_PCIE_PTM) += ptm.o
		obj-$(CONFIG_PCIE_BW) += bw_notification.o

drivers/pci/pcie/portdrv.h

+4 −0

Original line number	Diff line number	Diff line
		@@ -49,7 +49,11 @@ int pcie_dpc_init(void);
		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)

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