Re: [PATCHv2] PCI/LINK: Add Kconfig option (default off)

[Bjorn Helgaas <helgaas@kernel.org>]

On Wed, May 01, 2019 at 08:29:42AM -0600, Keith Busch wrote:
> 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")
> Signed-off-by: Keith Busch <keith.busch@intel.com>

Applied to for-linus for v5.1, thanks!

> ---
>  drivers/pci/pcie/Kconfig   | 8 ++++++++
>  drivers/pci/pcie/Makefile  | 2 +-
>  drivers/pci/pcie/portdrv.h | 4 ++++
>  3 files changed, 13 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/pcie/Kconfig b/drivers/pci/pcie/Kconfig
> index 5cbdbca904ac..a70efdffe647 100644
> --- a/drivers/pci/pcie/Kconfig
> +++ b/drivers/pci/pcie/Kconfig
> @@ -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.
> diff --git a/drivers/pci/pcie/Makefile b/drivers/pci/pcie/Makefile
> index f1d7bc1e5efa..efb9d2e71e9e 100644
> --- a/drivers/pci/pcie/Makefile
> +++ b/drivers/pci/pcie/Makefile
> @@ -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
> diff --git a/drivers/pci/pcie/portdrv.h b/drivers/pci/pcie/portdrv.h
> index 1d50dc58ac40..944827a8c7d3 100644
> --- a/drivers/pci/pcie/portdrv.h
> +++ b/drivers/pci/pcie/portdrv.h
> @@ -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)
> -- 
> 2.14.4
>