Re: perf/x86/intel/uncore: propose to support IIO free-running counters in 4.14

[Greg KH <gregkh@linuxfoundation.org>]

On Tue, Aug 28, 2018 at 11:11:02AM +0800, Jin, Yao wrote:
> Hi,
> 
> The upstream kernel has supported IIO free-running counters on Skylake
> server. As of Skylake Server, there are a number of free running counters in
> each IIO Box that collect counts of per-box IO clocks and per-port
> Input/Output x BW/Utilization.
> 
> There are three types of IIO free-running counters on Skylake server:
> 
> 1. IO CLOCKS counter: a clock of IIO box.
> 
> 2. BANDWIDTH counters: count inbound(PCIe->CPU)/outbound(CPU->PCIe)
> bandwidth.
> 
> 3. UTILIZATION counters: count input/output utilization.
> 
> With these IIO free-running counters, we can get good observation for IIO
> traffic on Skylake server. For example, we can see the IIO inbound bandwidth
> (PCIe->CPU).
> 
> root@skx /sys/devices# perf stat -a -e
> uncore_iio_free_running_2/bw_in_port0/
> ^C
>  Performance counter stats for 'system wide':
> 
>             153.19 MiB  uncore_iio_free_running_2/bw_in_port0/
> 
>        8.037701069 seconds time elapsed
> 
> I propose to backport the patches which support IIO free-running counters to
> 4.14 stable kernel.
> 
> perf/x86/intel/uncore: Introduce customized event_read() for client IMC
> uncore
> 2da331465f44f9618abe8837d1a68405d550b66e
> 
> perf/x86/intel/uncore: Add new data structures for free running counters
> 927b2deb067b8b4753fc09c7a42092f43fc0c1f6
> 
> perf/x86/intel/uncore: Add infrastructure for free running counters
> 0e0162dfcd1fbe4c711ee86f24f966c318999603
> 
> perf/x86/intel/uncore: Support IIO free-running counters on SKX
> 0f519f0352e37e7d71bdce5559517c74a35f6e33
> 
> perf/x86/intel/uncore: Expose uncore_pmu_event*() functions
> 5a6c9d94e9ed7410142bc6fcb638a4db1895aa0c
> 
> perf/x86/intel/uncore: Clean up client IMC uncore
> 9aae1780e7e81e54edfb70ba33ead5b0b48be009

Where in the stable kernel rules does it say that these types of patches
are ok to be backported?

Why not just use a newer kernel release if you want to use these new
features?  What is preventing these users from using 4.18 or newer?

thanks,

greg k-h