linux-kernel - Re: [PATCH V2 0/6] Support PCIe3 uncore PMU on Snow Ridge

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Message-ID: <34e64852-0fe0-a1f2-d8a2-2356b3676619@linux.intel.com>
Date:   Mon, 31 Aug 2020 08:48:02 -0400
From:   "Liang, Kan" <kan.liang@...ux.intel.com>
To:     peterz@...radead.org, mingo@...hat.com,
        linux-kernel@...r.kernel.org
Cc:     bhelgaas@...gle.com, eranian@...gle.com, ak@...ux.intel.com
Subject: Re: [PATCH V2 0/6] Support PCIe3 uncore PMU on Snow Ridge

Hi Peter,

Could you please share the comments for this patch set?

Thanks,
Kan

On 8/5/2020 4:24 PM, kan.liang@...ux.intel.com wrote:
> From: Kan Liang <kan.liang@...ux.intel.com>
> 
> Changes since V1:
> - Drop the platform device solution
> - A new uncore PCI sub driver solution is introduced which searches
>    the PCIe Root Port device via pci_get_device() and id table.
>    Register a PCI bus notifier for the remove notification. Once the
>    device is removed, the uncore driver can be notified to unregister
>    the corresponding PMU.
> - Modify the parameters of uncore_pci_pmu_unregister() function.
> 
> The Snow Ridge integrated PCIe3 uncore performance monitoring unit (PMU)
> can be used to collect the performance data, e.g., the utilization
> between the PCIe devices and the components (in M2IOSF) which are
> responsible for translating and managing the requests to/from the
> device. The performance data is very useful for analyzing the
> performance of the PCIe devices.
> 
> The PCIe3 uncore PMU was once supported in the Linux kernel, but it was
> removed by the commit 2167f1625c2f ("perf/x86/intel/uncore: Remove
> PCIe3 unit for SNR") due to the conflict between the PCIe Root Port
> driver and the perf uncore driver. The counters of the PCIe3 uncore PMU
> are located in the configuration space of the PCIe Root Port device,
> which already has a bonded driver portdrv_pci. One device can only have
> one bonded driver. The uncore driver is always failed to be loaded.
> 
> To re-enable the PCIe3 uncore PMU support in the uncore driver, a new
> solution should be introduced, which has to meet the requirements as
> below:
> - must have a reliable way to find the PCIe Root Port device from the
>    uncore driver;
> - must be able to access the uncore counters of the PCIe Root Port
>    device from the uncore driver;
> - must support hotplug. When the PCIe Root Port device is removed, the
>    uncore driver has to be notified and unregisters the PCIe3 uncore
>    PMU.
> 
> In the v1 patch set, a new platform device solution is implemented to
> address the issue, but it's rejected.
> https://lkml.kernel.org/r/20200708183034.GA466341@bjorn-Precision-5520
> 
> A new uncore PCI sub driver solution is introduced from the V2 patch
> set, which:
> - searches the PCIe Root Port device via pci_get_device() and id table.
>    The matched pci_dev can be used to register a PMU for accessing the
>    counters in the PCIe Root Port device.
> - register a PCI bus notifier. Once the device is removed, the uncore
>    driver can be notified to unregister the corresponding PMU.
> 
> Kan Liang (6):
>    perf/x86/intel/uncore: Factor out uncore_pci_get_dev_die_info()
>    perf/x86/intel/uncore: Factor out uncore_pci_find_dev_pmu()
>    perf/x86/intel/uncore: Factor out uncore_pci_pmu_register()
>    perf/x86/intel/uncore: Factor out uncore_pci_pmu_unregister()
>    perf/x86/intel/uncore: Generic support for the PCI sub driver
>    perf/x86/intel/uncore: Support PCIe3 unit on Snow Ridge
> 
>   arch/x86/events/intel/uncore.c       | 273 +++++++++++++++++++++++++++--------
>   arch/x86/events/intel/uncore.h       |   1 +
>   arch/x86/events/intel/uncore_snbep.c |  53 +++++++
>   3 files changed, 265 insertions(+), 62 deletions(-)
>