linux-kernel - Re: [PATCH V9 0/5] Intel Platform Monitoring Technology

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Date:   Thu, 29 Oct 2020 15:16:33 +0000
From:   Lee Jones <lee.jones@...aro.org>
To:     "David E. Box" <david.e.box@...ux.intel.com>
Cc:     hdegoede@...hat.com, mgross@...ux.intel.com, bhelgaas@...gle.com,
        alexey.budankov@...ux.intel.com, linux-kernel@...r.kernel.org,
        platform-driver-x86@...r.kernel.org, linux-pci@...r.kernel.org
Subject: Re: [PATCH V9 0/5] Intel Platform Monitoring Technology

On Wed, 28 Oct 2020, David E. Box wrote:

> Intel Platform Monitoring Technology (PMT) is an architecture for
> enumerating and accessing hardware monitoring capabilities on a device.
> With customers increasingly asking for hardware telemetry, engineers not
> only have to figure out how to measure and collect data, but also how to
> deliver it and make it discoverable. The latter may be through some device
> specific method requiring device specific tools to collect the data. This
> in turn requires customers to manage a suite of different tools in order to
> collect the differing assortment of monitoring data on their systems.  Even
> when such information can be provided in kernel drivers, they may require
> constant maintenance to update register mappings as they change with
> firmware updates and new versions of hardware. PMT provides a solution for
> discovering and reading telemetry from a device through a hardware agnostic
> framework that allows for updates to systems without requiring patches to
> the kernel or software tools.
> 
> PMT defines several capabilities to support collecting monitoring data from
> hardware. All are discoverable as separate instances of the PCIE Designated
> Vendor extended capability (DVSEC) with the Intel vendor code. The DVSEC ID
> field uniquely identifies the capability. Each DVSEC also provides a BAR
> offset to a header that defines capability-specific attributes, including
> GUID, feature type, offset and length, as well as configuration settings
> where applicable. The GUID uniquely identifies the register space of any
> monitor data exposed by the capability. The GUID is associated with an XML
> file from the vendor that describes the mapping of the register space along
> with properties of the monitor data. This allows vendors to perform
> firmware updates that can change the mapping (e.g. add new metrics) without
> requiring any changes to drivers or software tools. The new mapping is
> confirmed by an updated GUID, read from the hardware, which software uses
> with a new XML.
> 
> The current capabilities defined by PMT are Telemetry, Watcher, and
> Crashlog.  The Telemetry capability provides access to a continuous block
> of read only data. The Watcher capability provides access to hardware
> sampling and tracing features. Crashlog provides access to device crash
> dumps.  While there is some relationship between capabilities (Watcher can
> be configured to sample from the Telemetry data set) each exists as stand
> alone features with no dependency on any other. The design therefore splits
> them into individual, capability specific drivers. MFD is used to create
> platform devices for each capability so that they may be managed by their
> own driver. The PMT architecture is (for the most part) agnostic to the
> type of device it can collect from. Software can determine which devices
> support a PMT feature by searching through each device node entry in the
> sysfs class folder. It can additionally determine if a particular device
> supports a PMT feature by checking for a PMT class folder in the device
> folder.
> 
> This patch set provides support for the PMT framework, along with support
> for Telemetry on Tiger Lake.
> 
> Changes from V8:
>  	- Rebase on 5.10-rc1
> 	- Add missing changes in MFD patch from V7 that were accidentally
> 	  dropped in V8

Which changes are those?

Do I need to re-review?

> 	- Remove error message when unsupported capability found. Avoids
> 	  unnecessary noise on some systems.

-- 
Lee Jones [李琼斯]
Senior Technical Lead - Developer Services
Linaro.org │ Open source software for Arm SoCs
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