linux-kernel - Re: [PATCH v2 05/13] platform/x86: hfi: Introduce AMD Hardware Feedback Interface Driver

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Message-ID: <20241015035233.GA28522@ranerica-svr.sc.intel.com>
Date: Mon, 14 Oct 2024 20:52:33 -0700
From: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
To: Mario Limonciello <mario.limonciello@....com>
Cc: Borislav Petkov <bp@...en8.de>, Hans de Goede <hdegoede@...hat.com>,
	Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
	x86@...nel.org, "Gautham R . Shenoy" <gautham.shenoy@....com>,
	Perry Yuan <perry.yuan@....com>, linux-kernel@...r.kernel.org,
	linux-doc@...r.kernel.org, linux-pm@...r.kernel.org,
	platform-driver-x86@...r.kernel.org,
	Shyam Sundar S K <Shyam-sundar.S-k@....com>
Subject: Re: [PATCH v2 05/13] platform/x86: hfi: Introduce AMD Hardware
 Feedback Interface Driver

On Thu, Oct 10, 2024 at 02:36:57PM -0500, Mario Limonciello wrote:
> From: Perry Yuan <Perry.Yuan@....com>
> 
> The AMD Heterogeneous core design and Hardware Feedback Interface (HFI)
> provide behavioral classification and a dynamically updated ranking table
> for the scheduler to use when choosing cores for tasks.
> 
> There are two CPU core types defined: `Classic Core` and `Dense Core`.
> "Classic" cores are the standard performance cores, while "Dense" cores
> are optimized for area and efficiency.
> 
> Heterogeneous compute refers to CPU implementations that are comprised
> of more than one architectural class, each with two capabilities. This
> means each CPU reports two separate capabilities: "perf" and "eff".
> 
> Each capability lists all core ranking numbers between 0 and 255, where
> a higher number represents a higher capability.
> 
> Heterogeneous systems can also extend to more than two architectural
> classes.
> 
> The purpose of the scheduling feedback mechanism is to provide information
> to the operating system scheduler in real time, allowing the scheduler to
> direct threads to the optimal core during task scheduling.
> 
> All core ranking data are provided by the BIOS via a shared memory ranking
> table, which the driver reads and uses to update core capabilities to the
> scheduler. When the hardware updates the table, it generates a platform
> interrupt to notify the OS to read the new ranking table.
> 
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=206537

I tried to find the HFI details on the documents in this "bug" but I could
not find them. What document in specific could I look at?

Thanks and BR,
Ricardo