linux-kernel - Re: [PATCH v3 13/38] x86/resctrl: Move resctrl types to a separate header

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Date: Fri, 28 Jun 2024 09:45:55 -0700
From: Reinette Chatre <reinette.chatre@...el.com>
To: James Morse <james.morse@....com>, <x86@...nel.org>,
	<linux-kernel@...r.kernel.org>
CC: Fenghua Yu <fenghua.yu@...el.com>, Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, H Peter Anvin
	<hpa@...or.com>, Babu Moger <Babu.Moger@....com>,
	<shameerali.kolothum.thodi@...wei.com>, D Scott Phillips OS
	<scott@...amperecomputing.com>, <carl@...amperecomputing.com>,
	<lcherian@...vell.com>, <bobo.shaobowang@...wei.com>,
	<tan.shaopeng@...itsu.com>, <baolin.wang@...ux.alibaba.com>, Jamie Iles
	<quic_jiles@...cinc.com>, Xin Hao <xhao@...ux.alibaba.com>,
	<peternewman@...gle.com>, <dfustini@...libre.com>, <amitsinght@...vell.com>,
	David Hildenbrand <david@...hat.com>, Rex Nie <rex.nie@...uarmicro.com>,
	"Dave Martin" <dave.martin@....com>, Shaopeng Tan
	<tan.shaopeng@...fujitsu.com>
Subject: Re: [PATCH v3 13/38] x86/resctrl: Move resctrl types to a separate
 header

Hi James,

On 6/14/24 8:00 AM, James Morse wrote:
> When resctrl is fully factored into core and per-arch code, each arch
> will need to use some resctrl common definitions in order to define its
> own specializations and helpers.  Following conventional practice, it
> would be desirable to put the dependent arch definitions in an
> <asm/resctrl.h> header that is included by the common <linux/resctrl.h>
> header.  However, this can make it awkward to avoid a circular
> dependency between <linux/resctrl.h> and the arch header.
> 
> To avoid such dependencies, move the affected common types and
> constants into a new header that does not need to depend on
> <linux/resctrl.h> or on the arch headers.
> 
> The same logic applies to the monitor-configuration defines, move these
> too.
> 
> Some kind of enumeration for events is needed between the filesystem
> and architecture code. Take the x86 definition as its convenient for
> x86.
> 
> The definition of enum resctrl_event_id is need to allow the architecture

"is need" -> "is needed" ?

> code to define resctrl_arch_event_is_free_running(),

Cannot find resctrl_arch_event_is_free_running()

> resctrl_arch_set_cdp_enabled(), resctrl_arch_mon_ctx_alloc() and

resctrl_arch_set_cdp_enabled() should not need enum resctrl_event_id


> resctrl_arch_mon_ctx_free().
> 
> The definition of enum resctrl_res_level is needed to allow the
> architecture code to define resctrl_arch_set_cdp_enabled() and
> resctrl_arch_get_cdp_enabled().
> 
> The bits for mbm_local_bytes_config et al are ABI, and must be the same
> on all architectures. These are documented in
> Documentation/arch/x86/resctrl.rst
> 
> The maintainers entry for these headers was missed when resctrl.h was
> created. Add a wildcard entry to match both resctrl.h and
> resctrl_types.h.
> 
> Signed-off-by: James Morse <james.morse@....com>
> Tested-by: Peter Newman <peternewman@...gle.com>
> Tested-by: Shaopeng Tan <tan.shaopeng@...fujitsu.com>
> ---
> Changes since v2:
>   * Added to the commit message why each of these things is necessary.
>   * Moved the enum resctrl_conf_type back to resctrl.h - this week arm's
>     CDP emulation code gets away without this...
> 
> Changes since v1:
>   * [Commit message only] Rewrite commit message to clarify the the
>     rationale for refactoring the headers in this way.
> ---
>   MAINTAINERS                            |  1 +
>   arch/x86/kernel/cpu/resctrl/internal.h | 24 ------------
>   include/linux/resctrl.h                | 21 +---------
>   include/linux/resctrl_types.h          | 54 ++++++++++++++++++++++++++

Considering the motivation I also expected to see a change in
arch/x86/include/asm/resctrl.h that adds the #include of the new file.

Reinette