linux-kernel - Re: [PATCH v1 1/6] x86/resctrl: Move __resctrl_sched

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Date: Mon, 8 Apr 2024 13:59:23 -0700
From: Reinette Chatre <reinette.chatre@...el.com>
To: Peter Newman <peternewman@...gle.com>
CC: Fenghua Yu <fenghua.yu@...el.com>, James Morse <james.morse@....com>,
	Stephane Eranian <eranian@...gle.com>, Thomas Gleixner <tglx@...utronix.de>,
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	<dave.hansen@...ux.intel.com>, <x86@...nel.org>, "H. Peter Anvin"
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	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1 1/6] x86/resctrl: Move __resctrl_sched_in() out-of-line

Hi Peter,

On 4/8/2024 12:05 PM, Peter Newman wrote:
> Hi Reinette,
> 
> On Sun, Apr 7, 2024 at 12:21 PM Reinette Chatre
> <reinette.chatre@...el.com> wrote:
>>
>> I think this needs more thought. rdt_enable_key is x86 specific now and should not
>> be in the fs code. Every architecture will have its own task switch code, with
>> __resctrl_sched_in() belonging to x86 and thus not something to be directly called
>> from the fs code.
> 
> I think we will need to discuss whether __resctrl_sched_in() is really
> arch or FS code following the changes in this series. This series
> removes the explicit MSR access and James has already provided inline

Indeed, I missed how resctrl_arch_update_cpu() introduced in
"x86/resctrl: Abstract PQR_ASSOC from generic code" results in
__resctrl_sched_in() being architecture agnostic.

(sidenotes ...  it is not obvious to me why resctrl_arch_update_cpu()
is not consistently used, for example, in clear_closid_rmid(),
and it also seems a better candidate to be inline within
arch/x86/include/asm/resctrl.h)

> wrappers for the mon and alloc enable keys[1], so I can only assume
> they are architecture-independent in concept.

The wrappers are intended to be architecture-independent, but the keys
are architecture dependent. Quoting the commit you linked to:
"This means other architectures don't have to mirror the static keys"

Reinette
 
> https://lore.kernel.org/r/20240213184438.16675-18-james.morse@arm.com