linux-kernel - Re: [PATCH v5 0/2] x86/resctrl: Pass domain to target CPU

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Date: Thu, 28 Mar 2024 21:55:21 -0700
From: Reinette Chatre <reinette.chatre@...el.com>
To: Borislav Petkov <bp@...en8.de>
CC: Thomas Gleixner <tglx@...utronix.de>, <x86@...nel.org>,
	<linux-kernel@...r.kernel.org>, "Yu, Fenghua" <fenghua.yu@...el.com>, "Ingo
 Molnar" <mingo@...hat.com>, 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>, James Morse <james.morse@....com>, Tony
 Luck <tony.luck@...el.com>
Subject: Re: [PATCH v5 0/2] x86/resctrl: Pass domain to target CPU

Hi Boris,

Could you please consider this series for inclusion?

Thank you very much.

Reinette

On 3/8/2024 1:38 PM, Tony Luck wrote:
> reset_all_ctrls() and resctrl_arch_update_domains() use on_each_cpu_mask()
> to call rdt_ctrl_update() on potentially one CPU from each domain.
> 
> But this means rdt_ctrl_update() needs to figure out which domain to
> apply changes to. Doing so requires a search of all domains in a resource,
> which can only be done safely if cpus_lock is held. Both callers do hold
> this lock, but there isn't a way for a function called on another CPU
> via IPI to verify this.
> 
> Commit c0d848fcb09d ("x86/resctrl: Remove lockdep annotation that triggers
> false positive") removed the incorrect assertions.
> 
> Add the target domain to the msr_param structure and
> call rdt_ctrl_update() for each domain separately using
> smp_call_function_single(). This means that rdt_ctrl_update() doesn't
> need to search for the domain and get_domain_from_cpu() can safely assert
> that the cpus_lock is held since the remaining callers do not use IPI.
> 
> Signed-off-by: Tony Luck <tony.luck@...el.com>
> 
> ---
> Changes since V4: Link: https://lore.kernel.org/all/20240228193717.8170-1-tony.luck@intel.com/
> 
> Reinette: Only assign "cpu" once in resctrl_arch_update_domains() [but
> see change from James below]
> 
> James: Use smp_call_function_any() instead of cpumask_any() +
> smp_call_function_single() to avoid unnecessary IPI in both
> resctrl_arch_update_domains() and reset_all_ctrls(). This
> eliminates a need for the "cpu" local variable.
> 
> Tony Luck (2):
>   x86/resctrl: Pass domain to target CPU
>   x86/resctrl: Simplify call convention for MSR update functions
> 
>  arch/x86/kernel/cpu/resctrl/internal.h    |  5 ++-
>  arch/x86/kernel/cpu/resctrl/core.c        | 55 +++++++++--------------
>  arch/x86/kernel/cpu/resctrl/ctrlmondata.c | 40 ++++-------------
>  arch/x86/kernel/cpu/resctrl/rdtgroup.c    | 12 +----
>  4 files changed, 34 insertions(+), 78 deletions(-)
> 
> 
> base-commit: c0d848fcb09d80a5f48b99f85e448185125ef59f