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

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Message-ID: <20240308213846.77075-1-tony.luck@intel.com>
Date: Fri,  8 Mar 2024 13:38:44 -0800
From: Tony Luck <tony.luck@...el.com>
To: "Chatre, Reinette" <reinette.chatre@...el.com>,
	Borislav Petkov <bp@...en8.de>,
	James Morse <james.morse@....com>
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>,
	Tony Luck <tony.luck@...el.com>
Subject: [PATCH v5 0/2] x86/resctrl: Pass domain to target CPU

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
-- 
2.43.0