linux-kernel - [PATCH v3 06/21] x86/resctrl: Remove set_mba

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Date:   Thu, 17 Feb 2022 18:20:55 +0000
From:   James Morse <james.morse@....com>
To:     x86@...nel.org, linux-kernel@...r.kernel.org
Cc:     Fenghua Yu <fenghua.yu@...el.com>,
        Reinette Chatre <reinette.chatre@...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>,
        James Morse <james.morse@....com>,
        shameerali.kolothum.thodi@...wei.com,
        Jamie Iles <jamie@...iainc.com>,
        D Scott Phillips OS <scott@...amperecomputing.com>,
        lcherian@...vell.com, bobo.shaobowang@...wei.com,
        tan.shaopeng@...itsu.com
Subject: [PATCH v3 06/21] x86/resctrl: Remove set_mba_sc()s control array re-initialisation

set_mba_sc() enables the 'software controller' to regulate the
bandwidth based on the byte counters. This can be managed entirely
in the parts of resctrl that move to /fs/, without any extra
support from the architecture specific code.
set_mba_sc() is called by rdt_enable_ctx() during mount and
umount. It currently resets the arch code's ctrl_val[] and mbps_val[]
arrays.

The ctrl_val[] was already reset when the domain was created,
and by reset_all_ctrls() when the filesystem was last umounted.
Doing the work in set_mba_sc() is not necessary as the values are
already at their defaults due to the creation of the domain, or were
previsouly reset during umount(), or are about to reset during umount().

Add a reset of the mbps_val[] in reset_all_ctrls(), allowing the
code in set_mba_sc() that reaches in to the architecture specific
structures to be removed.

Signed-off-by: James Morse <james.morse@....com>

Changes since v2:
 * Moved earlier in the series, added the reset in reset_all_ctrls().
 * Rephrased commit message.
---
 arch/x86/kernel/cpu/resctrl/rdtgroup.c | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index 281b38b363c2..794a84ba9097 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -1898,18 +1898,12 @@ void rdt_domain_reconfigure_cdp(struct rdt_resource *r)
 static int set_mba_sc(bool mba_sc)
 {
 	struct rdt_resource *r = &rdt_resources_all[RDT_RESOURCE_MBA].r_resctrl;
-	struct rdt_hw_domain *hw_dom;
-	struct rdt_domain *d;
 
 	if (!is_mbm_enabled() || !is_mba_linear() ||
 	    mba_sc == is_mba_sc(r))
 		return -EINVAL;
 
 	r->membw.mba_sc = mba_sc;
-	list_for_each_entry(d, &r->domains, list) {
-		hw_dom = resctrl_to_arch_dom(d);
-		setup_default_ctrlval(r, hw_dom->ctrl_val, hw_dom->mbps_val);
-	}
 
 	return 0;
 }
@@ -2327,8 +2321,10 @@ static int reset_all_ctrls(struct rdt_resource *r)
 		hw_dom = resctrl_to_arch_dom(d);
 		cpumask_set_cpu(cpumask_any(&d->cpu_mask), cpu_mask);
 
-		for (i = 0; i < hw_res->num_closid; i++)
+		for (i = 0; i < hw_res->num_closid; i++) {
 			hw_dom->ctrl_val[i] = r->default_ctrl;
+			hw_dom->mbps_val[i] = MBA_MAX_MBPS;
+		}
 	}
 	cpu = get_cpu();
 	/* Update CBM on this cpu if it's in cpu_mask. */
-- 
2.30.2