linux-kernel - [PATCH v2] x86/resctrl: Don't stop walking closids when a locksetup group is found

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Message-Id: <20190603172531.178830-1-james.morse@arm.com>
Date:   Mon,  3 Jun 2019 18:25:31 +0100
From:   James Morse <james.morse@....com>
To:     linux-kernel@...r.kernel.org, x86@...nel.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 Avin <hpa@...or.com>, james.morse@....com
Subject: [PATCH v2] x86/resctrl: Don't stop walking closids when a locksetup group is found

When a new control group is created __init_one_rdt_domain() walks all
the other closids to calculate the sets of used and unused bits.

If it discovers a pseudo_locksetup group, it breaks out of the loop.
This means any later closid doesn't get its used bits added to used_b.
These bits will then get set in unused_b, and added to the new
control group's configuration, even if they were marked as exclusive
for a later closid.

When encountering a pseudo_locksetup group, we should continue. This
is because "a resource group enters 'pseudo-locked' mode after the
schemata is written while the resource group is in 'pseudo-locksetup'
mode." When we find a pseudo_locksetup group, its configuration is
expected to be overwritten, we can skip it.

Fixes: dfe9674b04ff6 ("x86/intel_rdt: Enable entering of pseudo-locksetup mode")
Cc: <stable@...r.kernel.org>
Acked-by: Reinette Chatre <reinette.chatre@...el.com>
Signed-off-by: James Morse <james.morse@....com>
---
Changes since v1:
 * Removed braces round multi-line comment and whitespace after the if() block

 arch/x86/kernel/cpu/resctrl/rdtgroup.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index 333c177a2471..869cbef5da81 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -2542,7 +2542,12 @@ static int __init_one_rdt_domain(struct rdt_domain *d, struct rdt_resource *r,
 		if (closid_allocated(i) && i != closid) {
 			mode = rdtgroup_mode_by_closid(i);
 			if (mode == RDT_MODE_PSEUDO_LOCKSETUP)
-				break;
+				/*
+				 * ctrl values for locksetup aren't relevant
+				 * until the schemata is written, and the mode
+				 * becomes RDT_MODE_PSEUDO_LOCKED.
+				 */
+				continue;
 			/*
 			 * If CDP is active include peer domain's
 			 * usage to ensure there is no overlap
-- 
2.20.1