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From: James Morse <james.morse@arm.com>
To: x86@kernel.org,
	linux-kernel@vger.kernel.org
Cc: Fenghua Yu <fenghua.yu@intel.com>,
	Reinette Chatre <reinette.chatre@intel.com>,
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	David Hildenbrand <david@redhat.com>,
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	Dave Martin <dave.martin@arm.com>
Subject: [PATCH v1 01/31] x86/resctrl: Fix allocation of cleanest CLOSID on platforms with no monitors
Date: Thu, 21 Mar 2024 16:50:36 +0000
Message-Id: <20240321165106.31602-2-james.morse@arm.com>
In-Reply-To: <20240321165106.31602-1-james.morse@arm.com>
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commit 6eac36bb9eb0 ("x86/resctrl: Allocate the cleanest CLOSID by
searching closid_num_dirty_rmid") added a Kconfig option that causes
resctrl to search for the CLOSID with the fewest dirty cache lines when
creating a new control group. This depends on the values read from the
llc_occupancy counters.

This support missed that some platforms may not have these counters.
This causes a NULL pointer dereference when creating a new control
group as the array was not allocated by dom_data_init().

As this feature isn't necessary on platforms that don't have cache
occupancy monitors, add this to the check that occurs when a new
control group is allocated.

The existing code is not selected by any upstream platform, it makes
no sense to backport this patch to stable.

Signed-off-by: James Morse <james.morse@arm.com>
---
 arch/x86/kernel/cpu/resctrl/rdtgroup.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index 011e17efb1a6..1767c1affa60 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -149,7 +149,8 @@ static int closid_alloc(void)
 
 	lockdep_assert_held(&rdtgroup_mutex);
 
-	if (IS_ENABLED(CONFIG_RESCTRL_RMID_DEPENDS_ON_CLOSID)) {
+	if (IS_ENABLED(CONFIG_RESCTRL_RMID_DEPENDS_ON_CLOSID) &&
+	    is_llc_occupancy_enabled()) {
 		cleanest_closid = resctrl_find_cleanest_closid();
 		if (cleanest_closid < 0)
 			return cleanest_closid;
-- 
2.39.2