From: James Morse Date: Tue, 11 Mar 2025 18:36:46 +0000 (+0000) Subject: x86/resctrl: Fix allocation of cleanest CLOSID on platforms with no monitors X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=a121798ae669351ec0697c94f71c3a692b2a755b;p=users%2Fwilly%2Flinux.git x86/resctrl: Fix allocation of cleanest CLOSID on platforms with no monitors Commit 6eac36bb9eb0 ("x86/resctrl: Allocate the cleanest CLOSID by searching closid_num_dirty_rmid") added logic that causes resctrl to search for the CLOSID with the fewest dirty cache lines when creating a new control group, if requested by the arch code. This depends on the values read from the llc_occupancy counters. The logic is applicable to architectures where the CLOSID effectively forms part of the monitoring identifier and so do not allow complete freedom to choose an unused monitoring identifier for a given CLOSID. 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. Fixes: 6eac36bb9eb0 ("x86/resctrl: Allocate the cleanest CLOSID by searching closid_num_dirty_rmid") Signed-off-by: James Morse Signed-off-by: Borislav Petkov (AMD) Reviewed-by: Shaopeng Tan Reviewed-by: David Hildenbrand Reviewed-by: Reinette Chatre Reviewed-by: Tony Luck Reviewed-by: Fenghua Yu Reviewed-by: Babu Moger Tested-by: Carl Worth # arm64 Tested-by: Shaopeng Tan Tested-by: Peter Newman Tested-by: Amit Singh Tomar # arm64 Tested-by: Shanker Donthineni # arm64 Tested-by: Babu Moger Link: https://lore.kernel.org/r/20250311183715.16445-2-james.morse@arm.com --- diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c index 6419e04d8a7b..04b653d613e8 100644 --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c @@ -157,7 +157,8 @@ 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;