Commit-ID: 80b71c340f17705ec145911b9a193ea781811b16 Gitweb: https://git.kernel.org/tip/80b71c340f17705ec145911b9a193ea781811b16 Author: Reinette Chatre <reinette.chatre@xxxxxxxxx> AuthorDate: Mon, 10 Dec 2018 13:21:54 -0800 Committer: Borislav Petkov <bp@xxxxxxx> CommitDate: Tue, 11 Dec 2018 21:59:01 +0100 x86/intel_rdt: Ensure a CPU remains online for the region's pseudo-locking sequence The user triggers the creation of a pseudo-locked region when writing the requested schemata to the schemata resctrl file. The pseudo-locking of a region is required to be done on a CPU that is associated with the cache on which the pseudo-locked region will reside. In order to run the locking code on a specific CPU, the needed CPU has to be selected and ensured to remain online during the entire locking sequence. At this time, the cpu_hotplug_lock is not taken during the pseudo-lock region creation and it is thus possible for a CPU to be selected to run the pseudo-locking code and then that CPU to go offline before the thread is able to run on it. Fix this by ensuring that the cpu_hotplug_lock is taken while the CPU on which code has to run needs to be controlled. Since the cpu_hotplug_lock is always taken before rdtgroup_mutex the lock order is maintained. Fixes: e0bdfe8e36f3 ("x86/intel_rdt: Support creation/removal of pseudo-locked region") Signed-off-by: Reinette Chatre <reinette.chatre@xxxxxxxxx> Signed-off-by: Borislav Petkov <bp@xxxxxxx> Cc: "H. Peter Anvin" <hpa@xxxxxxxxx> Cc: Fenghua Yu <fenghua.yu@xxxxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: Tony Luck <tony.luck@xxxxxxxxx> Cc: gavin.hindman@xxxxxxxxx Cc: jithu.joseph@xxxxxxxxx Cc: stable <stable@xxxxxxxxxxxxxxx> Cc: x86-ml <x86@xxxxxxxxxx> Link: https://lkml.kernel.org/r/b7b17432a80f95a1fa21a1698ba643014f58ad31.1544476425.git.reinette.chatre@xxxxxxxxx --- arch/x86/kernel/cpu/intel_rdt_ctrlmondata.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/arch/x86/kernel/cpu/intel_rdt_ctrlmondata.c b/arch/x86/kernel/cpu/intel_rdt_ctrlmondata.c index 27937458c231..efa4a519f5e5 100644 --- a/arch/x86/kernel/cpu/intel_rdt_ctrlmondata.c +++ b/arch/x86/kernel/cpu/intel_rdt_ctrlmondata.c @@ -23,6 +23,7 @@ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt +#include <linux/cpu.h> #include <linux/kernfs.h> #include <linux/seq_file.h> #include <linux/slab.h> @@ -310,9 +311,11 @@ ssize_t rdtgroup_schemata_write(struct kernfs_open_file *of, return -EINVAL; buf[nbytes - 1] = '\0'; + cpus_read_lock(); rdtgrp = rdtgroup_kn_lock_live(of->kn); if (!rdtgrp) { rdtgroup_kn_unlock(of->kn); + cpus_read_unlock(); return -ENOENT; } rdt_last_cmd_clear(); @@ -367,6 +370,7 @@ ssize_t rdtgroup_schemata_write(struct kernfs_open_file *of, out: rdtgroup_kn_unlock(of->kn); + cpus_read_unlock(); return ret ?: nbytes; }
