aboutsummaryrefslogtreecommitdiff
path: root/arch/x86/kernel
diff options
context:
space:
mode:
authorLinus Torvalds <torvalds@linux-foundation.org>2022-05-23 19:24:47 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2022-05-23 19:24:47 -0700
commit3e2cbc016b1d08463925db9b9bd3bd253f64b8b0 (patch)
treef1bac77db344cc74382151e8c2a7a74085b98219 /arch/x86/kernel
parent916654201008d5fb4d5f5dcf0b373d291da615ac (diff)
parent0180a1e823d7c41d9a1c19f38e6069b38fe60c87 (diff)
Merge tag 'x86_splitlock_for_v5.19_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 splitlock updates from Borislav Petkov: - Add Raptor Lake to the set of CPU models which support splitlock - Make life miserable for apps using split locks by slowing them down considerably while the rest of the system remains responsive. The hope is it will hurt more and people will really fix their misaligned locks apps. As a result, free a TIF bit. * tag 'x86_splitlock_for_v5.19_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: x86/split_lock: Enable the split lock feature on Raptor Lake x86/split-lock: Remove unused TIF_SLD bit x86/split_lock: Make life miserable for split lockers
Diffstat (limited to 'arch/x86/kernel')
-rw-r--r--arch/x86/kernel/cpu/intel.c76
-rw-r--r--arch/x86/kernel/process.c3
2 files changed, 54 insertions, 25 deletions
diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
index f7a5370a9b3b..e6c37f38c5ea 100644
--- a/arch/x86/kernel/cpu/intel.c
+++ b/arch/x86/kernel/cpu/intel.c
@@ -7,10 +7,13 @@
#include <linux/smp.h>
#include <linux/sched.h>
#include <linux/sched/clock.h>
+#include <linux/semaphore.h>
#include <linux/thread_info.h>
#include <linux/init.h>
#include <linux/uaccess.h>
+#include <linux/workqueue.h>
#include <linux/delay.h>
+#include <linux/cpuhotplug.h>
#include <asm/cpufeature.h>
#include <asm/msr.h>
@@ -999,6 +1002,8 @@ static const struct {
static struct ratelimit_state bld_ratelimit;
+static DEFINE_SEMAPHORE(buslock_sem);
+
static inline bool match_option(const char *arg, int arglen, const char *opt)
{
int len = strlen(opt), ratelimit;
@@ -1109,18 +1114,52 @@ static void split_lock_init(void)
split_lock_verify_msr(sld_state != sld_off);
}
+static void __split_lock_reenable(struct work_struct *work)
+{
+ sld_update_msr(true);
+ up(&buslock_sem);
+}
+
+/*
+ * If a CPU goes offline with pending delayed work to re-enable split lock
+ * detection then the delayed work will be executed on some other CPU. That
+ * handles releasing the buslock_sem, but because it executes on a
+ * different CPU probably won't re-enable split lock detection. This is a
+ * problem on HT systems since the sibling CPU on the same core may then be
+ * left running with split lock detection disabled.
+ *
+ * Unconditionally re-enable detection here.
+ */
+static int splitlock_cpu_offline(unsigned int cpu)
+{
+ sld_update_msr(true);
+
+ return 0;
+}
+
+static DECLARE_DELAYED_WORK(split_lock_reenable, __split_lock_reenable);
+
static void split_lock_warn(unsigned long ip)
{
- pr_warn_ratelimited("#AC: %s/%d took a split_lock trap at address: 0x%lx\n",
- current->comm, current->pid, ip);
+ int cpu;
- /*
- * Disable the split lock detection for this task so it can make
- * progress and set TIF_SLD so the detection is re-enabled via
- * switch_to_sld() when the task is scheduled out.
- */
+ if (!current->reported_split_lock)
+ pr_warn_ratelimited("#AC: %s/%d took a split_lock trap at address: 0x%lx\n",
+ current->comm, current->pid, ip);
+ current->reported_split_lock = 1;
+
+ /* misery factor #1, sleep 10ms before trying to execute split lock */
+ if (msleep_interruptible(10) > 0)
+ return;
+ /* Misery factor #2, only allow one buslocked disabled core at a time */
+ if (down_interruptible(&buslock_sem) == -EINTR)
+ return;
+ cpu = get_cpu();
+ schedule_delayed_work_on(cpu, &split_lock_reenable, 2);
+
+ /* Disable split lock detection on this CPU to make progress */
sld_update_msr(false);
- set_tsk_thread_flag(current, TIF_SLD);
+ put_cpu();
}
bool handle_guest_split_lock(unsigned long ip)
@@ -1194,18 +1233,6 @@ void handle_bus_lock(struct pt_regs *regs)
}
/*
- * This function is called only when switching between tasks with
- * different split-lock detection modes. It sets the MSR for the
- * mode of the new task. This is right most of the time, but since
- * the MSR is shared by hyperthreads on a physical core there can
- * be glitches when the two threads need different modes.
- */
-void switch_to_sld(unsigned long tifn)
-{
- sld_update_msr(!(tifn & _TIF_SLD));
-}
-
-/*
* Bits in the IA32_CORE_CAPABILITIES are not architectural, so they should
* only be trusted if it is confirmed that a CPU model implements a
* specific feature at a particular bit position.
@@ -1230,6 +1257,7 @@ static const struct x86_cpu_id split_lock_cpu_ids[] __initconst = {
X86_MATCH_INTEL_FAM6_MODEL(SAPPHIRERAPIDS_X, 1),
X86_MATCH_INTEL_FAM6_MODEL(ALDERLAKE, 1),
X86_MATCH_INTEL_FAM6_MODEL(ALDERLAKE_L, 1),
+ X86_MATCH_INTEL_FAM6_MODEL(RAPTORLAKE, 1),
{}
};
@@ -1274,10 +1302,14 @@ static void sld_state_show(void)
pr_info("disabled\n");
break;
case sld_warn:
- if (boot_cpu_has(X86_FEATURE_SPLIT_LOCK_DETECT))
+ if (boot_cpu_has(X86_FEATURE_SPLIT_LOCK_DETECT)) {
pr_info("#AC: crashing the kernel on kernel split_locks and warning on user-space split_locks\n");
- else if (boot_cpu_has(X86_FEATURE_BUS_LOCK_DETECT))
+ if (cpuhp_setup_state(CPUHP_AP_ONLINE_DYN,
+ "x86/splitlock", NULL, splitlock_cpu_offline) < 0)
+ pr_warn("No splitlock CPU offline handler\n");
+ } else if (boot_cpu_has(X86_FEATURE_BUS_LOCK_DETECT)) {
pr_info("#DB: warning on user-space bus_locks\n");
+ }
break;
case sld_fatal:
if (boot_cpu_has(X86_FEATURE_SPLIT_LOCK_DETECT)) {
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index cbe6aa3f649d..58fb48d3004f 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -684,9 +684,6 @@ void __switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p)
/* Enforce MSR update to ensure consistent state */
__speculation_ctrl_update(~tifn, tifn);
}
-
- if ((tifp ^ tifn) & _TIF_SLD)
- switch_to_sld(tifn);
}
/*