Introduce split_lock_virt_switch(), which is used for toggling split
lock detection setting as well as updating TIF_SLD_DISABLED flag to make
them consistent. Note, it can only be used in sld warn mode, i.e.,
X86_FEATURE_SPLIT_LOCK_DETECT && !X86_FEATURE_SLD_FATAL.
The FATAL check is handled by wrappers, split_lock_set_guest() and
split_lock_restore_host(), that will be used by KVM when virtualizing
split lock detection for guest in the future.
Signed-off-by: Xiaoyao Li <xiaoyao.li@xxxxxxxxx>
---
arch/x86/include/asm/cpu.h | 34 ++++++++++++++++++++++++++++++++++
arch/x86/kernel/cpu/intel.c | 20 ++++++++++++++++++++
2 files changed, 54 insertions(+)
diff --git a/arch/x86/include/asm/cpu.h b/arch/x86/include/asm/cpu.h
index da78ccbd493b..2971a29d5094 100644
--- a/arch/x86/include/asm/cpu.h
+++ b/arch/x86/include/asm/cpu.h
@@ -45,6 +45,7 @@ extern void __init cpu_set_core_cap_bits(struct cpuinfo_x86 *c);
extern void switch_to_sld(unsigned long tifn);
extern bool handle_user_split_lock(struct pt_regs *regs, long error_code);
extern bool handle_guest_split_lock(unsigned long ip);
+extern bool split_lock_virt_switch(bool on);
#else
static inline void __init cpu_set_core_cap_bits(struct cpuinfo_x86 *c) {}
static inline void switch_to_sld(unsigned long tifn) {}
@@ -57,7 +58,40 @@ static inline bool handle_guest_split_lock(unsigned long ip)
{
return false;
}
+
+static inline bool split_lock_virt_switch(bool on) { return false; }
#endif
+
+/**
+ * split_lock_set_guest - Set SLD state for a guest
+ * @guest_sld_on: If SLD is on in the guest
+ *
+ * returns: %true if SLD was enabled in the task
+ *
+ * Must be called when X86_FEATURE_SPLIT_LOCK_DETECT is available.
+ */
+static inline bool split_lock_set_guest(bool guest_sld_on)
+{
+ if (static_cpu_has(X86_FEATURE_SLD_FATAL))
+ return true;
+
+ return split_lock_virt_switch(guest_sld_on);
+}
+
+/**
+ * split_lock_restore_host - Restore host SLD state
+ * @host_sld_on: If SLD is on in the host
+ *
+ * Must be called when X86_FEATURE_SPLIT_LOCK_DETECT is available.
+ */
+static inline void split_lock_restore_host(bool host_sld_on)
+{
+ if (static_cpu_has(X86_FEATURE_SLD_FATAL))
+ return;
+
+ split_lock_virt_switch(host_sld_on);
+}
+
#ifdef CONFIG_IA32_FEAT_CTL
void init_ia32_feat_ctl(struct cpuinfo_x86 *c);
#else
diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
index 06de03974e66..5f44e0de04b9 100644
--- a/arch/x86/kernel/cpu/intel.c
+++ b/arch/x86/kernel/cpu/intel.c
@@ -1078,6 +1078,26 @@ static void split_lock_init(void)
split_lock_verify_msr(boot_cpu_has(X86_FEATURE_SPLIT_LOCK_DETECT));
}
+/*
+ * It should never be called directly but should use split_lock_set_guest()
+ * and split_lock_restore_host() instead.
+ *
+ * The caller needs to be in preemption disabled context to ensure
+ * MSR state and TIF_SLD_DISABLED state consistent.
+ */
+bool split_lock_virt_switch(bool on)
+{
+ bool was_on = !test_thread_flag(TIF_SLD_DISABLED);
+
+ if (on != was_on) {
+ sld_update_msr(on);
+ update_thread_flag(TIF_SLD_DISABLED, !on);
+ }
+
+ return was_on;
+}
+EXPORT_SYMBOL_GPL(split_lock_virt_switch);
+
static void split_lock_warn(unsigned long ip)
{
pr_warn_ratelimited("#AC: %s/%d took a split_lock trap at address: 0x%lx\n",
--
2.18.4
