3 files changed, 16 insertions, 9 deletions

diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index 07f5030073bb..f14cdf951249 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -310,7 +310,7 @@ static inline void indirect_branch_prediction_barrier(void)
 /* The Intel SPEC CTRL MSR base value cache */
 extern u64 x86_spec_ctrl_base;
 DECLARE_PER_CPU(u64, x86_spec_ctrl_current);
-extern void write_spec_ctrl_current(u64 val, bool force);
+extern void update_spec_ctrl_cond(u64 val);
 extern u64 spec_ctrl_current(void);
 
 /*
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index a300a19255b6..e2e22a5740a4 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -59,11 +59,18 @@ EXPORT_SYMBOL_GPL(x86_spec_ctrl_current);
 
 static DEFINE_MUTEX(spec_ctrl_mutex);
 
+/* Update SPEC_CTRL MSR and its cached copy unconditionally */
+static void update_spec_ctrl(u64 val)
+{
+	this_cpu_write(x86_spec_ctrl_current, val);
+	wrmsrl(MSR_IA32_SPEC_CTRL, val);
+}
+
 /*
  * Keep track of the SPEC_CTRL MSR value for the current task, which may differ
  * from x86_spec_ctrl_base due to STIBP/SSB in __speculation_ctrl_update().
  */
-void write_spec_ctrl_current(u64 val, bool force)
+void update_spec_ctrl_cond(u64 val)
 {
 	if (this_cpu_read(x86_spec_ctrl_current) == val)
 		return;
@@ -74,7 +81,7 @@ void write_spec_ctrl_current(u64 val, bool force)
 	 * When KERNEL_IBRS this MSR is written on return-to-user, unless
 	 * forced the update can be delayed until that time.
 	 */
-	if (force || !cpu_feature_enabled(X86_FEATURE_KERNEL_IBRS))
+	if (!cpu_feature_enabled(X86_FEATURE_KERNEL_IBRS))
 		wrmsrl(MSR_IA32_SPEC_CTRL, val);
 }
 
@@ -1291,7 +1298,7 @@ static void __init spec_ctrl_disable_kernel_rrsba(void)
 
 	if (ia32_cap & ARCH_CAP_RRSBA) {
 		x86_spec_ctrl_base |= SPEC_CTRL_RRSBA_DIS_S;
-		write_spec_ctrl_current(x86_spec_ctrl_base, true);
+		update_spec_ctrl(x86_spec_ctrl_base);
 	}
 }
 
@@ -1413,7 +1420,7 @@ static void __init spectre_v2_select_mitigation(void)
 
 	if (spectre_v2_in_ibrs_mode(mode)) {
 		x86_spec_ctrl_base |= SPEC_CTRL_IBRS;
-		write_spec_ctrl_current(x86_spec_ctrl_base, true);
+		update_spec_ctrl(x86_spec_ctrl_base);
 	}
 
 	switch (mode) {
@@ -1527,7 +1534,7 @@ static void __init spectre_v2_select_mitigation(void)
 static void update_stibp_msr(void * __unused)
 {
 	u64 val = spec_ctrl_current() | (x86_spec_ctrl_base & SPEC_CTRL_STIBP);
-	write_spec_ctrl_current(val, true);
+	update_spec_ctrl(val);
 }
 
 /* Update x86_spec_ctrl_base in case SMT state changed. */
@@ -1760,7 +1767,7 @@ static enum ssb_mitigation __init __ssb_select_mitigation(void)
 			x86_amd_ssb_disable();
 		} else {
 			x86_spec_ctrl_base |= SPEC_CTRL_SSBD;
-			write_spec_ctrl_current(x86_spec_ctrl_base, true);
+			update_spec_ctrl(x86_spec_ctrl_base);
 		}
 	}
 
@@ -1978,7 +1985,7 @@ int arch_prctl_spec_ctrl_get(struct task_struct *task, unsigned long which)
 void x86_spec_ctrl_setup_ap(void)
 {
 	if (boot_cpu_has(X86_FEATURE_MSR_SPEC_CTRL))
-		write_spec_ctrl_current(x86_spec_ctrl_base, true);
+		update_spec_ctrl(x86_spec_ctrl_base);
 
 	if (ssb_mode == SPEC_STORE_BYPASS_DISABLE)
 		x86_amd_ssb_disable();
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 4505d845daba..383afcc1098b 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -556,7 +556,7 @@ static __always_inline void __speculation_ctrl_update(unsigned long tifp,
 	}
 
 	if (updmsr)
-		write_spec_ctrl_current(msr, false);
+		update_spec_ctrl_cond(msr);
 }
 
 static unsigned long speculation_ctrl_update_tif(struct task_struct *tsk)