Merge tag 'x86-urgent-2020-06-11' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull more x86 updates from Thomas Gleixner:
 "A set of fixes and updates for x86:

   - Unbreak paravirt VDSO clocks.

     While the VDSO code was moved into lib for sharing a subtle check
     for the validity of paravirt clocks got replaced. While the
     replacement works perfectly fine for bare metal as the update of
     the VDSO clock mode is synchronous, it fails for paravirt clocks
     because the hypervisor can invalidate them asynchronously.

     Bring it back as an optional function so it does not inflict this
     on architectures which are free of PV damage.

   - Fix the jiffies to jiffies64 mapping on 64bit so it does not
     trigger an ODR violation on newer compilers

   - Three fixes for the SSBD and *IB* speculation mitigation maze to
     ensure consistency, not disabling of some *IB* variants wrongly and
     to prevent a rogue cross process shutdown of SSBD. All marked for
     stable.

   - Add yet more CPU models to the splitlock detection capable list
     !@#%$!

   - Bring the pr_info() back which tells that TSC deadline timer is
     enabled.

   - Reboot quirk for MacBook6,1"

* tag 'x86-urgent-2020-06-11' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/vdso: Unbreak paravirt VDSO clocks
  lib/vdso: Provide sanity check for cycles (again)
  clocksource: Remove obsolete ifdef
  x86_64: Fix jiffies ODR violation
  x86/speculation: PR_SPEC_FORCE_DISABLE enforcement for indirect branches.
  x86/speculation: Prevent rogue cross-process SSBD shutdown
  x86/speculation: Avoid force-disabling IBPB based on STIBP and enhanced IBRS.
  x86/cpu: Add Sapphire Rapids CPU model number
  x86/split_lock: Add Icelake microserver and Tigerlake CPU models
  x86/apic: Make TSC deadline timer detection message visible
  x86/reboot/quirks: Add MacBook6,1 reboot quirk

1 files changed, 10 insertions, 18 deletions

diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 8e3d0347b664..f362ce0d5ac0 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -545,28 +545,20 @@ static __always_inline void __speculation_ctrl_update(unsigned long tifp,
 
 	lockdep_assert_irqs_disabled();
 
-	/*
-	 * If TIF_SSBD is different, select the proper mitigation
-	 * method. Note that if SSBD mitigation is disabled or permanentely
-	 * enabled this branch can't be taken because nothing can set
-	 * TIF_SSBD.
-	 */
-	if (tif_diff & _TIF_SSBD) {
-		if (static_cpu_has(X86_FEATURE_VIRT_SSBD)) {
+	/* Handle change of TIF_SSBD depending on the mitigation method. */
+	if (static_cpu_has(X86_FEATURE_VIRT_SSBD)) {
+		if (tif_diff & _TIF_SSBD)
 			amd_set_ssb_virt_state(tifn);
-		} else if (static_cpu_has(X86_FEATURE_LS_CFG_SSBD)) {
+	} else if (static_cpu_has(X86_FEATURE_LS_CFG_SSBD)) {
+		if (tif_diff & _TIF_SSBD)
 			amd_set_core_ssb_state(tifn);
-		} else if (static_cpu_has(X86_FEATURE_SPEC_CTRL_SSBD) ||
-			   static_cpu_has(X86_FEATURE_AMD_SSBD)) {
-			msr |= ssbd_tif_to_spec_ctrl(tifn);
-			updmsr  = true;
-		}
+	} else if (static_cpu_has(X86_FEATURE_SPEC_CTRL_SSBD) ||
+		   static_cpu_has(X86_FEATURE_AMD_SSBD)) {
+		updmsr |= !!(tif_diff & _TIF_SSBD);
+		msr |= ssbd_tif_to_spec_ctrl(tifn);
 	}
 
-	/*
-	 * Only evaluate TIF_SPEC_IB if conditional STIBP is enabled,
-	 * otherwise avoid the MSR write.
-	 */
+	/* Only evaluate TIF_SPEC_IB if conditional STIBP is enabled. */
 	if (IS_ENABLED(CONFIG_SMP) &&
 	    static_branch_unlikely(&switch_to_cond_stibp)) {
 		updmsr |= !!(tif_diff & _TIF_SPEC_IB);