Merge tag 'x86_cpu_for_7.1-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 cpu updates from Dave Hansen:

 - Complete LASS enabling: deal with vsyscall and EFI

   The existing Linear Address Space Separation (LASS) support punted
   on support for common EFI and vsyscall configs. Complete the
   implementation by supporting EFI and vsyscall=xonly.

 - Clean up CPUID usage in newer Intel "avs" audio driver and update the
   x86-cpuid-db file

* tag 'x86_cpu_for_7.1-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  tools/x86/kcpuid: Update bitfields to x86-cpuid-db v3.0
  ASoC: Intel: avs: Include CPUID header at file scope
  ASoC: Intel: avs: Check maximum valid CPUID leaf
  x86/cpu: Remove LASS restriction on vsyscall emulation
  x86/vsyscall: Disable LASS if vsyscall mode is set to EMULATE
  x86/vsyscall: Restore vsyscall=xonly mode under LASS
  x86/traps: Consolidate user fixups in the #GP handler
  x86/vsyscall: Reorganize the page fault emulation code
  x86/cpu: Remove LASS restriction on EFI
  x86/efi: Disable LASS while executing runtime services
  x86/cpu: Defer LASS enabling until userspace comes up

1 files changed, 18 insertions, 17 deletions

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index ec0670114efa..8060cccd24d8 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -409,27 +409,29 @@ out:
 	cr4_clear_bits(X86_CR4_UMIP);
 }
 
-static __always_inline void setup_lass(struct cpuinfo_x86 *c)
+static int enable_lass(unsigned int cpu)
+{
+	cr4_set_bits(X86_CR4_LASS);
+
+	return 0;
+}
+
+/*
+ * Finalize features that need to be enabled just before entering
+ * userspace. Note that this only runs on a single CPU. Use appropriate
+ * callbacks if all the CPUs need to reflect the same change.
+ */
+static int cpu_finalize_pre_userspace(void)
 {
 	if (!cpu_feature_enabled(X86_FEATURE_LASS))
-		return;
+		return 0;
 
-	/*
-	 * Legacy vsyscall page access causes a #GP when LASS is active.
-	 * Disable LASS because the #GP handler doesn't support vsyscall
-	 * emulation.
-	 *
-	 * Also disable LASS when running under EFI, as some runtime and
-	 * boot services rely on 1:1 mappings in the lower half.
-	 */
-	if (IS_ENABLED(CONFIG_X86_VSYSCALL_EMULATION) ||
-	    IS_ENABLED(CONFIG_EFI)) {
-		setup_clear_cpu_cap(X86_FEATURE_LASS);
-		return;
-	}
+	/* Runs on all online CPUs and future CPUs that come online. */
+	cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "x86/lass:enable", enable_lass, NULL);
 
-	cr4_set_bits(X86_CR4_LASS);
+	return 0;
 }
+late_initcall(cpu_finalize_pre_userspace);
 
 /* These bits should not change their value after CPU init is finished. */
 static const unsigned long cr4_pinned_mask = X86_CR4_SMEP | X86_CR4_SMAP | X86_CR4_UMIP |
@@ -2061,7 +2063,6 @@ static void identify_cpu(struct cpuinfo_x86 *c)
 	setup_smep(c);
 	setup_smap(c);
 	setup_umip(c);
-	setup_lass(c);
 
 	/*
 	 * The vendor-specific functions might have changed features.