Merge branch 'x86-pti-for-linus' of git://git.kernel.org/pub/scm/linu…

…x/kernel/git/tip/tip

Pull x86 pti updates from Thomas Gleixner:
 "No point in speculating what's in this parcel:

   - Drop the swap storage limit when L1TF is disabled so the full space
     is available

   - Add support for the new AMD STIBP always on mitigation mode

   - Fix a bunch of STIPB typos"

* 'x86-pti-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/speculation: Add support for STIBP always-on preferred mode
  x86/speculation/l1tf: Drop the swap storage limit restriction when l1tf=off
  x86/speculation: Change misspelled STIPB to STIBP

Documentation/admin-guide/kernel-parameters.txt

@@ -2099,6 +2099,9 @@
 			off
 				Disables hypervisor mitigations and doesn't
 				emit any warnings.
+				It also drops the swap size and available
+				RAM limit restriction on both hypervisor and
+				bare metal.
 
 			Default is 'flush'.
 

Documentation/admin-guide/l1tf.rst

@@ -405,6 +405,9 @@ time with the option "l1tf=". The valid arguments for this option are:
 
   off		Disables hypervisor mitigations and doesn't emit any
 		warnings.
+		It also drops the swap size and available RAM limit restrictions
+		on both hypervisor and bare metal.
+
   ============  =============================================================
 
 The default is 'flush'. For details about L1D flushing see :ref:`l1d_flush`.
@@ -576,7 +579,8 @@ Default mitigations
   The kernel default mitigations for vulnerable processors are:
 
   - PTE inversion to protect against malicious user space. This is done
-    unconditionally and cannot be controlled.
+    unconditionally and cannot be controlled. The swap storage is limited
+    to ~16TB.
 
   - L1D conditional flushing on VMENTER when EPT is enabled for
     a guest.

arch/x86/include/asm/cpufeatures.h

@@ -284,6 +284,7 @@
 #define X86_FEATURE_AMD_IBPB		(13*32+12) /* "" Indirect Branch Prediction Barrier */
 #define X86_FEATURE_AMD_IBRS		(13*32+14) /* "" Indirect Branch Restricted Speculation */
 #define X86_FEATURE_AMD_STIBP		(13*32+15) /* "" Single Thread Indirect Branch Predictors */
+#define X86_FEATURE_AMD_STIBP_ALWAYS_ON	(13*32+17) /* "" Single Thread Indirect Branch Predictors always-on preferred */
 #define X86_FEATURE_AMD_SSBD		(13*32+24) /* "" Speculative Store Bypass Disable */
 #define X86_FEATURE_VIRT_SSBD		(13*32+25) /* Virtualized Speculative Store Bypass Disable */
 #define X86_FEATURE_AMD_SSB_NO		(13*32+26) /* "" Speculative Store Bypass is fixed in hardware. */

arch/x86/include/asm/nospec-branch.h

@@ -232,6 +232,7 @@ enum spectre_v2_mitigation {
 enum spectre_v2_user_mitigation {
 	SPECTRE_V2_USER_NONE,
 	SPECTRE_V2_USER_STRICT,
+	SPECTRE_V2_USER_STRICT_PREFERRED,
 	SPECTRE_V2_USER_PRCTL,
 	SPECTRE_V2_USER_SECCOMP,
 };

arch/x86/kernel/cpu/bugs.c

@@ -54,7 +54,7 @@ static u64 __ro_after_init x86_spec_ctrl_mask = SPEC_CTRL_IBRS;
 u64 __ro_after_init x86_amd_ls_cfg_base;
 u64 __ro_after_init x86_amd_ls_cfg_ssbd_mask;
 
-/* Control conditional STIPB in switch_to() */
+/* Control conditional STIBP in switch_to() */
 DEFINE_STATIC_KEY_FALSE(switch_to_cond_stibp);
 /* Control conditional IBPB in switch_mm() */
 DEFINE_STATIC_KEY_FALSE(switch_mm_cond_ibpb);
@@ -262,10 +262,11 @@ enum spectre_v2_user_cmd {
 };
 
 static const char * const spectre_v2_user_strings[] = {
-	[SPECTRE_V2_USER_NONE]		= "User space: Vulnerable",
-	[SPECTRE_V2_USER_STRICT]	= "User space: Mitigation: STIBP protection",
-	[SPECTRE_V2_USER_PRCTL]		= "User space: Mitigation: STIBP via prctl",
-	[SPECTRE_V2_USER_SECCOMP]	= "User space: Mitigation: STIBP via seccomp and prctl",
+	[SPECTRE_V2_USER_NONE]			= "User space: Vulnerable",
+	[SPECTRE_V2_USER_STRICT]		= "User space: Mitigation: STIBP protection",
+	[SPECTRE_V2_USER_STRICT_PREFERRED]	= "User space: Mitigation: STIBP always-on protection",
+	[SPECTRE_V2_USER_PRCTL]			= "User space: Mitigation: STIBP via prctl",
+	[SPECTRE_V2_USER_SECCOMP]		= "User space: Mitigation: STIBP via seccomp and prctl",
 };
 
 static const struct {
@@ -355,6 +356,15 @@ spectre_v2_user_select_mitigation(enum spectre_v2_mitigation_cmd v2_cmd)
 		break;
 	}
 
+	/*
+	 * At this point, an STIBP mode other than "off" has been set.
+	 * If STIBP support is not being forced, check if STIBP always-on
+	 * is preferred.
+	 */
+	if (mode != SPECTRE_V2_USER_STRICT &&
+	    boot_cpu_has(X86_FEATURE_AMD_STIBP_ALWAYS_ON))
+		mode = SPECTRE_V2_USER_STRICT_PREFERRED;
+
 	/* Initialize Indirect Branch Prediction Barrier */
 	if (boot_cpu_has(X86_FEATURE_IBPB)) {
 		setup_force_cpu_cap(X86_FEATURE_USE_IBPB);
@@ -379,12 +389,12 @@ spectre_v2_user_select_mitigation(enum spectre_v2_mitigation_cmd v2_cmd)
 			"always-on" : "conditional");
 	}
 
-	/* If enhanced IBRS is enabled no STIPB required */
+	/* If enhanced IBRS is enabled no STIBP required */
 	if (spectre_v2_enabled == SPECTRE_V2_IBRS_ENHANCED)
 		return;
 
 	/*
-	 * If SMT is not possible or STIBP is not available clear the STIPB
+	 * If SMT is not possible or STIBP is not available clear the STIBP
 	 * mode.
 	 */
 	if (!smt_possible || !boot_cpu_has(X86_FEATURE_STIBP))
@@ -610,6 +620,7 @@ void arch_smt_update(void)
 	case SPECTRE_V2_USER_NONE:
 		break;
 	case SPECTRE_V2_USER_STRICT:
+	case SPECTRE_V2_USER_STRICT_PREFERRED:
 		update_stibp_strict();
 		break;
 	case SPECTRE_V2_USER_PRCTL:
@@ -812,7 +823,8 @@ static int ib_prctl_set(struct task_struct *task, unsigned long ctrl)
 		 * Indirect branch speculation is always disabled in strict
 		 * mode.
 		 */
-		if (spectre_v2_user == SPECTRE_V2_USER_STRICT)
+		if (spectre_v2_user == SPECTRE_V2_USER_STRICT ||
+		    spectre_v2_user == SPECTRE_V2_USER_STRICT_PREFERRED)
 			return -EPERM;
 		task_clear_spec_ib_disable(task);
 		task_update_spec_tif(task);
@@ -825,7 +837,8 @@ static int ib_prctl_set(struct task_struct *task, unsigned long ctrl)
 		 */
 		if (spectre_v2_user == SPECTRE_V2_USER_NONE)
 			return -EPERM;
-		if (spectre_v2_user == SPECTRE_V2_USER_STRICT)
+		if (spectre_v2_user == SPECTRE_V2_USER_STRICT ||
+		    spectre_v2_user == SPECTRE_V2_USER_STRICT_PREFERRED)
 			return 0;
 		task_set_spec_ib_disable(task);
 		if (ctrl == PR_SPEC_FORCE_DISABLE)
@@ -896,6 +909,7 @@ static int ib_prctl_get(struct task_struct *task)
 			return PR_SPEC_PRCTL | PR_SPEC_DISABLE;
 		return PR_SPEC_PRCTL | PR_SPEC_ENABLE;
 	case SPECTRE_V2_USER_STRICT:
+	case SPECTRE_V2_USER_STRICT_PREFERRED:
 		return PR_SPEC_DISABLE;
 	default:
 		return PR_SPEC_NOT_AFFECTED;
@@ -1002,7 +1016,8 @@ static void __init l1tf_select_mitigation(void)
 #endif
 
 	half_pa = (u64)l1tf_pfn_limit() << PAGE_SHIFT;
-	if (e820__mapped_any(half_pa, ULLONG_MAX - half_pa, E820_TYPE_RAM)) {
+	if (l1tf_mitigation != L1TF_MITIGATION_OFF &&
+			e820__mapped_any(half_pa, ULLONG_MAX - half_pa, E820_TYPE_RAM)) {
 		pr_warn("System has more than MAX_PA/2 memory. L1TF mitigation not effective.\n");
 		pr_info("You may make it effective by booting the kernel with mem=%llu parameter.\n",
 				half_pa);
@@ -1088,6 +1103,8 @@ static char *stibp_state(void)
 		return ", STIBP: disabled";
 	case SPECTRE_V2_USER_STRICT:
 		return ", STIBP: forced";
+	case SPECTRE_V2_USER_STRICT_PREFERRED:
+		return ", STIBP: always-on";
 	case SPECTRE_V2_USER_PRCTL:
 	case SPECTRE_V2_USER_SECCOMP:
 		if (static_key_enabled(&switch_to_cond_stibp))

arch/x86/kernel/process.h

@@ -19,7 +19,7 @@ static inline void switch_to_extra(struct task_struct *prev,
 	if (IS_ENABLED(CONFIG_SMP)) {
 		/*
 		 * Avoid __switch_to_xtra() invocation when conditional
-		 * STIPB is disabled and the only different bit is
+		 * STIBP is disabled and the only different bit is
 		 * TIF_SPEC_IB. For CONFIG_SMP=n TIF_SPEC_IB is not
 		 * in the TIF_WORK_CTXSW masks.
 		 */

arch/x86/mm/init.c

@@ -931,7 +931,7 @@ unsigned long max_swapfile_size(void)
 
 	pages = generic_max_swapfile_size();
 
-	if (boot_cpu_has_bug(X86_BUG_L1TF)) {
+	if (boot_cpu_has_bug(X86_BUG_L1TF) && l1tf_mitigation != L1TF_MITIGATION_OFF) {
 		/* Limit the swap file size to MAX_PA/2 for L1TF workaround */
 		unsigned long long l1tf_limit = l1tf_pfn_limit();
 		/*