Merge branch 'speck-v20' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Merge speculative store buffer bypass fixes from Thomas Gleixner:

 - rework of the SPEC_CTRL MSR management to accomodate the new fancy
   SSBD (Speculative Store Bypass Disable) bit handling.

 - the CPU bug and sysfs infrastructure for the exciting new Speculative
   Store Bypass 'feature'.

 - support for disabling SSB via LS_CFG MSR on AMD CPUs including
   Hyperthread synchronization on ZEN.

 - PRCTL support for dynamic runtime control of SSB

 - SECCOMP integration to automatically disable SSB for sandboxed
   processes with a filter flag for opt-out.

 - KVM integration to allow guests fiddling with SSBD including the new
   software MSR VIRT_SPEC_CTRL to handle the LS_CFG based oddities on
   AMD.

 - BPF protection against SSB

.. this is just the core and x86 side, other architecture support will
come separately.

* 'speck-v20' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (49 commits)
  bpf: Prevent memory disambiguation attack
  x86/bugs: Rename SSBD_NO to SSB_NO
  KVM: SVM: Implement VIRT_SPEC_CTRL support for SSBD
  x86/speculation, KVM: Implement support for VIRT_SPEC_CTRL/LS_CFG
  x86/bugs: Rework spec_ctrl base and mask logic
  x86/bugs: Remove x86_spec_ctrl_set()
  x86/bugs: Expose x86_spec_ctrl_base directly
  x86/bugs: Unify x86_spec_ctrl_{set_guest,restore_host}
  x86/speculation: Rework speculative_store_bypass_update()
  x86/speculation: Add virtualized speculative store bypass disable support
  x86/bugs, KVM: Extend speculation control for VIRT_SPEC_CTRL
  x86/speculation: Handle HT correctly on AMD
  x86/cpufeatures: Add FEATURE_ZEN
  x86/cpufeatures: Disentangle SSBD enumeration
  x86/cpufeatures: Disentangle MSR_SPEC_CTRL enumeration from IBRS
  x86/speculation: Use synthetic bits for IBRS/IBPB/STIBP
  KVM: SVM: Move spec control call after restore of GS
  x86/cpu: Make alternative_msr_write work for 32-bit code
  x86/bugs: Fix the parameters alignment and missing void
  x86/bugs: Make cpu_show_common() static
  ...

7 files changed, 621 insertions, 31 deletions

diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index 12bc0a1139da..1b18be3f35a8 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -10,6 +10,7 @@
 #include <asm/processor.h>
 #include <asm/apic.h>
 #include <asm/cpu.h>
+#include <asm/spec-ctrl.h>
 #include <asm/smp.h>
 #include <asm/pci-direct.h>
 #include <asm/delay.h>
@@ -554,6 +555,26 @@ static void bsp_init_amd(struct cpuinfo_x86 *c)
 		rdmsrl(MSR_FAM10H_NODE_ID, value);
 		nodes_per_socket = ((value >> 3) & 7) + 1;
 	}
+
+	if (c->x86 >= 0x15 && c->x86 <= 0x17) {
+		unsigned int bit;
+
+		switch (c->x86) {
+		case 0x15: bit = 54; break;
+		case 0x16: bit = 33; break;
+		case 0x17: bit = 10; break;
+		default: return;
+		}
+		/*
+		 * Try to cache the base value so further operations can
+		 * avoid RMW. If that faults, do not enable SSBD.
+		 */
+		if (!rdmsrl_safe(MSR_AMD64_LS_CFG, &x86_amd_ls_cfg_base)) {
+			setup_force_cpu_cap(X86_FEATURE_LS_CFG_SSBD);
+			setup_force_cpu_cap(X86_FEATURE_SSBD);
+			x86_amd_ls_cfg_ssbd_mask = 1ULL << bit;
+		}
+	}
 }
 
 static void early_detect_mem_encrypt(struct cpuinfo_x86 *c)
@@ -791,6 +812,7 @@ static void init_amd_bd(struct cpuinfo_x86 *c)
 
 static void init_amd_zn(struct cpuinfo_x86 *c)
 {
+	set_cpu_cap(c, X86_FEATURE_ZEN);
 	/*
 	 * Fix erratum 1076: CPB feature bit not being set in CPUID. It affects
 	 * all up to and including B1.
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index bfca937bdcc3..7416fc206b4a 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -12,8 +12,10 @@
 #include <linux/utsname.h>
 #include <linux/cpu.h>
 #include <linux/module.h>
+#include <linux/nospec.h>
+#include <linux/prctl.h>
 
-#include <asm/nospec-branch.h>
+#include <asm/spec-ctrl.h>
 #include <asm/cmdline.h>
 #include <asm/bugs.h>
 #include <asm/processor.h>
@@ -27,6 +29,27 @@
 #include <asm/intel-family.h>
 
 static void __init spectre_v2_select_mitigation(void);
+static void __init ssb_select_mitigation(void);
+
+/*
+ * Our boot-time value of the SPEC_CTRL MSR. We read it once so that any
+ * writes to SPEC_CTRL contain whatever reserved bits have been set.
+ */
+u64 __ro_after_init x86_spec_ctrl_base;
+EXPORT_SYMBOL_GPL(x86_spec_ctrl_base);
+
+/*
+ * The vendor and possibly platform specific bits which can be modified in
+ * x86_spec_ctrl_base.
+ */
+static u64 __ro_after_init x86_spec_ctrl_mask = SPEC_CTRL_IBRS;
+
+/*
+ * AMD specific MSR info for Speculative Store Bypass control.
+ * x86_amd_ls_cfg_ssbd_mask is initialized in identify_boot_cpu().
+ */
+u64 __ro_after_init x86_amd_ls_cfg_base;
+u64 __ro_after_init x86_amd_ls_cfg_ssbd_mask;
 
 void __init check_bugs(void)
 {
@@ -37,9 +60,27 @@ void __init check_bugs(void)
 		print_cpu_info(&boot_cpu_data);
 	}
 
+	/*
+	 * Read the SPEC_CTRL MSR to account for reserved bits which may
+	 * have unknown values. AMD64_LS_CFG MSR is cached in the early AMD
+	 * init code as it is not enumerated and depends on the family.
+	 */
+	if (boot_cpu_has(X86_FEATURE_MSR_SPEC_CTRL))
+		rdmsrl(MSR_IA32_SPEC_CTRL, x86_spec_ctrl_base);
+
+	/* Allow STIBP in MSR_SPEC_CTRL if supported */
+	if (boot_cpu_has(X86_FEATURE_STIBP))
+		x86_spec_ctrl_mask |= SPEC_CTRL_STIBP;
+
 	/* Select the proper spectre mitigation before patching alternatives */
 	spectre_v2_select_mitigation();
 
+	/*
+	 * Select proper mitigation for any exposure to the Speculative Store
+	 * Bypass vulnerability.
+	 */
+	ssb_select_mitigation();
+
 #ifdef CONFIG_X86_32
 	/*
 	 * Check whether we are able to run this kernel safely on SMP.
@@ -93,7 +134,76 @@ static const char *spectre_v2_strings[] = {
 #undef pr_fmt
 #define pr_fmt(fmt)     "Spectre V2 : " fmt
 
-static enum spectre_v2_mitigation spectre_v2_enabled = SPECTRE_V2_NONE;
+static enum spectre_v2_mitigation spectre_v2_enabled __ro_after_init =
+	SPECTRE_V2_NONE;
+
+void
+x86_virt_spec_ctrl(u64 guest_spec_ctrl, u64 guest_virt_spec_ctrl, bool setguest)
+{
+	u64 msrval, guestval, hostval = x86_spec_ctrl_base;
+	struct thread_info *ti = current_thread_info();
+
+	/* Is MSR_SPEC_CTRL implemented ? */
+	if (static_cpu_has(X86_FEATURE_MSR_SPEC_CTRL)) {
+		/*
+		 * Restrict guest_spec_ctrl to supported values. Clear the
+		 * modifiable bits in the host base value and or the
+		 * modifiable bits from the guest value.
+		 */
+		guestval = hostval & ~x86_spec_ctrl_mask;
+		guestval |= guest_spec_ctrl & x86_spec_ctrl_mask;
+
+		/* SSBD controlled in MSR_SPEC_CTRL */
+		if (static_cpu_has(X86_FEATURE_SPEC_CTRL_SSBD))
+			hostval |= ssbd_tif_to_spec_ctrl(ti->flags);
+
+		if (hostval != guestval) {
+			msrval = setguest ? guestval : hostval;
+			wrmsrl(MSR_IA32_SPEC_CTRL, msrval);
+		}
+	}
+
+	/*
+	 * If SSBD is not handled in MSR_SPEC_CTRL on AMD, update
+	 * MSR_AMD64_L2_CFG or MSR_VIRT_SPEC_CTRL if supported.
+	 */
+	if (!static_cpu_has(X86_FEATURE_LS_CFG_SSBD) &&
+	    !static_cpu_has(X86_FEATURE_VIRT_SSBD))
+		return;
+
+	/*
+	 * If the host has SSBD mitigation enabled, force it in the host's
+	 * virtual MSR value. If its not permanently enabled, evaluate
+	 * current's TIF_SSBD thread flag.
+	 */
+	if (static_cpu_has(X86_FEATURE_SPEC_STORE_BYPASS_DISABLE))
+		hostval = SPEC_CTRL_SSBD;
+	else
+		hostval = ssbd_tif_to_spec_ctrl(ti->flags);
+
+	/* Sanitize the guest value */
+	guestval = guest_virt_spec_ctrl & SPEC_CTRL_SSBD;
+
+	if (hostval != guestval) {
+		unsigned long tif;
+
+		tif = setguest ? ssbd_spec_ctrl_to_tif(guestval) :
+				 ssbd_spec_ctrl_to_tif(hostval);
+
+		speculative_store_bypass_update(tif);
+	}
+}
+EXPORT_SYMBOL_GPL(x86_virt_spec_ctrl);
+
+static void x86_amd_ssb_disable(void)
+{
+	u64 msrval = x86_amd_ls_cfg_base | x86_amd_ls_cfg_ssbd_mask;
+
+	if (boot_cpu_has(X86_FEATURE_VIRT_SSBD))
+		wrmsrl(MSR_AMD64_VIRT_SPEC_CTRL, SPEC_CTRL_SSBD);
+	else if (boot_cpu_has(X86_FEATURE_LS_CFG_SSBD))
+		wrmsrl(MSR_AMD64_LS_CFG, msrval);
+}
 
 #ifdef RETPOLINE
 static bool spectre_v2_bad_module;
@@ -312,32 +422,289 @@ retpoline_auto:
 }
 
 #undef pr_fmt
+#define pr_fmt(fmt)	"Speculative Store Bypass: " fmt
+
+static enum ssb_mitigation ssb_mode __ro_after_init = SPEC_STORE_BYPASS_NONE;
+
+/* The kernel command line selection */
+enum ssb_mitigation_cmd {
+	SPEC_STORE_BYPASS_CMD_NONE,
+	SPEC_STORE_BYPASS_CMD_AUTO,
+	SPEC_STORE_BYPASS_CMD_ON,
+	SPEC_STORE_BYPASS_CMD_PRCTL,
+	SPEC_STORE_BYPASS_CMD_SECCOMP,
+};
+
+static const char *ssb_strings[] = {
+	[SPEC_STORE_BYPASS_NONE]	= "Vulnerable",
+	[SPEC_STORE_BYPASS_DISABLE]	= "Mitigation: Speculative Store Bypass disabled",
+	[SPEC_STORE_BYPASS_PRCTL]	= "Mitigation: Speculative Store Bypass disabled via prctl",
+	[SPEC_STORE_BYPASS_SECCOMP]	= "Mitigation: Speculative Store Bypass disabled via prctl and seccomp",
+};
+
+static const struct {
+	const char *option;
+	enum ssb_mitigation_cmd cmd;
+} ssb_mitigation_options[] = {
+	{ "auto",	SPEC_STORE_BYPASS_CMD_AUTO },    /* Platform decides */
+	{ "on",		SPEC_STORE_BYPASS_CMD_ON },      /* Disable Speculative Store Bypass */
+	{ "off",	SPEC_STORE_BYPASS_CMD_NONE },    /* Don't touch Speculative Store Bypass */
+	{ "prctl",	SPEC_STORE_BYPASS_CMD_PRCTL },   /* Disable Speculative Store Bypass via prctl */
+	{ "seccomp",	SPEC_STORE_BYPASS_CMD_SECCOMP }, /* Disable Speculative Store Bypass via prctl and seccomp */
+};
+
+static enum ssb_mitigation_cmd __init ssb_parse_cmdline(void)
+{
+	enum ssb_mitigation_cmd cmd = SPEC_STORE_BYPASS_CMD_AUTO;
+	char arg[20];
+	int ret, i;
+
+	if (cmdline_find_option_bool(boot_command_line, "nospec_store_bypass_disable")) {
+		return SPEC_STORE_BYPASS_CMD_NONE;
+	} else {
+		ret = cmdline_find_option(boot_command_line, "spec_store_bypass_disable",
+					  arg, sizeof(arg));
+		if (ret < 0)
+			return SPEC_STORE_BYPASS_CMD_AUTO;
+
+		for (i = 0; i < ARRAY_SIZE(ssb_mitigation_options); i++) {
+			if (!match_option(arg, ret, ssb_mitigation_options[i].option))
+				continue;
+
+			cmd = ssb_mitigation_options[i].cmd;
+			break;
+		}
+
+		if (i >= ARRAY_SIZE(ssb_mitigation_options)) {
+			pr_err("unknown option (%s). Switching to AUTO select\n", arg);
+			return SPEC_STORE_BYPASS_CMD_AUTO;
+		}
+	}
+
+	return cmd;
+}
+
+static enum ssb_mitigation __init __ssb_select_mitigation(void)
+{
+	enum ssb_mitigation mode = SPEC_STORE_BYPASS_NONE;
+	enum ssb_mitigation_cmd cmd;
+
+	if (!boot_cpu_has(X86_FEATURE_SSBD))
+		return mode;
+
+	cmd = ssb_parse_cmdline();
+	if (!boot_cpu_has_bug(X86_BUG_SPEC_STORE_BYPASS) &&
+	    (cmd == SPEC_STORE_BYPASS_CMD_NONE ||
+	     cmd == SPEC_STORE_BYPASS_CMD_AUTO))
+		return mode;
+
+	switch (cmd) {
+	case SPEC_STORE_BYPASS_CMD_AUTO:
+	case SPEC_STORE_BYPASS_CMD_SECCOMP:
+		/*
+		 * Choose prctl+seccomp as the default mode if seccomp is
+		 * enabled.
+		 */
+		if (IS_ENABLED(CONFIG_SECCOMP))
+			mode = SPEC_STORE_BYPASS_SECCOMP;
+		else
+			mode = SPEC_STORE_BYPASS_PRCTL;
+		break;
+	case SPEC_STORE_BYPASS_CMD_ON:
+		mode = SPEC_STORE_BYPASS_DISABLE;
+		break;
+	case SPEC_STORE_BYPASS_CMD_PRCTL:
+		mode = SPEC_STORE_BYPASS_PRCTL;
+		break;
+	case SPEC_STORE_BYPASS_CMD_NONE:
+		break;
+	}
+
+	/*
+	 * We have three CPU feature flags that are in play here:
+	 *  - X86_BUG_SPEC_STORE_BYPASS - CPU is susceptible.
+	 *  - X86_FEATURE_SSBD - CPU is able to turn off speculative store bypass
+	 *  - X86_FEATURE_SPEC_STORE_BYPASS_DISABLE - engage the mitigation
+	 */
+	if (mode == SPEC_STORE_BYPASS_DISABLE) {
+		setup_force_cpu_cap(X86_FEATURE_SPEC_STORE_BYPASS_DISABLE);
+		/*
+		 * Intel uses the SPEC CTRL MSR Bit(2) for this, while AMD uses
+		 * a completely different MSR and bit dependent on family.
+		 */
+		switch (boot_cpu_data.x86_vendor) {
+		case X86_VENDOR_INTEL:
+			x86_spec_ctrl_base |= SPEC_CTRL_SSBD;
+			x86_spec_ctrl_mask |= SPEC_CTRL_SSBD;
+			wrmsrl(MSR_IA32_SPEC_CTRL, x86_spec_ctrl_base);
+			break;
+		case X86_VENDOR_AMD:
+			x86_amd_ssb_disable();
+			break;
+		}
+	}
+
+	return mode;
+}
+
+static void ssb_select_mitigation(void)
+{
+	ssb_mode = __ssb_select_mitigation();
+
+	if (boot_cpu_has_bug(X86_BUG_SPEC_STORE_BYPASS))
+		pr_info("%s\n", ssb_strings[ssb_mode]);
+}
+
+#undef pr_fmt
+#define pr_fmt(fmt)     "Speculation prctl: " fmt
+
+static int ssb_prctl_set(struct task_struct *task, unsigned long ctrl)
+{
+	bool update;
+
+	if (ssb_mode != SPEC_STORE_BYPASS_PRCTL &&
+	    ssb_mode != SPEC_STORE_BYPASS_SECCOMP)
+		return -ENXIO;
+
+	switch (ctrl) {
+	case PR_SPEC_ENABLE:
+		/* If speculation is force disabled, enable is not allowed */
+		if (task_spec_ssb_force_disable(task))
+			return -EPERM;
+		task_clear_spec_ssb_disable(task);
+		update = test_and_clear_tsk_thread_flag(task, TIF_SSBD);
+		break;
+	case PR_SPEC_DISABLE:
+		task_set_spec_ssb_disable(task);
+		update = !test_and_set_tsk_thread_flag(task, TIF_SSBD);
+		break;
+	case PR_SPEC_FORCE_DISABLE:
+		task_set_spec_ssb_disable(task);
+		task_set_spec_ssb_force_disable(task);
+		update = !test_and_set_tsk_thread_flag(task, TIF_SSBD);
+		break;
+	default:
+		return -ERANGE;
+	}
+
+	/*
+	 * If being set on non-current task, delay setting the CPU
+	 * mitigation until it is next scheduled.
+	 */
+	if (task == current && update)
+		speculative_store_bypass_update_current();
+
+	return 0;
+}
+
+int arch_prctl_spec_ctrl_set(struct task_struct *task, unsigned long which,
+			     unsigned long ctrl)
+{
+	switch (which) {
+	case PR_SPEC_STORE_BYPASS:
+		return ssb_prctl_set(task, ctrl);
+	default:
+		return -ENODEV;
+	}
+}
+
+#ifdef CONFIG_SECCOMP
+void arch_seccomp_spec_mitigate(struct task_struct *task)
+{
+	if (ssb_mode == SPEC_STORE_BYPASS_SECCOMP)
+		ssb_prctl_set(task, PR_SPEC_FORCE_DISABLE);
+}
+#endif
+
+static int ssb_prctl_get(struct task_struct *task)
+{
+	switch (ssb_mode) {
+	case SPEC_STORE_BYPASS_DISABLE:
+		return PR_SPEC_DISABLE;
+	case SPEC_STORE_BYPASS_SECCOMP:
+	case SPEC_STORE_BYPASS_PRCTL:
+		if (task_spec_ssb_force_disable(task))
+			return PR_SPEC_PRCTL | PR_SPEC_FORCE_DISABLE;
+		if (task_spec_ssb_disable(task))
+			return PR_SPEC_PRCTL | PR_SPEC_DISABLE;
+		return PR_SPEC_PRCTL | PR_SPEC_ENABLE;
+	default:
+		if (boot_cpu_has_bug(X86_BUG_SPEC_STORE_BYPASS))
+			return PR_SPEC_ENABLE;
+		return PR_SPEC_NOT_AFFECTED;
+	}
+}
+
+int arch_prctl_spec_ctrl_get(struct task_struct *task, unsigned long which)
+{
+	switch (which) {
+	case PR_SPEC_STORE_BYPASS:
+		return ssb_prctl_get(task);
+	default:
+		return -ENODEV;
+	}
+}
+
+void x86_spec_ctrl_setup_ap(void)
+{
+	if (boot_cpu_has(X86_FEATURE_MSR_SPEC_CTRL))
+		wrmsrl(MSR_IA32_SPEC_CTRL, x86_spec_ctrl_base);
+
+	if (ssb_mode == SPEC_STORE_BYPASS_DISABLE)
+		x86_amd_ssb_disable();
+}
 
 #ifdef CONFIG_SYSFS
-ssize_t cpu_show_meltdown(struct device *dev, struct device_attribute *attr, char *buf)
+
+static ssize_t cpu_show_common(struct device *dev, struct device_attribute *attr,
+			       char *buf, unsigned int bug)
 {
-	if (!boot_cpu_has_bug(X86_BUG_CPU_MELTDOWN))
+	if (!boot_cpu_has_bug(bug))
 		return sprintf(buf, "Not affected\n");
-	if (boot_cpu_has(X86_FEATURE_PTI))
-		return sprintf(buf, "Mitigation: PTI\n");
+
+	switch (bug) {
+	case X86_BUG_CPU_MELTDOWN:
+		if (boot_cpu_has(X86_FEATURE_PTI))
+			return sprintf(buf, "Mitigation: PTI\n");
+
+		break;
+
+	case X86_BUG_SPECTRE_V1:
+		return sprintf(buf, "Mitigation: __user pointer sanitization\n");
+
+	case X86_BUG_SPECTRE_V2:
+		return sprintf(buf, "%s%s%s%s\n", spectre_v2_strings[spectre_v2_enabled],
+			       boot_cpu_has(X86_FEATURE_USE_IBPB) ? ", IBPB" : "",
+			       boot_cpu_has(X86_FEATURE_USE_IBRS_FW) ? ", IBRS_FW" : "",
+			       spectre_v2_module_string());
+
+	case X86_BUG_SPEC_STORE_BYPASS:
+		return sprintf(buf, "%s\n", ssb_strings[ssb_mode]);
+
+	default:
+		break;
+	}
+
 	return sprintf(buf, "Vulnerable\n");
 }
 
+ssize_t cpu_show_meltdown(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	return cpu_show_common(dev, attr, buf, X86_BUG_CPU_MELTDOWN);
+}
+
 ssize_t cpu_show_spectre_v1(struct device *dev, struct device_attribute *attr, char *buf)
 {
-	if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V1))
-		return sprintf(buf, "Not affected\n");
-	return sprintf(buf, "Mitigation: __user pointer sanitization\n");
+	return cpu_show_common(dev, attr, buf, X86_BUG_SPECTRE_V1);
 }
 
 ssize_t cpu_show_spectre_v2(struct device *dev, struct device_attribute *attr, char *buf)
 {
-	if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V2))
-		return sprintf(buf, "Not affected\n");
+	return cpu_show_common(dev, attr, buf, X86_BUG_SPECTRE_V2);
+}
 
-	return sprintf(buf, "%s%s%s%s\n", spectre_v2_strings[spectre_v2_enabled],
-		       boot_cpu_has(X86_FEATURE_USE_IBPB) ? ", IBPB" : "",
-		       boot_cpu_has(X86_FEATURE_USE_IBRS_FW) ? ", IBRS_FW" : "",
-		       spectre_v2_module_string());
+ssize_t cpu_show_spec_store_bypass(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	return cpu_show_common(dev, attr, buf, X86_BUG_SPEC_STORE_BYPASS);
 }
 #endif
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index ce243f7d2d4e..78decc3e3067 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -757,17 +757,32 @@ static void init_speculation_control(struct cpuinfo_x86 *c)
 	 * and they also have a different bit for STIBP support. Also,
 	 * a hypervisor might have set the individual AMD bits even on
 	 * Intel CPUs, for finer-grained selection of what's available.
-	 *
-	 * We use the AMD bits in 0x8000_0008 EBX as the generic hardware
-	 * features, which are visible in /proc/cpuinfo and used by the
-	 * kernel. So set those accordingly from the Intel bits.
 	 */
 	if (cpu_has(c, X86_FEATURE_SPEC_CTRL)) {
 		set_cpu_cap(c, X86_FEATURE_IBRS);
 		set_cpu_cap(c, X86_FEATURE_IBPB);
+		set_cpu_cap(c, X86_FEATURE_MSR_SPEC_CTRL);
 	}
+
 	if (cpu_has(c, X86_FEATURE_INTEL_STIBP))
 		set_cpu_cap(c, X86_FEATURE_STIBP);
+
+	if (cpu_has(c, X86_FEATURE_SPEC_CTRL_SSBD) ||
+	    cpu_has(c, X86_FEATURE_VIRT_SSBD))
+		set_cpu_cap(c, X86_FEATURE_SSBD);
+
+	if (cpu_has(c, X86_FEATURE_AMD_IBRS)) {
+		set_cpu_cap(c, X86_FEATURE_IBRS);
+		set_cpu_cap(c, X86_FEATURE_MSR_SPEC_CTRL);
+	}
+
+	if (cpu_has(c, X86_FEATURE_AMD_IBPB))
+		set_cpu_cap(c, X86_FEATURE_IBPB);
+
+	if (cpu_has(c, X86_FEATURE_AMD_STIBP)) {
+		set_cpu_cap(c, X86_FEATURE_STIBP);
+		set_cpu_cap(c, X86_FEATURE_MSR_SPEC_CTRL);
+	}
 }
 
 void get_cpu_cap(struct cpuinfo_x86 *c)
@@ -927,21 +942,55 @@ static const __initconst struct x86_cpu_id cpu_no_meltdown[] = {
 	{}
 };
 
-static bool __init cpu_vulnerable_to_meltdown(struct cpuinfo_x86 *c)
+static const __initconst struct x86_cpu_id cpu_no_spec_store_bypass[] = {
+	{ X86_VENDOR_INTEL,	6,	INTEL_FAM6_ATOM_PINEVIEW	},
+	{ X86_VENDOR_INTEL,	6,	INTEL_FAM6_ATOM_LINCROFT	},
+	{ X86_VENDOR_INTEL,	6,	INTEL_FAM6_ATOM_PENWELL		},
+	{ X86_VENDOR_INTEL,	6,	INTEL_FAM6_ATOM_CLOVERVIEW	},
+	{ X86_VENDOR_INTEL,	6,	INTEL_FAM6_ATOM_CEDARVIEW	},
+	{ X86_VENDOR_INTEL,	6,	INTEL_FAM6_ATOM_SILVERMONT1	},
+	{ X86_VENDOR_INTEL,	6,	INTEL_FAM6_ATOM_AIRMONT		},
+	{ X86_VENDOR_INTEL,	6,	INTEL_FAM6_ATOM_SILVERMONT2	},
+	{ X86_VENDOR_INTEL,	6,	INTEL_FAM6_ATOM_MERRIFIELD	},
+	{ X86_VENDOR_INTEL,	6,	INTEL_FAM6_CORE_YONAH		},
+	{ X86_VENDOR_INTEL,	6,	INTEL_FAM6_XEON_PHI_KNL		},
+	{ X86_VENDOR_INTEL,	6,	INTEL_FAM6_XEON_PHI_KNM		},
+	{ X86_VENDOR_CENTAUR,	5,					},
+	{ X86_VENDOR_INTEL,	5,					},
+	{ X86_VENDOR_NSC,	5,					},
+	{ X86_VENDOR_AMD,	0x12,					},
+	{ X86_VENDOR_AMD,	0x11,					},
+	{ X86_VENDOR_AMD,	0x10,					},
+	{ X86_VENDOR_AMD,	0xf,					},
+	{ X86_VENDOR_ANY,	4,					},
+	{}
+};
+
+static void __init cpu_set_bug_bits(struct cpuinfo_x86 *c)
 {
 	u64 ia32_cap = 0;
 
-	if (x86_match_cpu(cpu_no_meltdown))
-		return false;
-
 	if (cpu_has(c, X86_FEATURE_ARCH_CAPABILITIES))
 		rdmsrl(MSR_IA32_ARCH_CAPABILITIES, ia32_cap);
 
+	if (!x86_match_cpu(cpu_no_spec_store_bypass) &&
+	   !(ia32_cap & ARCH_CAP_SSB_NO))
+		setup_force_cpu_bug(X86_BUG_SPEC_STORE_BYPASS);
+
+	if (x86_match_cpu(cpu_no_speculation))
+		return;
+
+	setup_force_cpu_bug(X86_BUG_SPECTRE_V1);
+	setup_force_cpu_bug(X86_BUG_SPECTRE_V2);
+
+	if (x86_match_cpu(cpu_no_meltdown))
+		return;
+
 	/* Rogue Data Cache Load? No! */
 	if (ia32_cap & ARCH_CAP_RDCL_NO)
-		return false;
+		return;
 
-	return true;
+	setup_force_cpu_bug(X86_BUG_CPU_MELTDOWN);
 }
 
 /*
@@ -992,12 +1041,7 @@ static void __init early_identify_cpu(struct cpuinfo_x86 *c)
 
 	setup_force_cpu_cap(X86_FEATURE_ALWAYS);
 
-	if (!x86_match_cpu(cpu_no_speculation)) {
-		if (cpu_vulnerable_to_meltdown(c))
-			setup_force_cpu_bug(X86_BUG_CPU_MELTDOWN);
-		setup_force_cpu_bug(X86_BUG_SPECTRE_V1);
-		setup_force_cpu_bug(X86_BUG_SPECTRE_V2);
-	}
+	cpu_set_bug_bits(c);
 
 	fpu__init_system(c);
 
@@ -1359,6 +1403,7 @@ void identify_secondary_cpu(struct cpuinfo_x86 *c)
 #endif
 	mtrr_ap_init();
 	validate_apic_and_package_id(c);
+	x86_spec_ctrl_setup_ap();
 }
 
 static __init int setup_noclflush(char *arg)
diff --git a/arch/x86/kernel/cpu/cpu.h b/arch/x86/kernel/cpu/cpu.h
index e806b11a99af..37672d299e35 100644
--- a/arch/x86/kernel/cpu/cpu.h
+++ b/arch/x86/kernel/cpu/cpu.h
@@ -50,4 +50,6 @@ extern void cpu_detect_cache_sizes(struct cpuinfo_x86 *c);
 
 unsigned int aperfmperf_get_khz(int cpu);
 
+extern void x86_spec_ctrl_setup_ap(void);
+
 #endif /* ARCH_X86_CPU_H */
diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
index 60d1897041da..577e7f7ae273 100644
--- a/arch/x86/kernel/cpu/intel.c
+++ b/arch/x86/kernel/cpu/intel.c
@@ -188,7 +188,10 @@ static void early_init_intel(struct cpuinfo_x86 *c)
 		setup_clear_cpu_cap(X86_FEATURE_IBPB);
 		setup_clear_cpu_cap(X86_FEATURE_STIBP);
 		setup_clear_cpu_cap(X86_FEATURE_SPEC_CTRL);
+		setup_clear_cpu_cap(X86_FEATURE_MSR_SPEC_CTRL);
 		setup_clear_cpu_cap(X86_FEATURE_INTEL_STIBP);
+		setup_clear_cpu_cap(X86_FEATURE_SSBD);
+		setup_clear_cpu_cap(X86_FEATURE_SPEC_CTRL_SSBD);
 	}
 
 	/*
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 03408b942adb..30ca2d1a9231 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -38,6 +38,7 @@
 #include <asm/switch_to.h>
 #include <asm/desc.h>
 #include <asm/prctl.h>
+#include <asm/spec-ctrl.h>
 
 /*
  * per-CPU TSS segments. Threads are completely 'soft' on Linux,
@@ -278,6 +279,148 @@ static inline void switch_to_bitmap(struct tss_struct *tss,
 	}
 }
 
+#ifdef CONFIG_SMP
+
+struct ssb_state {
+	struct ssb_state	*shared_state;
+	raw_spinlock_t		lock;
+	unsigned int		disable_state;
+	unsigned long		local_state;
+};
+
+#define LSTATE_SSB	0
+
+static DEFINE_PER_CPU(struct ssb_state, ssb_state);
+
+void speculative_store_bypass_ht_init(void)
+{
+	struct ssb_state *st = this_cpu_ptr(&ssb_state);
+	unsigned int this_cpu = smp_processor_id();
+	unsigned int cpu;
+
+	st->local_state = 0;
+
+	/*
+	 * Shared state setup happens once on the first bringup
+	 * of the CPU. It's not destroyed on CPU hotunplug.
+	 */
+	if (st->shared_state)
+		return;
+
+	raw_spin_lock_init(&st->lock);
+
+	/*
+	 * Go over HT siblings and check whether one of them has set up the
+	 * shared state pointer already.
+	 */
+	for_each_cpu(cpu, topology_sibling_cpumask(this_cpu)) {
+		if (cpu == this_cpu)
+			continue;
+
+		if (!per_cpu(ssb_state, cpu).shared_state)
+			continue;
+
+		/* Link it to the state of the sibling: */
+		st->shared_state = per_cpu(ssb_state, cpu).shared_state;
+		return;
+	}
+
+	/*
+	 * First HT sibling to come up on the core.  Link shared state of
+	 * the first HT sibling to itself. The siblings on the same core
+	 * which come up later will see the shared state pointer and link
+	 * themself to the state of this CPU.
+	 */
+	st->shared_state = st;
+}
+
+/*
+ * Logic is: First HT sibling enables SSBD for both siblings in the core
+ * and last sibling to disable it, disables it for the whole core. This how
+ * MSR_SPEC_CTRL works in "hardware":
+ *
+ *  CORE_SPEC_CTRL = THREAD0_SPEC_CTRL | THREAD1_SPEC_CTRL
+ */
+static __always_inline void amd_set_core_ssb_state(unsigned long tifn)
+{
+	struct ssb_state *st = this_cpu_ptr(&ssb_state);
+	u64 msr = x86_amd_ls_cfg_base;
+
+	if (!static_cpu_has(X86_FEATURE_ZEN)) {
+		msr |= ssbd_tif_to_amd_ls_cfg(tifn);
+		wrmsrl(MSR_AMD64_LS_CFG, msr);
+		return;
+	}
+
+	if (tifn & _TIF_SSBD) {
+		/*
+		 * Since this can race with prctl(), block reentry on the
+		 * same CPU.
+		 */
+		if (__test_and_set_bit(LSTATE_SSB, &st->local_state))
+			return;
+
+		msr |= x86_amd_ls_cfg_ssbd_mask;
+
+		raw_spin_lock(&st->shared_state->lock);
+		/* First sibling enables SSBD: */
+		if (!st->shared_state->disable_state)
+			wrmsrl(MSR_AMD64_LS_CFG, msr);
+		st->shared_state->disable_state++;
+		raw_spin_unlock(&st->shared_state->lock);
+	} else {
+		if (!__test_and_clear_bit(LSTATE_SSB, &st->local_state))
+			return;
+
+		raw_spin_lock(&st->shared_state->lock);
+		st->shared_state->disable_state--;
+		if (!st->shared_state->disable_state)
+			wrmsrl(MSR_AMD64_LS_CFG, msr);
+		raw_spin_unlock(&st->shared_state->lock);
+	}
+}
+#else
+static __always_inline void amd_set_core_ssb_state(unsigned long tifn)
+{
+	u64 msr = x86_amd_ls_cfg_base | ssbd_tif_to_amd_ls_cfg(tifn);
+
+	wrmsrl(MSR_AMD64_LS_CFG, msr);
+}
+#endif
+
+static __always_inline void amd_set_ssb_virt_state(unsigned long tifn)
+{
+	/*
+	 * SSBD has the same definition in SPEC_CTRL and VIRT_SPEC_CTRL,
+	 * so ssbd_tif_to_spec_ctrl() just works.
+	 */
+	wrmsrl(MSR_AMD64_VIRT_SPEC_CTRL, ssbd_tif_to_spec_ctrl(tifn));
+}
+
+static __always_inline void intel_set_ssb_state(unsigned long tifn)
+{
+	u64 msr = x86_spec_ctrl_base | ssbd_tif_to_spec_ctrl(tifn);
+
+	wrmsrl(MSR_IA32_SPEC_CTRL, msr);
+}
+
+static __always_inline void __speculative_store_bypass_update(unsigned long tifn)
+{
+	if (static_cpu_has(X86_FEATURE_VIRT_SSBD))
+		amd_set_ssb_virt_state(tifn);
+	else if (static_cpu_has(X86_FEATURE_LS_CFG_SSBD))
+		amd_set_core_ssb_state(tifn);
+	else
+		intel_set_ssb_state(tifn);
+}
+
+void speculative_store_bypass_update(unsigned long tif)
+{
+	preempt_disable();
+	__speculative_store_bypass_update(tif);
+	preempt_enable();
+}
+
 void __switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p,
 		      struct tss_struct *tss)
 {
@@ -309,6 +452,9 @@ void __switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p,
 
 	if ((tifp ^ tifn) & _TIF_NOCPUID)
 		set_cpuid_faulting(!!(tifn & _TIF_NOCPUID));
+
+	if ((tifp ^ tifn) & _TIF_SSBD)
+		__speculative_store_bypass_update(tifn);
 }
 
 /*
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 0f1cbb042f49..9dd324ae4832 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -79,6 +79,7 @@
 #include <asm/qspinlock.h>
 #include <asm/intel-family.h>
 #include <asm/cpu_device_id.h>
+#include <asm/spec-ctrl.h>
 
 /* Number of siblings per CPU package */
 int smp_num_siblings = 1;
@@ -244,6 +245,8 @@ static void notrace start_secondary(void *unused)
 	 */
 	check_tsc_sync_target();
 
+	speculative_store_bypass_ht_init();
+
 	/*
 	 * Lock vector_lock, set CPU online and bring the vector
 	 * allocator online. Online must be set with vector_lock held
@@ -1292,6 +1295,8 @@ void __init native_smp_prepare_cpus(unsigned int max_cpus)
 	set_mtrr_aps_delayed_init();
 
 	smp_quirk_init_udelay();
+
+	speculative_store_bypass_ht_init();
 }
 
 void arch_enable_nonboot_cpus_begin(void)