x86/litf: Introduce vmx status variable

Store the effective mitigation of VMX in a status variable and use it to
report the VMX state in the l1tf sysfs file.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Jiri Kosina <jkosina@suse.cz>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lkml.kernel.org/r/20180713142322.433098358@linutronix.de

CVE-2018-3620
CVE-2018-3646

[smb: Minor context adjustment in last hunk]
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

arch/x86/include/asm/vmx.h

@@ -500,4 +500,13 @@ enum vm_instruction_error_number {
 	VMXERR_INVALID_OPERAND_TO_INVEPT_INVVPID = 28,
 };
 
+enum vmx_l1d_flush_state {
+	VMENTER_L1D_FLUSH_AUTO,
+	VMENTER_L1D_FLUSH_NEVER,
+	VMENTER_L1D_FLUSH_COND,
+	VMENTER_L1D_FLUSH_ALWAYS,
+};
+
+extern enum vmx_l1d_flush_state l1tf_vmx_mitigation;
+
 #endif

arch/x86/kernel/cpu/bugs.c

@@ -22,6 +22,7 @@
 #include <asm/processor-flags.h>
 #include <asm/fpu/internal.h>
 #include <asm/msr.h>
+#include <asm/vmx.h>
 #include <asm/paravirt.h>
 #include <asm/alternative.h>
 #include <asm/pgtable.h>
@@ -685,6 +686,12 @@ void x86_spec_ctrl_setup_ap(void)
 
 #undef pr_fmt
 #define pr_fmt(fmt)	"L1TF: " fmt
+
+#if IS_ENABLED(CONFIG_KVM_INTEL)
+enum vmx_l1d_flush_state l1tf_vmx_mitigation __ro_after_init = VMENTER_L1D_FLUSH_AUTO;
+EXPORT_SYMBOL_GPL(l1tf_vmx_mitigation);
+#endif
+
 static void __init l1tf_select_mitigation(void)
 {
 	u64 half_pa;
@@ -714,6 +721,32 @@ static void __init l1tf_select_mitigation(void)
 
 #ifdef CONFIG_SYSFS
 
+#define L1TF_DEFAULT_MSG "Mitigation: PTE Inversion"
+
+#if IS_ENABLED(CONFIG_KVM_INTEL)
+static const char *l1tf_vmx_states[] = {
+	[VMENTER_L1D_FLUSH_AUTO]	= "auto",
+	[VMENTER_L1D_FLUSH_NEVER]	= "vulnerable",
+	[VMENTER_L1D_FLUSH_COND]	= "conditional cache flushes",
+	[VMENTER_L1D_FLUSH_ALWAYS]	= "cache flushes",
+};
+
+static ssize_t l1tf_show_state(char *buf)
+{
+	if (l1tf_vmx_mitigation == VMENTER_L1D_FLUSH_AUTO)
+		return sprintf(buf, "%s\n", L1TF_DEFAULT_MSG);
+
+	return sprintf(buf, "%s; VMX: SMT %s, L1D %s\n", L1TF_DEFAULT_MSG,
+		       cpu_smt_control == CPU_SMT_ENABLED ? "vulnerable" : "disabled",
+		       l1tf_vmx_states[l1tf_vmx_mitigation]);
+}
+#else
+static ssize_t l1tf_show_state(char *buf)
+{
+	return sprintf(buf, "%s\n", L1TF_DEFAULT_MSG);
+}
+#endif
+
 static ssize_t cpu_show_common(struct device *dev, struct device_attribute *attr,
 			       char *buf, unsigned int bug)
 {
@@ -741,9 +774,8 @@ static ssize_t cpu_show_common(struct device *dev, struct device_attribute *attr
 
 	case X86_BUG_L1TF:
 		if (boot_cpu_has(X86_FEATURE_L1TF_PTEINV))
-			return sprintf(buf, "Mitigation: Page Table Inversion\n");
+			return l1tf_show_state(buf);
 		break;
-
 	default:
 		break;
 	}

arch/x86/kvm/vmx.c

@@ -178,19 +178,13 @@ extern const ulong vmx_return;
 
 static DEFINE_STATIC_KEY_FALSE(vmx_l1d_should_flush);
 
-/* These MUST be in sync with vmentry_l1d_param order. */
-enum vmx_l1d_flush_state {
-	VMENTER_L1D_FLUSH_NEVER,
-	VMENTER_L1D_FLUSH_COND,
-	VMENTER_L1D_FLUSH_ALWAYS,
-};
-
 static enum vmx_l1d_flush_state __read_mostly vmentry_l1d_flush = VMENTER_L1D_FLUSH_COND;
 
 static const struct {
 	const char *option;
 	enum vmx_l1d_flush_state cmd;
 } vmentry_l1d_param[] = {
+	{"auto",	VMENTER_L1D_FLUSH_AUTO},
 	{"never",	VMENTER_L1D_FLUSH_NEVER},
 	{"cond",	VMENTER_L1D_FLUSH_COND},
 	{"always",	VMENTER_L1D_FLUSH_ALWAYS},
@@ -11204,8 +11198,12 @@ static int __init vmx_setup_l1d_flush(void)
 {
 	struct page *page;
 
+	if (!boot_cpu_has_bug(X86_BUG_L1TF))
+		return 0;
+
+	l1tf_vmx_mitigation = vmentry_l1d_flush;
+
 	if (vmentry_l1d_flush == VMENTER_L1D_FLUSH_NEVER ||
-	    !boot_cpu_has_bug(X86_BUG_L1TF) ||
 	    vmx_l1d_use_msr_save_list())
 		return 0;
 
@@ -11220,12 +11218,14 @@ static int __init vmx_setup_l1d_flush(void)
 	return 0;
 }
 
-static void vmx_free_l1d_flush_pages(void)
+static void vmx_cleanup_l1d_flush(void)
 {
 	if (vmx_l1d_flush_pages) {
 		free_pages((unsigned long)vmx_l1d_flush_pages, L1D_CACHE_ORDER);
 		vmx_l1d_flush_pages = NULL;
 	}
+	/* Restore state so sysfs ignores VMX */
+	l1tf_vmx_mitigation = VMENTER_L1D_FLUSH_AUTO;
 }
 
 static int __init vmx_init(void)
@@ -11239,7 +11239,7 @@ static int __init vmx_init(void)
 	r = kvm_init(&vmx_x86_ops, sizeof(struct vcpu_vmx),
 		     __alignof__(struct vcpu_vmx), THIS_MODULE);
 	if (r) {
-		vmx_free_l1d_flush_pages();
+		vmx_cleanup_l1d_flush();
 		return r;
 	}
 
@@ -11260,7 +11260,7 @@ static void __exit vmx_exit(void)
 
 	kvm_exit();
 
-	vmx_free_l1d_flush_pages();
+	vmx_cleanup_l1d_flush();
 }
 
 module_init(vmx_init)