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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Thomas Gleixner <tglx@linutronix.de>,
        Jiri Kosina <jkosina@suse.cz>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        David Woodhouse <dwmw@amazon.co.uk>
Subject: [PATCH 4.9 071/107] x86/l1tf: Handle EPT disabled state proper
Date:   Tue, 14 Aug 2018 19:17:34 +0200
Message-Id: <20180814171525.164507724@linuxfoundation.org>
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References: <20180814171520.883143803@linuxfoundation.org>
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4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Thomas Gleixner <tglx@linutronix.de>

commit a7b9020b06ec6d7c3f3b0d4ef1a9eba12654f4f7 upstream

If Extended Page Tables (EPT) are disabled or not supported, no L1D
flushing is required. The setup function can just avoid setting up the L1D
flush for the EPT=n case.

Invoke it after the hardware setup has be done and enable_ept has the
correct state and expose the EPT disabled state in the mitigation status as
well.

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/20180713142322.612160168@linutronix.de
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 arch/x86/include/asm/vmx.h |    1 +
 arch/x86/kernel/cpu/bugs.c |    9 +++++----
 arch/x86/kvm/vmx.c         |   44 ++++++++++++++++++++++++++------------------
 3 files changed, 32 insertions(+), 22 deletions(-)

--- a/arch/x86/include/asm/vmx.h
+++ b/arch/x86/include/asm/vmx.h
@@ -504,6 +504,7 @@ enum vmx_l1d_flush_state {
 	VMENTER_L1D_FLUSH_NEVER,
 	VMENTER_L1D_FLUSH_COND,
 	VMENTER_L1D_FLUSH_ALWAYS,
+	VMENTER_L1D_FLUSH_EPT_DISABLED,
 };
 
 extern enum vmx_l1d_flush_state l1tf_vmx_mitigation;
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -675,10 +675,11 @@ static void __init l1tf_select_mitigatio
 
 #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",
+	[VMENTER_L1D_FLUSH_AUTO]		= "auto",
+	[VMENTER_L1D_FLUSH_NEVER]		= "vulnerable",
+	[VMENTER_L1D_FLUSH_COND]		= "conditional cache flushes",
+	[VMENTER_L1D_FLUSH_ALWAYS]		= "cache flushes",
+	[VMENTER_L1D_FLUSH_EPT_DISABLED]	= "EPT disabled",
 };
 
 static ssize_t l1tf_show_state(char *buf)
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -11659,6 +11659,11 @@ static int __init vmx_setup_l1d_flush(vo
 	if (!boot_cpu_has_bug(X86_BUG_L1TF))
 		return 0;
 
+	if (!enable_ept) {
+		l1tf_vmx_mitigation = VMENTER_L1D_FLUSH_EPT_DISABLED;
+		return 0;
+	}
+
 	l1tf_vmx_mitigation = vmentry_l1d_flush;
 
 	if (vmentry_l1d_flush == VMENTER_L1D_FLUSH_NEVER)
@@ -11685,18 +11690,35 @@ static void vmx_cleanup_l1d_flush(void)
 	l1tf_vmx_mitigation = VMENTER_L1D_FLUSH_AUTO;
 }
 
+
+static void vmx_exit(void)
+{
+#ifdef CONFIG_KEXEC_CORE
+	RCU_INIT_POINTER(crash_vmclear_loaded_vmcss, NULL);
+	synchronize_rcu();
+#endif
+
+	kvm_exit();
+
+	vmx_cleanup_l1d_flush();
+}
+module_exit(vmx_exit)
+
 static int __init vmx_init(void)
 {
 	int r;
 
-	r = vmx_setup_l1d_flush();
+	r = kvm_init(&vmx_x86_ops, sizeof(struct vcpu_vmx),
+		     __alignof__(struct vcpu_vmx), THIS_MODULE);
 	if (r)
 		return r;
 
-	r = kvm_init(&vmx_x86_ops, sizeof(struct vcpu_vmx),
-		     __alignof__(struct vcpu_vmx), THIS_MODULE);
+	/*
+	 * Must be called after kvm_init() so enable_ept is properly set up
+	 */
+	r = vmx_setup_l1d_flush();
 	if (r) {
-		vmx_cleanup_l1d_flush();
+		vmx_exit();
 		return r;
 	}
 
@@ -11707,18 +11729,4 @@ static int __init vmx_init(void)
 
 	return 0;
 }
-
-static void __exit vmx_exit(void)
-{
-#ifdef CONFIG_KEXEC_CORE
-	RCU_INIT_POINTER(crash_vmclear_loaded_vmcss, NULL);
-	synchronize_rcu();
-#endif
-
-	kvm_exit();
-
-	vmx_cleanup_l1d_flush();
-}
-
 module_init(vmx_init)
-module_exit(vmx_exit)