linux-kernel - [PATCH 4.9 083/107] x86/KVM/VMX: Dont set l1tf_flush_l1d to true from vmx_l1d

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Date:   Tue, 14 Aug 2018 19:17:46 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Nicolai Stange <nstange@...e.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        David Woodhouse <dwmw@...zon.co.uk>
Subject: [PATCH 4.9 083/107] x86/KVM/VMX: Dont set l1tf_flush_l1d to true from vmx_l1d_flush()

4.9-stable review patch.  If anyone has any objections, please let me know.

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

From: Nicolai Stange <nstange@...e.de>

commit 379fd0c7e6a391e5565336a646f19f218fb98c6c upstream

vmx_l1d_flush() gets invoked only if l1tf_flush_l1d is true. There's no
point in setting l1tf_flush_l1d to true from there again.

Signed-off-by: Nicolai Stange <nstange@...e.de>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: David Woodhouse <dwmw@...zon.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 arch/x86/kvm/vmx.c |   14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -8665,15 +8665,15 @@ static void vmx_l1d_flush(struct kvm_vcp
 	/*
 	 * This code is only executed when the the flush mode is 'cond' or
 	 * 'always'
-	 *
-	 * If 'flush always', keep the flush bit set, otherwise clear
-	 * it. The flush bit gets set again either from vcpu_run() or from
-	 * one of the unsafe VMEXIT handlers.
 	 */
-	if (static_branch_unlikely(&vmx_l1d_flush_always))
-		vcpu->arch.l1tf_flush_l1d = true;
-	else
+	if (!static_branch_unlikely(&vmx_l1d_flush_always)) {
+		/*
+		 * Clear the flush bit, it gets set again either from
+		 * vcpu_run() or from one of the unsafe VMEXIT
+		 * handlers.
+		 */
 		vcpu->arch.l1tf_flush_l1d = false;
+	}
 
 	vcpu->stat.l1d_flush++;