linux-kernel - [PATCH] KVM: VMX: Set VMENTER_L1D_FLUSH_NOT_REQUIRED if !X86_BUG

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Message-Id: <20190826193023.23293-1-longman@redhat.com>
Date:   Mon, 26 Aug 2019 15:30:23 -0400
From:   Waiman Long <longman@...hat.com>
To:     Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>
Cc:     x86@...nel.org, kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Waiman Long <longman@...hat.com>
Subject: [PATCH] KVM: VMX: Set VMENTER_L1D_FLUSH_NOT_REQUIRED if !X86_BUG_L1TF

The l1tf_vmx_mitigation is only set to VMENTER_L1D_FLUSH_NOT_REQUIRED
when the ARCH_CAPABILITIES MSR indicates that L1D flush is not required.
However, if the CPU is not affected by L1TF, l1tf_vmx_mitigation will
still be set to VMENTER_L1D_FLUSH_AUTO. This is certainly not the best
option for a !X86_BUG_L1TF CPU.

So force l1tf_vmx_mitigation to VMENTER_L1D_FLUSH_NOT_REQUIRED to make it
more explicit in case users are checking the vmentry_l1d_flush parameter.

Signed-off-by: Waiman Long <longman@...hat.com>
---
 arch/x86/kvm/vmx/vmx.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 42ed3faa6af8..a00ce3d6bbfd 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -7896,6 +7896,8 @@ static int __init vmx_init(void)
 			vmx_exit();
 			return r;
 		}
+	} else {
+		l1tf_vmx_mitigation = VMENTER_L1D_FLUSH_NOT_REQUIRED;
 	}

 #ifdef CONFIG_KEXEC_CORE
-- 
2.18.1