From 3a8e7f6993c8240f6cc8564ff06702512b3b18bb Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Wed, 27 Feb 2019 12:48:14 +0100 Subject: [PATCH] x86/kvm/vmx: Add MDS protection when L1D Flush is not active commit 650b68a0622f933444a6d66936abb3103029413b upstream. CPUs which are affected by L1TF and MDS mitigate MDS with the L1D Flush on VMENTER when updated microcode is installed. If a CPU is not affected by L1TF or if the L1D Flush is not in use, then MDS mitigation needs to be invoked explicitly. For these cases, follow the host mitigation state and invoke the MDS mitigation before VMENTER. Signed-off-by: Thomas Gleixner Reviewed-by: Greg Kroah-Hartman Reviewed-by: Frederic Weisbecker Reviewed-by: Borislav Petkov Reviewed-by: Jon Masters Tested-by: Jon Masters Signed-off-by: Ben Hutchings Signed-off-by: Greg Kroah-Hartman --- arch/x86/kernel/cpu/bugs.c | 1 + arch/x86/kvm/vmx.c | 3 +++ 2 files changed, 4 insertions(+) diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index 4dc04dc..8412998 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -61,6 +61,7 @@ DEFINE_STATIC_KEY_FALSE(switch_mm_always_ibpb); /* Control MDS CPU buffer clear before returning to user space */ DEFINE_STATIC_KEY_FALSE(mds_user_clear); +EXPORT_SYMBOL_GPL(mds_user_clear); void __init check_bugs(void) { diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index 75466d9..5e44c25 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -9206,8 +9206,11 @@ static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu) vmx->__launched = vmx->loaded_vmcs->launched; + /* L1D Flush includes CPU buffer clear to mitigate MDS */ if (static_branch_unlikely(&vmx_l1d_should_flush)) vmx_l1d_flush(vcpu); + else if (static_branch_unlikely(&mds_user_clear)) + mds_clear_cpu_buffers(); asm( /* Store host registers */ -- 2.7.4