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@redhat.com>
[Patch rewritten accoring to Borislav Petkov's suggestion. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index d4575ffb3cec75bcb3f1fb5330c99516d6ab1265..e7970a2e8eae918f76ce8ef3646aba0f39a27275 100644 (file)
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -209,6 +209,11 @@ static int vmx_setup_l1d_flush(enum vmx_l1d_flush_state l1tf)
        struct page *page;
        unsigned int i;
 
+       if (!boot_cpu_has_bug(X86_BUG_L1TF)) {
+               l1tf_vmx_mitigation = VMENTER_L1D_FLUSH_NOT_REQUIRED;
+               return 0;
+       }
+
        if (!enable_ept) {
                l1tf_vmx_mitigation = VMENTER_L1D_FLUSH_EPT_DISABLED;
                return 0;
@@ -7995,12 +8000,10 @@ static int __init vmx_init(void)
         * contain 'auto' which will be turned into the default 'cond'
         * mitigation mode.
         */
-       if (boot_cpu_has(X86_BUG_L1TF)) {
-               r = vmx_setup_l1d_flush(vmentry_l1d_flush_param);
-               if (r) {
-                       vmx_exit();
-                       return r;
-               }
+       r = vmx_setup_l1d_flush(vmentry_l1d_flush_param);
+       if (r) {
+               vmx_exit();
+               return r;
        }
 
 #ifdef CONFIG_KEXEC_CORE