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Subject[PATCH v2] KVM: VMX: Set VMENTER_L1D_FLUSH_NOT_REQUIRED if !X86_BUG_L1TF
Date
From: Waiman Long <longman@redhat.com>

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>
---
arch/x86/kvm/vmx/vmx.c | 15 +++++++++------
1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index d4575ffb3cec..e7970a2e8eae 100644
--- 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
--
1.8.3.1
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