kvm, vmx: Fix lazy FPU on nested guest

If a nested guest does a NM fault but its CR0 doesn't contain the TS
flag (because it was already cleared by the guest with L1 aid) then we
have to activate FPU ourselves in L0 and then continue to L2. If TS flag
is set then we fallback on the previous behavior, forward the fault to
L1 if it asked for.

Signed-off-by: Anthoine Bourgeois <bourgeois@bertin.fr>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index e293a62a11d6..b2fe1c252f35 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -6643,6 +6643,9 @@ static bool nested_vmx_exit_handled(struct kvm_vcpu *vcpu)
                         return 0;
                 else if (is_page_fault(intr_info))
                         return enable_ept;
+                else if (is_no_device(intr_info) &&
+                         !(nested_read_cr0(vmcs12) & X86_CR0_TS))
+                        return 0;
                 return vmcs12->exception_bitmap &
                                 (1u << (intr_info & INTR_INFO_VECTOR_MASK));
         case EXIT_REASON_EXTERNAL_INTERRUPT: