[PATCH] KVM: nVMX: fixes for preemption timer migration

[Paolo Bonzini]

Commit 850448f35aaf ("KVM: nVMX: Fix VMX preemption timer migration",
2020-06-01) accidentally broke nVMX live migration from older version
by changing the userspace ABI.  Restore it and, while at it, ensure
that vmx->nested.has_preemption_timer_deadline is always initialized
according to the KVM_STATE_VMX_PREEMPTION_TIMER_DEADLINE flag.

Cc: Makarand Sonare <makarandson...@google.com>
Fixes: 850448f35aaf ("KVM: nVMX: Fix VMX preemption timer migration")
Signed-off-by: Paolo Bonzini <pbonz...@redhat.com>
---
 arch/x86/include/uapi/asm/kvm.h | 5 +++--
 arch/x86/kvm/vmx/nested.c       | 3 ++-
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/arch/x86/include/uapi/asm/kvm.h b/arch/x86/include/uapi/asm/kvm.h
index 17c5a038f42d..0780f97c1850 100644
--- a/arch/x86/include/uapi/asm/kvm.h
+++ b/arch/x86/include/uapi/asm/kvm.h
@@ -408,14 +408,15 @@ struct kvm_vmx_nested_state_data {
 };
 
 struct kvm_vmx_nested_state_hdr {
-       __u32 flags;
        __u64 vmxon_pa;
        __u64 vmcs12_pa;
-       __u64 preemption_timer_deadline;
 
        struct {
                __u16 flags;
        } smm;
+
+       __u32 flags;
+       __u64 preemption_timer_deadline;
 };
 
 struct kvm_svm_nested_state_data {
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index b26655104d4a..3fc2411edc92 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -6180,7 +6180,8 @@ static int vmx_set_nested_state(struct kvm_vcpu *vcpu,
                vmx->nested.has_preemption_timer_deadline = true;
                vmx->nested.preemption_timer_deadline =
                        kvm_state->hdr.vmx.preemption_timer_deadline;
-       }
+       } else
+               vmx->nested.has_preemption_timer_deadline = false;
 
        if (nested_vmx_check_controls(vcpu, vmcs12) ||
            nested_vmx_check_host_state(vcpu, vmcs12) ||
-- 
2.26.2