linux-kernel - [PATCH] KVM: nVMX: fixes for preemption timer migration

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Date:   Thu,  9 Jul 2020 13:15:07 -0400
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     bsd@...hat.com, Makarand Sonare <makarandsonare@...gle.com>
Subject: [PATCH] KVM: nVMX: fixes for preemption timer migration

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 <makarandsonare@...gle.com>
Fixes: 850448f35aaf ("KVM: nVMX: Fix VMX preemption timer migration")
Signed-off-by: Paolo Bonzini <pbonzini@...hat.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