[PATCH v4 10/11] KVM: x86/hyperv: Assert vCPU's mutex is held in to_hv_vcpu()

[Sean Christopherson <seanjc@google.com>]

Assert that either vcpu->mutex is held or the VM is otherwise unreachable
when using the normal vCPU => HyperV accessor to help detect improper
cross-task usage of the HyperV structure.  When accessing the structure
without holding the vCPU's mutex, e.g. to send interrupts or to queue TLB
flushes, KVM needs to use the more paranoid to_hv_vcpu_safe() to guarantee
that it can't see a half-baked structure.

To avoid false positives, open code accesses to vcpu->arch.hyperv in the
Synthetic Timer callbacks (can be reached if and only if HyperV state is
fully initialized).

Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 arch/x86/kvm/hyperv.c | 6 ++----
 arch/x86/kvm/hyperv.h | 2 ++
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index 888526ce4dab..f765c3bb9b1f 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -599,8 +599,7 @@ static void stimer_mark_pending(struct kvm_vcpu_hv_stimer *stimer,
 {
 	struct kvm_vcpu *vcpu = hv_stimer_to_vcpu(stimer);
 
-	set_bit(stimer->index,
-		to_hv_vcpu(vcpu)->stimer_pending_bitmap);
+	set_bit(stimer->index, vcpu->arch.hyperv->stimer_pending_bitmap);
 	kvm_make_request(KVM_REQ_HV_STIMER, vcpu);
 	if (vcpu_kick)
 		kvm_vcpu_kick(vcpu);
@@ -614,8 +613,7 @@ static void stimer_cleanup(struct kvm_vcpu_hv_stimer *stimer)
 				    stimer->index);
 
 	hrtimer_cancel(&stimer->timer);
-	clear_bit(stimer->index,
-		  to_hv_vcpu(vcpu)->stimer_pending_bitmap);
+	clear_bit(stimer->index, vcpu->arch.hyperv->stimer_pending_bitmap);
 	stimer->msg_pending = false;
 	stimer->exp_time = 0;
 }
diff --git a/arch/x86/kvm/hyperv.h b/arch/x86/kvm/hyperv.h
index ea9c81d76dd3..37a0bcf03e28 100644
--- a/arch/x86/kvm/hyperv.h
+++ b/arch/x86/kvm/hyperv.h
@@ -76,6 +76,8 @@ static inline struct kvm_vcpu_hv *to_hv_vcpu_safe(struct kvm_vcpu *vcpu)
 
 static inline struct kvm_vcpu_hv *to_hv_vcpu(struct kvm_vcpu *vcpu)
 {
+	kvm_lockdep_assert_vcpu_is_locked_or_unreachable(vcpu);
+
 	return vcpu->arch.hyperv;
 }
 
-- 
2.55.0.rc0.799.gd6f94ed593-goog