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Commit 3f5ad8be authored by Paolo Bonzini's avatar Paolo Bonzini
Browse files

KVM: hyperv: fix locking of struct kvm_hv fields 



Introduce a new mutex to avoid an AB-BA deadlock between kvm->lock and
vcpu->mutex.  Protect accesses in kvm_hv_setup_tsc_page too, as suggested
by Roman.

Reported-by: default avatarDmitry Vyukov <dvyukov@google.com>
Reviewed-by: default avatarRoman Kagan <rkagan@virtuozzo.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 83781d18

Documentation/virtual/kvm/locking.txt

+6 −2
Original line number Diff line number Diff line
@@ -13,8 +13,12 @@ The acquisition orders for mutexes are as follows: 
- kvm->slots_lock is taken outside kvm->irq_lock, though acquiring

  them together is quite rare.



For spinlocks, kvm_lock is taken outside kvm->mmu_lock.  Everything

else is a leaf: no other lock is taken inside the critical sections.

On x86, vcpu->mutex is taken outside kvm->arch.hyperv.hv_lock.



For spinlocks, kvm_lock is taken outside kvm->mmu_lock.



Everything else is a leaf: no other lock is taken inside the critical

sections.



2: Exception

------------

arch/x86/include/asm/kvm_host.h

+1 −0
Original line number Diff line number Diff line
@@ -704,6 +704,7 @@ struct kvm_apic_map { 


/* Hyper-V emulation context */

struct kvm_hv {

	struct mutex hv_lock;

	u64 hv_guest_os_id;

	u64 hv_hypercall;

	u64 hv_tsc_page;

arch/x86/kvm/hyperv.c

+15 −9
Original line number Diff line number Diff line
@@ -852,6 +852,10 @@ void kvm_hv_setup_tsc_page(struct kvm *kvm, 
	if (!(hv->hv_tsc_page & HV_X64_MSR_TSC_REFERENCE_ENABLE))

		return;



	mutex_lock(&kvm->arch.hyperv.hv_lock);

	if (!(hv->hv_tsc_page & HV_X64_MSR_TSC_REFERENCE_ENABLE))

		goto out_unlock;



	gfn = hv->hv_tsc_page >> HV_X64_MSR_TSC_REFERENCE_ADDRESS_SHIFT;

	/*

	 * Because the TSC parameters only vary when there is a
@@ -859,7 +863,7 @@ void kvm_hv_setup_tsc_page(struct kvm *kvm, 
	 */

	if (unlikely(kvm_read_guest(kvm, gfn_to_gpa(gfn),

				    &tsc_seq, sizeof(tsc_seq))))

		return;

		goto out_unlock;



	/*

	 * While we're computing and writing the parameters, force the
@@ -868,15 +872,15 @@ void kvm_hv_setup_tsc_page(struct kvm *kvm, 
	hv->tsc_ref.tsc_sequence = 0;

	if (kvm_write_guest(kvm, gfn_to_gpa(gfn),

			    &hv->tsc_ref, sizeof(hv->tsc_ref.tsc_sequence)))

		return;

		goto out_unlock;



	if (!compute_tsc_page_parameters(hv_clock, &hv->tsc_ref))

		return;

		goto out_unlock;



	/* Ensure sequence is zero before writing the rest of the struct.  */

	smp_wmb();

	if (kvm_write_guest(kvm, gfn_to_gpa(gfn), &hv->tsc_ref, sizeof(hv->tsc_ref)))

		return;

		goto out_unlock;



	/*

	 * Now switch to the TSC page mechanism by writing the sequence.
@@ -891,6 +895,8 @@ void kvm_hv_setup_tsc_page(struct kvm *kvm, 
	hv->tsc_ref.tsc_sequence = tsc_seq;

	kvm_write_guest(kvm, gfn_to_gpa(gfn),

			&hv->tsc_ref, sizeof(hv->tsc_ref.tsc_sequence));

out_unlock:

	mutex_unlock(&kvm->arch.hyperv.hv_lock);

}



static int kvm_hv_set_msr_pw(struct kvm_vcpu *vcpu, u32 msr, u64 data,
@@ -1142,9 +1148,9 @@ int kvm_hv_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 data, bool host) 
	if (kvm_hv_msr_partition_wide(msr)) {

		int r;



		mutex_lock(&vcpu->kvm->lock);

		mutex_lock(&vcpu->kvm->arch.hyperv.hv_lock);

		r = kvm_hv_set_msr_pw(vcpu, msr, data, host);

		mutex_unlock(&vcpu->kvm->lock);

		mutex_unlock(&vcpu->kvm->arch.hyperv.hv_lock);

		return r;

	} else

		return kvm_hv_set_msr(vcpu, msr, data, host);
@@ -1155,9 +1161,9 @@ int kvm_hv_get_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata) 
	if (kvm_hv_msr_partition_wide(msr)) {

		int r;



		mutex_lock(&vcpu->kvm->lock);

		mutex_lock(&vcpu->kvm->arch.hyperv.hv_lock);

		r = kvm_hv_get_msr_pw(vcpu, msr, pdata);

		mutex_unlock(&vcpu->kvm->lock);

		mutex_unlock(&vcpu->kvm->arch.hyperv.hv_lock);

		return r;

	} else

		return kvm_hv_get_msr(vcpu, msr, pdata);
@@ -1165,7 +1171,7 @@ int kvm_hv_get_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata) 


bool kvm_hv_hypercall_enabled(struct kvm *kvm)

{

	return kvm->arch.hyperv.hv_hypercall & HV_X64_MSR_HYPERCALL_ENABLE;

	return READ_ONCE(kvm->arch.hyperv.hv_hypercall) & HV_X64_MSR_HYPERCALL_ENABLE;

}



static void kvm_hv_hypercall_set_result(struct kvm_vcpu *vcpu, u64 result)

arch/x86/kvm/x86.c

+1 −0
Original line number Diff line number Diff line
@@ -7881,6 +7881,7 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type) 


	raw_spin_lock_init(&kvm->arch.tsc_write_lock);

	mutex_init(&kvm->arch.apic_map_lock);

	mutex_init(&kvm->arch.hyperv.hv_lock);

	spin_lock_init(&kvm->arch.pvclock_gtod_sync_lock);



	kvm->arch.kvmclock_offset = -ktime_get_boot_ns();