[PATCH] KVM: x86: Mark expected switch fall-throughs

[PATCH] KVM: x86: Mark expected switch fall-throughs

[Gustavo A. R. Silva]

In preparation to enabling -Wimplicit-fallthrough, mark switch
cases where we are expecting to fall through.

This patch fixes the following warnings:

arch/x86/kvm/lapic.c:1037:27: warning: this statement may fall through [-Wimplicit-fallthrough=]
arch/x86/kvm/lapic.c:1876:3: warning: this statement may fall through [-Wimplicit-fallthrough=]
arch/x86/kvm/hyperv.c:1637:6: warning: this statement may fall through [-Wimplicit-fallthrough=]
arch/x86/kvm/svm.c:4396:6: warning: this statement may fall through [-Wimplicit-fallthrough=]
arch/x86/kvm/mmu.c:4372:36: warning: this statement may fall through [-Wimplicit-fallthrough=]
arch/x86/kvm/x86.c:3835:6: warning: this statement may fall through [-Wimplicit-fallthrough=]
arch/x86/kvm/x86.c:7938:23: warning: this statement may fall through [-Wimplicit-fallthrough=]
arch/x86/kvm/vmx/vmx.c:2015:6: warning: this statement may fall through [-Wimplicit-fallthrough=]
arch/x86/kvm/vmx/vmx.c:1773:6: warning: this statement may fall through [-Wimplicit-fallthrough=]

Warning level 3 was used: -Wimplicit-fallthrough=3

This patch is part of the ongoing efforts to enabling -Wimplicit-fallthrough.

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
---
 arch/x86/kvm/hyperv.c  | 2 +-
 arch/x86/kvm/lapic.c   | 2 ++
 arch/x86/kvm/mmu.c     | 1 +
 arch/x86/kvm/svm.c     | 2 +-
 arch/x86/kvm/vmx/vmx.c | 4 ++--
 arch/x86/kvm/x86.c     | 3 +++
 6 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index c90a5352d158..9c67efec613d 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -1636,7 +1636,7 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
 		ret = kvm_hvcall_signal_event(vcpu, fast, ingpa);
 		if (ret != HV_STATUS_INVALID_PORT_ID)
 			break;
-		/* maybe userspace knows this conn_id: fall through */
+		/* fall through - maybe userspace knows this conn_id. */
 	case HVCALL_POST_MESSAGE:
 		/* don't bother userspace if it has no way to handle it */
 		if (unlikely(rep || !vcpu_to_synic(vcpu)->active)) {
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 9f089e2e09d0..4b6c2da7265c 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -1035,6 +1035,7 @@ static int __apic_accept_irq(struct kvm_lapic *apic, int delivery_mode,
 	switch (delivery_mode) {
 	case APIC_DM_LOWEST:
 		vcpu->arch.apic_arb_prio++;
+		/* fall through */
 	case APIC_DM_FIXED:
 		if (unlikely(trig_mode && !level))
 			break;
@@ -1874,6 +1875,7 @@ int kvm_lapic_reg_write(struct kvm_lapic *apic, u32 reg, u32 val)
 
 	case APIC_LVT0:
 		apic_manage_nmi_watchdog(apic, val);
+		/* fall through */
 	case APIC_LVTTHMR:
 	case APIC_LVTPC:
 	case APIC_LVT1:
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index ce770b446238..da9c42349b1f 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -4371,6 +4371,7 @@ __reset_rsvds_bits_mask(struct kvm_vcpu *vcpu,
 			rsvd_bits(maxphyaddr, 51);
 		rsvd_check->rsvd_bits_mask[1][4] =
 			rsvd_check->rsvd_bits_mask[0][4];
+		/* fall through */
 	case PT64_ROOT_4LEVEL:
 		rsvd_check->rsvd_bits_mask[0][3] = exb_bit_rsvd |
 			nonleaf_bit8_rsvd | rsvd_bits(7, 7) |
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index a157ca5b6869..36bda524c883 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -4395,7 +4395,7 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr)
 	case MSR_IA32_APICBASE:
 		if (kvm_vcpu_apicv_active(vcpu))
 			avic_update_vapic_bar(to_svm(vcpu), data);
-		/* Follow through */
+		/* Fall through */
 	default:
 		return kvm_set_msr_common(vcpu, msr);
 	}
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index f6915f10e584..1de38062026e 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -1773,7 +1773,7 @@ static int vmx_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 		if (!msr_info->host_initiated &&
 		    !guest_cpuid_has(vcpu, X86_FEATURE_RDTSCP))
 			return 1;
-		/* Otherwise falls through */
+		/* Else, falls through */
 	default:
 		msr = find_msr_entry(vmx, msr_info->index);
 		if (msr) {
@@ -2014,7 +2014,7 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 		/* Check reserved bit, higher 32 bits should be zero */
 		if ((data >> 32) != 0)
 			return 1;
-		/* Otherwise falls through */
+		/* Else, falls through */
 	default:
 		msr = find_msr_entry(vmx, msr_index);
 		if (msr) {
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 02c8e095a239..6d514619afd3 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3834,6 +3834,8 @@ static int kvm_vcpu_ioctl_enable_cap(struct kvm_vcpu *vcpu,
 	case KVM_CAP_HYPERV_SYNIC2:
 		if (cap->args[0])
 			return -EINVAL;
+		/* fall through */
+
 	case KVM_CAP_HYPERV_SYNIC:
 		if (!irqchip_in_kernel(vcpu->kvm))
 			return -EINVAL;
@@ -7937,6 +7939,7 @@ static inline int vcpu_block(struct kvm *kvm, struct kvm_vcpu *vcpu)
 		vcpu->arch.pv.pv_unhalted = false;
 		vcpu->arch.mp_state =
 			KVM_MP_STATE_RUNNABLE;
+		/* fall through */
 	case KVM_MP_STATE_RUNNABLE:
 		vcpu->arch.apf.halted = false;
 		break;
-- 
2.20.1

Re: [PATCH] KVM: x86: Mark expected switch fall-throughs

[Paolo Bonzini]

On 25/01/19 19:23, Gustavo A. R. Silva wrote:
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index f6915f10e584..1de38062026e 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -1773,7 +1773,7 @@ static int vmx_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
>  		if (!msr_info->host_initiated &&
>  		    !guest_cpuid_has(vcpu, X86_FEATURE_RDTSCP))
>  			return 1;
> -		/* Otherwise falls through */
> +		/* Else, falls through */
>  	default:
>  		msr = find_msr_entry(vmx, msr_info->index);
>  		if (msr) {

I would say this is a compiler QoI issue and in general there were other
cases like this one where the comments in the KVM source are reasonable,
but I guess it's okay.  Patch queued.

Paolo