[PATCH 2/5] KVM: x86: mark NULL-able kvm_x86_ops

[Paolo Bonzini]

The original use of KVM_X86_OP_NULL, which was to mark calls
that do not follow a specific naming convention, is not in use
anymore.  Repurpose it to identify calls that are invoked within
conditionals or with static_call_cond.  Those that are _not_,
i.e. those that are defined with KVM_X86_OP, must be defined by
both vendor modules or some kind of NULL pointer dereference
is bound to happen at runtime.

In the case of apicv_post_status_restore, rather than changing
the kvm-x86-ops.h declaration, I decided to use static_call_cond;
there's no absolute requirement for vendor modules to support
APIC virtualization.

Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
 arch/x86/include/asm/kvm-x86-ops.h | 30 ++++++++++++++----------------
 arch/x86/kvm/lapic.c               |  4 ++--
 2 files changed, 16 insertions(+), 18 deletions(-)

diff --git a/arch/x86/include/asm/kvm-x86-ops.h b/arch/x86/include/asm/kvm-x86-ops.h
index 9e37dc3d8863..a842f10f5778 100644
--- a/arch/x86/include/asm/kvm-x86-ops.h
+++ b/arch/x86/include/asm/kvm-x86-ops.h
@@ -6,16 +6,14 @@ BUILD_BUG_ON(1)
 /*
  * KVM_X86_OP() and KVM_X86_OP_NULL() are used to help generate
  * "static_call()"s. They are also intended for use when defining
- * the vmx/svm kvm_x86_ops. KVM_X86_OP() can be used for those
- * functions that follow the [svm|vmx]_func_name convention.
- * KVM_X86_OP_NULL() can leave a NULL definition for the
- * case where there is no definition or a function name that
- * doesn't match the typical naming convention is supplied.
+ * the vmx/svm kvm_x86_ops. KVM_X86_OP_NULL() can be used for those
+ * functions that can have a NULL definition, for example if
+ * "static_call_cond()" will be used at the call sites.
  */
-KVM_X86_OP_NULL(hardware_enable)
-KVM_X86_OP_NULL(hardware_disable)
-KVM_X86_OP_NULL(hardware_unsetup)
-KVM_X86_OP_NULL(cpu_has_accelerated_tpr)
+KVM_X86_OP(hardware_enable)
+KVM_X86_OP(hardware_disable)
+KVM_X86_OP(hardware_unsetup)
+KVM_X86_OP(cpu_has_accelerated_tpr)
 KVM_X86_OP(has_emulated_msr)
 KVM_X86_OP(vcpu_after_set_cpuid)
 KVM_X86_OP(vm_init)
@@ -33,7 +31,7 @@ KVM_X86_OP(get_segment_base)
 KVM_X86_OP(get_segment)
 KVM_X86_OP(get_cpl)
 KVM_X86_OP(set_segment)
-KVM_X86_OP_NULL(get_cs_db_l_bits)
+KVM_X86_OP(get_cs_db_l_bits)
 KVM_X86_OP(set_cr0)
 KVM_X86_OP_NULL(post_set_cr3)
 KVM_X86_OP(is_valid_cr4)
@@ -57,8 +55,8 @@ KVM_X86_OP(flush_tlb_gva)
 KVM_X86_OP(flush_tlb_guest)
 KVM_X86_OP(vcpu_pre_run)
 KVM_X86_OP(vcpu_run)
-KVM_X86_OP_NULL(handle_exit)
-KVM_X86_OP_NULL(skip_emulated_instruction)
+KVM_X86_OP(handle_exit)
+KVM_X86_OP(skip_emulated_instruction)
 KVM_X86_OP_NULL(update_emulated_instruction)
 KVM_X86_OP(set_interrupt_shadow)
 KVM_X86_OP(get_interrupt_shadow)
@@ -73,7 +71,7 @@ KVM_X86_OP(get_nmi_mask)
 KVM_X86_OP(set_nmi_mask)
 KVM_X86_OP(enable_nmi_window)
 KVM_X86_OP(enable_irq_window)
-KVM_X86_OP(update_cr8_intercept)
+KVM_X86_OP_NULL(update_cr8_intercept)
 KVM_X86_OP(check_apicv_inhibit_reasons)
 KVM_X86_OP(refresh_apicv_exec_ctrl)
 KVM_X86_OP(hwapic_irr_update)
@@ -88,7 +86,7 @@ KVM_X86_OP(set_tss_addr)
 KVM_X86_OP(set_identity_map_addr)
 KVM_X86_OP(get_mt_mask)
 KVM_X86_OP(load_mmu_pgd)
-KVM_X86_OP_NULL(has_wbinvd_exit)
+KVM_X86_OP(has_wbinvd_exit)
 KVM_X86_OP(get_l2_tsc_offset)
 KVM_X86_OP(get_l2_tsc_multiplier)
 KVM_X86_OP(write_tsc_offset)
@@ -96,7 +94,7 @@ KVM_X86_OP(write_tsc_multiplier)
 KVM_X86_OP(get_exit_info)
 KVM_X86_OP(check_intercept)
 KVM_X86_OP(handle_exit_irqoff)
-KVM_X86_OP_NULL(request_immediate_exit)
+KVM_X86_OP(request_immediate_exit)
 KVM_X86_OP(sched_in)
 KVM_X86_OP_NULL(update_cpu_dirty_logging)
 KVM_X86_OP_NULL(vcpu_blocking)
@@ -123,7 +121,7 @@ KVM_X86_OP(apic_init_signal_blocked)
 KVM_X86_OP_NULL(enable_direct_tlbflush)
 KVM_X86_OP_NULL(migrate_timers)
 KVM_X86_OP(msr_filter_changed)
-KVM_X86_OP_NULL(complete_emulated_msr)
+KVM_X86_OP(complete_emulated_msr)
 KVM_X86_OP(vcpu_deliver_sipi_vector)
 
 #undef KVM_X86_OP
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 0da7d0960fcb..09bbb6a01c1d 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -2369,7 +2369,7 @@ void kvm_lapic_reset(struct kvm_vcpu *vcpu, bool init_event)
 	vcpu->arch.pv_eoi.msr_val = 0;
 	apic_update_ppr(apic);
 	if (vcpu->arch.apicv_active) {
-		static_call(kvm_x86_apicv_post_state_restore)(vcpu);
+		static_call_cond(kvm_x86_apicv_post_state_restore)(vcpu);
 		static_call(kvm_x86_hwapic_irr_update)(vcpu, -1);
 		static_call(kvm_x86_hwapic_isr_update)(vcpu, -1);
 	}
@@ -2634,7 +2634,7 @@ int kvm_apic_set_state(struct kvm_vcpu *vcpu, struct kvm_lapic_state *s)
 	kvm_apic_update_apicv(vcpu);
 	apic->highest_isr_cache = -1;
 	if (vcpu->arch.apicv_active) {
-		static_call(kvm_x86_apicv_post_state_restore)(vcpu);
+		static_call_cond(kvm_x86_apicv_post_state_restore)(vcpu);
 		static_call(kvm_x86_hwapic_irr_update)(vcpu,
 				apic_find_highest_irr(apic));
 		static_call(kvm_x86_hwapic_isr_update)(vcpu,
-- 
2.31.1