KVM: nVMX: Drop manual clearing of segment cache on nested VMCS switch

Drop the call to vmx_segment_cache_clear() in vmx_switch_vmcs() now that
the entire register cache is reset when switching the active VMCS, e.g.
vmx_segment_cache_test_set() will reset the segment cache due to
VCPU_EXREG_SEGMENTS being unavailable.

Move vmx_segment_cache_clear() to vmx.c now that it's no longer invoked
by the nested code.
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Message-Id: <20200415203454.8296-4-sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/vmx/nested.c

@@ -308,7 +308,6 @@ static void vmx_switch_vmcs(struct kvm_vcpu *vcpu, struct loaded_vmcs *vmcs)
 	put_cpu();
 
 	vmx_register_cache_reset(vcpu);
-	vmx_segment_cache_clear(vmx);
 }
 
 /*

arch/x86/kvm/vmx/vmx.c

@@ -437,6 +437,11 @@ static const struct kvm_vmx_segment_field {
 	VMX_SEGMENT_FIELD(LDTR),
 };
 
+static inline void vmx_segment_cache_clear(struct vcpu_vmx *vmx)
+{
+	vmx->segment_cache.bitmask = 0;
+}
+
 static unsigned long host_idt_base;
 
 /*

arch/x86/kvm/vmx/vmx.h

@@ -443,11 +443,6 @@ BUILD_CONTROLS_SHADOW(pin, PIN_BASED_VM_EXEC_CONTROL)
 BUILD_CONTROLS_SHADOW(exec, CPU_BASED_VM_EXEC_CONTROL)
 BUILD_CONTROLS_SHADOW(secondary_exec, SECONDARY_VM_EXEC_CONTROL)
 
-static inline void vmx_segment_cache_clear(struct vcpu_vmx *vmx)
-{
-	vmx->segment_cache.bitmask = 0;
-}
-
 static inline void vmx_register_cache_reset(struct kvm_vcpu *vcpu)
 {
 	vcpu->arch.regs_avail = ~((1 << VCPU_REGS_RIP) | (1 << VCPU_REGS_RSP)