KVM: nSVM: Use the "outer" helper for writing multiplier to MSR_AMD64_TSC_RATIO

When emulating nested SVM transitions, use the outer helper for writing
the TSC multiplier for L2.  Using the inner helper only for one-off cases,
i.e. for paths where KVM is NOT emulating or modifying vCPU state, will
allow for multiple cleanups:

 - Explicitly disabling preemption only in the outer helper
 - Getting the multiplier from the vCPU field in the outer helper
 - Skipping the WRMSR in the outer helper if guest state isn't loaded

Opportunistically delete an extra newline.

No functional change intended.

Link: https://lore.kernel.org/r/20230729011608.1065019-4-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

Author: sean-jc

arch/x86/kvm/svm/nested.c

@@ -1103,7 +1103,7 @@ int nested_svm_vmexit(struct vcpu_svm *svm)
 	if (kvm_caps.has_tsc_control &&
 	    vcpu->arch.tsc_scaling_ratio != vcpu->arch.l1_tsc_scaling_ratio) {
 		vcpu->arch.tsc_scaling_ratio = vcpu->arch.l1_tsc_scaling_ratio;
-		__svm_write_tsc_multiplier(vcpu->arch.tsc_scaling_ratio);
+		svm_write_tsc_multiplier(vcpu, vcpu->arch.tsc_scaling_ratio);
 	}
 
 	svm->nested.ctl.nested_cr3 = 0;
@@ -1536,7 +1536,7 @@ void nested_svm_update_tsc_ratio_msr(struct kvm_vcpu *vcpu)
 	vcpu->arch.tsc_scaling_ratio =
 		kvm_calc_nested_tsc_multiplier(vcpu->arch.l1_tsc_scaling_ratio,
 					       svm->tsc_ratio_msr);
-	__svm_write_tsc_multiplier(vcpu->arch.tsc_scaling_ratio);
+	svm_write_tsc_multiplier(vcpu, vcpu->arch.tsc_scaling_ratio);
 }
 
 /* Inverse operation of nested_copy_vmcb_control_to_cache(). asid is copied too. */

arch/x86/kvm/svm/svm.c

@@ -567,7 +567,7 @@ static int svm_check_processor_compat(void)
 	return 0;
 }
 
-void __svm_write_tsc_multiplier(u64 multiplier)
+static void __svm_write_tsc_multiplier(u64 multiplier)
 {
 	preempt_disable();
 
@@ -1150,12 +1150,11 @@ static void svm_write_tsc_offset(struct kvm_vcpu *vcpu, u64 offset)
 	vmcb_mark_dirty(svm->vmcb, VMCB_INTERCEPTS);
 }
 
-static void svm_write_tsc_multiplier(struct kvm_vcpu *vcpu, u64 multiplier)
+void svm_write_tsc_multiplier(struct kvm_vcpu *vcpu, u64 multiplier)
 {
 	__svm_write_tsc_multiplier(multiplier);
 }
 
-
 /* Evaluate instruction intercepts that depend on guest CPUID features. */
 static void svm_recalc_instruction_intercepts(struct kvm_vcpu *vcpu,
 					      struct vcpu_svm *svm)

arch/x86/kvm/svm/svm.h

@@ -658,7 +658,7 @@ int nested_svm_check_exception(struct vcpu_svm *svm, unsigned nr,
 			       bool has_error_code, u32 error_code);
 int nested_svm_exit_special(struct vcpu_svm *svm);
 void nested_svm_update_tsc_ratio_msr(struct kvm_vcpu *vcpu);
-void __svm_write_tsc_multiplier(u64 multiplier);
+void svm_write_tsc_multiplier(struct kvm_vcpu *vcpu, u64 multiplier);
 void nested_copy_vmcb_control_to_cache(struct vcpu_svm *svm,
 				       struct vmcb_control_area *control);
 void nested_copy_vmcb_save_to_cache(struct vcpu_svm *svm,