KVM: x86: Add kvm_emulate_{rd,wr}msr() to consolidate VXM/SVM code

Move RDMSR and WRMSR emulation into common x86 code to consolidate
nearly identical SVM and VMX code.

Note, consolidating RDMSR introduces an extra indirect call, i.e.
retpoline, due to reaching {svm,vmx}_get_msr() via kvm_x86_ops, but a
guest kernel likely has bigger problems if increasing the latency of
RDMSR VM-Exits by ~70 cycles has a measurable impact on overall VM
performance.  E.g. the only recurring RDMSR VM-Exits (after booting) on
my system running Linux 5.2 in the guest are for MSR_IA32_TSC_ADJUST via
arch_cpu_idle_enter().

No functional change intended.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 2 insertions, 27 deletions

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index a08a8f111c0a..890b1bffcf7c 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -4220,22 +4220,7 @@ static int svm_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 
 static int rdmsr_interception(struct vcpu_svm *svm)
 {
-	u32 ecx = kvm_rcx_read(&svm->vcpu);
-	struct msr_data msr_info;
-
-	msr_info.index = ecx;
-	msr_info.host_initiated = false;
-	if (svm_get_msr(&svm->vcpu, &msr_info)) {
-		trace_kvm_msr_read_ex(ecx);
-		kvm_inject_gp(&svm->vcpu, 0);
-		return 1;
-	} else {
-		trace_kvm_msr_read(ecx, msr_info.data);
-
-		kvm_rax_write(&svm->vcpu, msr_info.data & 0xffffffff);
-		kvm_rdx_write(&svm->vcpu, msr_info.data >> 32);
-		return kvm_skip_emulated_instruction(&svm->vcpu);
-	}
+	return kvm_emulate_rdmsr(&svm->vcpu);
 }
 
 static int svm_set_vm_cr(struct kvm_vcpu *vcpu, u64 data)
@@ -4425,17 +4410,7 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr)
 
 static int wrmsr_interception(struct vcpu_svm *svm)
 {
-	u32 ecx = kvm_rcx_read(&svm->vcpu);
-	u64 data = kvm_read_edx_eax(&svm->vcpu);
-
-	if (kvm_set_msr(&svm->vcpu, ecx, data)) {
-		trace_kvm_msr_write_ex(ecx, data);
-		kvm_inject_gp(&svm->vcpu, 0);
-		return 1;
-	} else {
-		trace_kvm_msr_write(ecx, data);
-		return kvm_skip_emulated_instruction(&svm->vcpu);
-	}
+	return kvm_emulate_wrmsr(&svm->vcpu);
 }
 
 static int msr_interception(struct vcpu_svm *svm)