[2/2] KVM: x86: Add kvm_emulate_{rd,wr}msr() to consolidate VXM/SVM code
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Message ID 20190905212255.26549-3-sean.j.christopherson@intel.com
State New
Headers show
Series
  • KVM: x86: Refactor MSR related helpers
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Commit Message

Sean Christopherson Sept. 5, 2019, 9:22 p.m. UTC
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>
---
 arch/x86/include/asm/kvm_host.h |  2 ++
 arch/x86/kvm/svm.c              | 29 ++-------------------------
 arch/x86/kvm/vmx/vmx.c          | 29 ++-------------------------
 arch/x86/kvm/x86.c              | 35 +++++++++++++++++++++++++++++++++
 4 files changed, 41 insertions(+), 54 deletions(-)

Patch
diff mbox series

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 649d80b5cd6f..003c1cc8e28b 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1328,6 +1328,8 @@  void kvm_enable_efer_bits(u64);
 bool kvm_valid_efer(struct kvm_vcpu *vcpu, u64 efer);
 int kvm_get_msr(struct kvm_vcpu *vcpu, u32 index, u64 *data);
 int kvm_set_msr(struct kvm_vcpu *vcpu, u32 index, u64 data);
+int kvm_emulate_rdmsr(struct kvm_vcpu *vcpu);
+int kvm_emulate_wrmsr(struct kvm_vcpu *vcpu);
 
 struct x86_emulate_ctxt;
 
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 030bc9f7b7a7..b033aebbcd30 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)
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index f4f4114e756f..b98a88dc8ca6 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -4866,37 +4866,12 @@  static int handle_cpuid(struct kvm_vcpu *vcpu)
 
 static int handle_rdmsr(struct kvm_vcpu *vcpu)
 {
-	u32 ecx = kvm_rcx_read(vcpu);
-	struct msr_data msr_info;
-
-	msr_info.index = ecx;
-	msr_info.host_initiated = false;
-	if (vmx_get_msr(vcpu, &msr_info)) {
-		trace_kvm_msr_read_ex(ecx);
-		kvm_inject_gp(vcpu, 0);
-		return 1;
-	}
-
-	trace_kvm_msr_read(ecx, msr_info.data);
-
-	kvm_rax_write(vcpu, msr_info.data & -1u);
-	kvm_rdx_write(vcpu, (msr_info.data >> 32) & -1u);
-	return kvm_skip_emulated_instruction(vcpu);
+	return kvm_emulate_rdmsr(vcpu);
 }
 
 static int handle_wrmsr(struct kvm_vcpu *vcpu)
 {
-	u32 ecx = kvm_rcx_read(vcpu);
-	u64 data = kvm_read_edx_eax(vcpu);
-
-	if (kvm_set_msr(vcpu, ecx, data) != 0) {
-		trace_kvm_msr_write_ex(ecx, data);
-		kvm_inject_gp(vcpu, 0);
-		return 1;
-	}
-
-	trace_kvm_msr_write(ecx, data);
-	return kvm_skip_emulated_instruction(vcpu);
+	return kvm_emulate_wrmsr(vcpu);
 }
 
 static int handle_tpr_below_threshold(struct kvm_vcpu *vcpu)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index a67730600803..7cd578d52611 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1434,6 +1434,41 @@  int kvm_set_msr(struct kvm_vcpu *vcpu, u32 index, u64 data)
 }
 EXPORT_SYMBOL_GPL(kvm_set_msr);
 
+int kvm_emulate_rdmsr(struct kvm_vcpu *vcpu)
+{
+	u32 ecx = kvm_rcx_read(vcpu);
+	u64 data;
+
+	if (kvm_get_msr(vcpu, ecx, &data)) {
+		trace_kvm_msr_read_ex(ecx);
+		kvm_inject_gp(vcpu, 0);
+		return 1;
+	}
+
+	trace_kvm_msr_read(ecx, data);
+
+	kvm_rax_write(vcpu, data & -1u);
+	kvm_rdx_write(vcpu, (data >> 32) & -1u);
+	return kvm_skip_emulated_instruction(vcpu);
+}
+EXPORT_SYMBOL_GPL(kvm_emulate_rdmsr);
+
+int kvm_emulate_wrmsr(struct kvm_vcpu *vcpu)
+{
+	u32 ecx = kvm_rcx_read(vcpu);
+	u64 data = kvm_read_edx_eax(vcpu);
+
+	if (kvm_set_msr(vcpu, ecx, data)) {
+		trace_kvm_msr_write_ex(ecx, data);
+		kvm_inject_gp(vcpu, 0);
+		return 1;
+	}
+
+	trace_kvm_msr_write(ecx, data);
+	return kvm_skip_emulated_instruction(vcpu);
+}
+EXPORT_SYMBOL_GPL(kvm_emulate_wrmsr);
+
 /*
  * Adapt set_msr() to msr_io()'s calling convention
  */