KVM: x86: Add code to track call origin for msr assignment

In order to track who initiated the call (host or guest) to modify an msr
value I have changed function call parameters along the call path. The
specific change is to add a struct pointer parameter that points to (index,
data, caller) information rather than having this information passed as
individual parameters.

The initial use for this capability is for updating the IA32_TSC_ADJUST msr
while setting the tsc value. It is anticipated that this capability is
useful for other tasks.

Signed-off-by: Will Auld <[e-mail]>
Signed-off-by: Marcelo Tosatti <[e-mail]>

arch/x86/include/asm/kvm_host.h

···
 
 struct x86_instruction_info;
 
+struct msr_data {
+	bool host_initiated;
+	u32 index;
+	u64 data;
+};
+
 struct kvm_x86_ops {
 	int (*cpu_has_kvm_support)(void);          /* __init */
 	int (*disabled_by_bios)(void);             /* __init */
···
 
 	void (*update_db_bp_intercept)(struct kvm_vcpu *vcpu);
 	int (*get_msr)(struct kvm_vcpu *vcpu, u32 msr_index, u64 *pdata);
-	int (*set_msr)(struct kvm_vcpu *vcpu, u32 msr_index, u64 data);
+	int (*set_msr)(struct kvm_vcpu *vcpu, struct msr_data *msr);
 	u64 (*get_segment_base)(struct kvm_vcpu *vcpu, int seg);
 	void (*get_segment)(struct kvm_vcpu *vcpu,
 			    struct kvm_segment *var, int seg);
···
 
 void kvm_enable_efer_bits(u64);
 int kvm_get_msr(struct kvm_vcpu *vcpu, u32 msr_index, u64 *data);
-int kvm_set_msr(struct kvm_vcpu *vcpu, u32 msr_index, u64 data);
+int kvm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr);
 
 struct x86_emulate_ctxt;
 
···
 int kvm_set_xcr(struct kvm_vcpu *vcpu, u32 index, u64 xcr);
 
 int kvm_get_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata);
-int kvm_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 data);
+int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr);
 
 unsigned long kvm_get_rflags(struct kvm_vcpu *vcpu);
 void kvm_set_rflags(struct kvm_vcpu *vcpu, unsigned long rflags);

arch/x86/kvm/svm.c

···
 	return 0;
 }
 
-static int svm_set_msr(struct kvm_vcpu *vcpu, unsigned ecx, u64 data)
+static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr)
 {
 	struct vcpu_svm *svm = to_svm(vcpu);
 
+	u32 ecx = msr->index;
+	u64 data = msr->data;
 	switch (ecx) {
 	case MSR_IA32_TSC:
-		kvm_write_tsc(vcpu, data);
+		kvm_write_tsc(vcpu, msr);
 		break;
 	case MSR_STAR:
 		svm->vmcb->save.star = data;
···
 		vcpu_unimpl(vcpu, "unimplemented wrmsr: 0x%x data 0x%llx\n", ecx, data);
 		break;
 	default:
-		return kvm_set_msr_common(vcpu, ecx, data);
+		return kvm_set_msr_common(vcpu, msr);
 	}
 	return 0;
 }
 
 static int wrmsr_interception(struct vcpu_svm *svm)
 {
+	struct msr_data msr;
 	u32 ecx = svm->vcpu.arch.regs[VCPU_REGS_RCX];
 	u64 data = (svm->vcpu.arch.regs[VCPU_REGS_RAX] & -1u)
 		| ((u64)(svm->vcpu.arch.regs[VCPU_REGS_RDX] & -1u) << 32);
 
+	msr.data = data;
+	msr.index = ecx;
+	msr.host_initiated = false;
 
 	svm->next_rip = kvm_rip_read(&svm->vcpu) + 2;
-	if (svm_set_msr(&svm->vcpu, ecx, data)) {
+	if (svm_set_msr(&svm->vcpu, &msr)) {
 		trace_kvm_msr_write_ex(ecx, data);
 		kvm_inject_gp(&svm->vcpu, 0);
 	} else {

arch/x86/kvm/vmx.c

···
  * Returns 0 on success, non-0 otherwise.
  * Assumes vcpu_load() was already called.
  */
-static int vmx_set_msr(struct kvm_vcpu *vcpu, u32 msr_index, u64 data)
+static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 {
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
 	struct shared_msr_entry *msr;
 	int ret = 0;
+	u32 msr_index = msr_info->index;
+	u64 data = msr_info->data;
 
 	switch (msr_index) {
 	case MSR_EFER:
-		ret = kvm_set_msr_common(vcpu, msr_index, data);
+		ret = kvm_set_msr_common(vcpu, msr_info);
 		break;
 #ifdef CONFIG_X86_64
 	case MSR_FS_BASE:
···
 		vmcs_writel(GUEST_SYSENTER_ESP, data);
 		break;
 	case MSR_IA32_TSC:
-		kvm_write_tsc(vcpu, data);
+		kvm_write_tsc(vcpu, msr_info);
 		break;
 	case MSR_IA32_CR_PAT:
 		if (vmcs_config.vmentry_ctrl & VM_ENTRY_LOAD_IA32_PAT) {
···
 			vcpu->arch.pat = data;
 			break;
 		}
-		ret = kvm_set_msr_common(vcpu, msr_index, data);
+		ret = kvm_set_msr_common(vcpu, msr_info);
 		break;
 	case MSR_TSC_AUX:
 		if (!vmx->rdtscp_enabled)
···
 			}
 			break;
 		}
-		ret = kvm_set_msr_common(vcpu, msr_index, data);
+		ret = kvm_set_msr_common(vcpu, msr_info);
 	}
 
 	return ret;
···
 
 static int handle_wrmsr(struct kvm_vcpu *vcpu)
 {
+	struct msr_data msr;
 	u32 ecx = vcpu->arch.regs[VCPU_REGS_RCX];
 	u64 data = (vcpu->arch.regs[VCPU_REGS_RAX] & -1u)
 		| ((u64)(vcpu->arch.regs[VCPU_REGS_RDX] & -1u) << 32);
 
-	if (vmx_set_msr(vcpu, ecx, data) != 0) {
+	msr.data = data;
+	msr.index = ecx;
+	msr.host_initiated = false;
+	if (vmx_set_msr(vcpu, &msr) != 0) {
 		trace_kvm_msr_write_ex(ecx, data);
 		kvm_inject_gp(vcpu, 0);
 		return 1;

arch/x86/kvm/x86.c

···
  * Returns 0 on success, non-0 otherwise.
  * Assumes vcpu_load() was already called.
  */
-int kvm_set_msr(struct kvm_vcpu *vcpu, u32 msr_index, u64 data)
+int kvm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr)
 {
-	return kvm_x86_ops->set_msr(vcpu, msr_index, data);
+	return kvm_x86_ops->set_msr(vcpu, msr);
 }
 
 /*
···
  */
 static int do_set_msr(struct kvm_vcpu *vcpu, unsigned index, u64 *data)
 {
-	return kvm_set_msr(vcpu, index, *data);
+	struct msr_data msr;
+
+	msr.data = *data;
+	msr.index = index;
+	msr.host_initiated = true;
+	return kvm_set_msr(vcpu, &msr);
 }
 
 #ifdef CONFIG_X86_64
···
 #endif
 }
 
-void kvm_write_tsc(struct kvm_vcpu *vcpu, u64 data)
+void kvm_write_tsc(struct kvm_vcpu *vcpu, struct msr_data *msr)
 {
 	struct kvm *kvm = vcpu->kvm;
 	u64 offset, ns, elapsed;
 	unsigned long flags;
 	s64 usdiff;
 	bool matched;
+	u64 data = msr->data;
 
 	raw_spin_lock_irqsave(&kvm->arch.tsc_write_lock, flags);
 	offset = kvm_x86_ops->compute_tsc_offset(vcpu, data);
···
 		&vcpu->arch.st.steal, sizeof(struct kvm_steal_time));
 }
 
-int kvm_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 data)
+int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 {
 	bool pr = false;
+	u32 msr = msr_info->index;
+	u64 data = msr_info->data;
 
 	switch (msr) {
 	case MSR_EFER:
···
 static int emulator_set_msr(struct x86_emulate_ctxt *ctxt,
 			    u32 msr_index, u64 data)
 {
-	return kvm_set_msr(emul_to_vcpu(ctxt), msr_index, data);
+	struct msr_data msr;
+
+	msr.data = data;
+	msr.index = msr_index;
+	msr.host_initiated = false;
+	return kvm_set_msr(emul_to_vcpu(ctxt), &msr);
 }
 
 static int emulator_read_pmc(struct x86_emulate_ctxt *ctxt,
···
 int kvm_arch_vcpu_postcreate(struct kvm_vcpu *vcpu)
 {
 	int r;
+	struct msr_data msr;
 
 	r = vcpu_load(vcpu);
 	if (r)
 		return r;
-	kvm_write_tsc(vcpu, 0);
+	msr.data = 0x0;
+	msr.index = MSR_IA32_TSC;
+	msr.host_initiated = true;
+	kvm_write_tsc(vcpu, &msr);
 	vcpu_put(vcpu);
 
 	return r;

arch/x86/kvm/x86.h

···
 void kvm_after_handle_nmi(struct kvm_vcpu *vcpu);
 int kvm_inject_realmode_interrupt(struct kvm_vcpu *vcpu, int irq, int inc_eip);
 
-void kvm_write_tsc(struct kvm_vcpu *vcpu, u64 data);
+void kvm_write_tsc(struct kvm_vcpu *vcpu, struct msr_data *msr);
 
 int kvm_read_guest_virt(struct x86_emulate_ctxt *ctxt,
 	gva_t addr, void *val, unsigned int bytes,