KVM: x86: pass host_initiated to functions that read MSRs

SMBASE is only readable from SMM for the VCPU, but it must be always
accessible if userspace is accessing it.  Thus, all functions that
read MSRs are changed to accept a struct msr_data; the host_initiated
and index fields are pre-initialized, while the data field is filled
on return.

Reviewed-by: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 30 insertions, 32 deletions

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 9cf5030927d5..b5b7b8ab2f59 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -2622,76 +2622,69 @@ static int vmx_get_vmx_msr(struct kvm_vcpu *vcpu, u32 msr_index, u64 *pdata)
  * Returns 0 on success, non-0 otherwise.
  * Assumes vcpu_load() was already called.
  */
-static int vmx_get_msr(struct kvm_vcpu *vcpu, u32 msr_index, u64 *pdata)
+static int vmx_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 {
-	u64 data;
 	struct shared_msr_entry *msr;
 
-	if (!pdata) {
-		printk(KERN_ERR "BUG: get_msr called with NULL pdata\n");
-		return -EINVAL;
-	}
-
-	switch (msr_index) {
+	switch (msr_info->index) {
 #ifdef CONFIG_X86_64
 	case MSR_FS_BASE:
-		data = vmcs_readl(GUEST_FS_BASE);
+		msr_info->data = vmcs_readl(GUEST_FS_BASE);
 		break;
 	case MSR_GS_BASE:
-		data = vmcs_readl(GUEST_GS_BASE);
+		msr_info->data = vmcs_readl(GUEST_GS_BASE);
 		break;
 	case MSR_KERNEL_GS_BASE:
 		vmx_load_host_state(to_vmx(vcpu));
-		data = to_vmx(vcpu)->msr_guest_kernel_gs_base;
+		msr_info->data = to_vmx(vcpu)->msr_guest_kernel_gs_base;
 		break;
 #endif
 	case MSR_EFER:
-		return kvm_get_msr_common(vcpu, msr_index, pdata);
+		return kvm_get_msr_common(vcpu, msr_info);
 	case MSR_IA32_TSC:
-		data = guest_read_tsc();
+		msr_info->data = guest_read_tsc();
 		break;
 	case MSR_IA32_SYSENTER_CS:
-		data = vmcs_read32(GUEST_SYSENTER_CS);
+		msr_info->data = vmcs_read32(GUEST_SYSENTER_CS);
 		break;
 	case MSR_IA32_SYSENTER_EIP:
-		data = vmcs_readl(GUEST_SYSENTER_EIP);
+		msr_info->data = vmcs_readl(GUEST_SYSENTER_EIP);
 		break;
 	case MSR_IA32_SYSENTER_ESP:
-		data = vmcs_readl(GUEST_SYSENTER_ESP);
+		msr_info->data = vmcs_readl(GUEST_SYSENTER_ESP);
 		break;
 	case MSR_IA32_BNDCFGS:
 		if (!vmx_mpx_supported())
 			return 1;
-		data = vmcs_read64(GUEST_BNDCFGS);
+		msr_info->data = vmcs_read64(GUEST_BNDCFGS);
 		break;
 	case MSR_IA32_FEATURE_CONTROL:
 		if (!nested_vmx_allowed(vcpu))
 			return 1;
-		data = to_vmx(vcpu)->nested.msr_ia32_feature_control;
+		msr_info->data = to_vmx(vcpu)->nested.msr_ia32_feature_control;
 		break;
 	case MSR_IA32_VMX_BASIC ... MSR_IA32_VMX_VMFUNC:
 		if (!nested_vmx_allowed(vcpu))
 			return 1;
-		return vmx_get_vmx_msr(vcpu, msr_index, pdata);
+		return vmx_get_vmx_msr(vcpu, msr_info->index, &msr_info->data);
 	case MSR_IA32_XSS:
 		if (!vmx_xsaves_supported())
 			return 1;
-		data = vcpu->arch.ia32_xss;
+		msr_info->data = vcpu->arch.ia32_xss;
 		break;
 	case MSR_TSC_AUX:
 		if (!to_vmx(vcpu)->rdtscp_enabled)
 			return 1;
 		/* Otherwise falls through */
 	default:
-		msr = find_msr_entry(to_vmx(vcpu), msr_index);
+		msr = find_msr_entry(to_vmx(vcpu), msr_info->index);
 		if (msr) {
-			data = msr->data;
+			msr_info->data = msr->data;
 			break;
 		}
-		return kvm_get_msr_common(vcpu, msr_index, pdata);
+		return kvm_get_msr_common(vcpu, msr_info);
 	}
 
-	*pdata = data;
 	return 0;
 }
 
@@ -5473,19 +5466,21 @@ static int handle_cpuid(struct kvm_vcpu *vcpu)
 static int handle_rdmsr(struct kvm_vcpu *vcpu)
 {
 	u32 ecx = vcpu->arch.regs[VCPU_REGS_RCX];
-	u64 data;
+	struct msr_data msr_info;
 
-	if (vmx_get_msr(vcpu, ecx, &data)) {
+	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, data);
+	trace_kvm_msr_read(ecx, msr_info.data);
 
 	/* FIXME: handling of bits 32:63 of rax, rdx */
-	vcpu->arch.regs[VCPU_REGS_RAX] = data & -1u;
-	vcpu->arch.regs[VCPU_REGS_RDX] = (data >> 32) & -1u;
+	vcpu->arch.regs[VCPU_REGS_RAX] = msr_info.data & -1u;
+	vcpu->arch.regs[VCPU_REGS_RDX] = (msr_info.data >> 32) & -1u;
 	skip_emulated_instruction(vcpu);
 	return 1;
 }
@@ -9147,6 +9142,7 @@ static int nested_vmx_store_msr(struct kvm_vcpu *vcpu, u64 gpa, u32 count)
 	struct vmx_msr_entry e;
 
 	for (i = 0; i < count; i++) {
+		struct msr_data msr_info;
 		if (kvm_read_guest(vcpu->kvm,
 				   gpa + i * sizeof(e),
 				   &e, 2 * sizeof(u32))) {
@@ -9161,7 +9157,9 @@ static int nested_vmx_store_msr(struct kvm_vcpu *vcpu, u64 gpa, u32 count)
 				__func__, i, e.index, e.reserved);
 			return -EINVAL;
 		}
-		if (kvm_get_msr(vcpu, e.index, &e.value)) {
+		msr_info.host_initiated = false;
+		msr_info.index = e.index;
+		if (kvm_get_msr(vcpu, &msr_info)) {
 			pr_warn_ratelimited(
 				"%s cannot read MSR (%u, 0x%x)\n",
 				__func__, i, e.index);
@@ -9170,10 +9168,10 @@ static int nested_vmx_store_msr(struct kvm_vcpu *vcpu, u64 gpa, u32 count)
 		if (kvm_write_guest(vcpu->kvm,
 				    gpa + i * sizeof(e) +
 					offsetof(struct vmx_msr_entry, value),
-				    &e.value, sizeof(e.value))) {
+				    &msr_info.data, sizeof(msr_info.data))) {
 			pr_warn_ratelimited(
 				"%s cannot write MSR (%u, 0x%x, 0x%llx)\n",
-				__func__, i, e.index, e.value);
+				__func__, i, e.index, msr_info.data);
 			return -EINVAL;
 		}
 	}