x86/kvm: add MSR_IA32_SPEC_CTRL and MSR_IA32_PRED_CMD to kvm

CVE-2017-5715 (Spectre v2 Intel)

Add field to access guest MSR_IA332_SPEC_CTRL and MSR_IA32_PRED_CMD state.
Signed-off-by: Wei Wang <wei.w.wang@intel.com>
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Andy Whitcroft <apw@canonical.com>
(backported from commit f93ba2a9b5ab2c275e9adc10876cc0425a33eec0)
Signed-off-by: Andy Whitcroft <apw@canonical.com>
Acked-by: Colin Ian King <colin.king@canonical.com>
Acked-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

arch/x86/include/asm/kvm_host.h

@@ -557,6 +557,8 @@ struct kvm_vcpu_arch {
 	u64 mcg_ctl;
 	u64 *mce_banks;
 
+	u64 spec_ctrl;
+
 	/* Cache MMIO info */
 	u64 mmio_gva;
 	unsigned access;

arch/x86/kvm/vmx.c

@@ -49,6 +49,7 @@
 #include <asm/apic.h>
 #include <asm/irq_remapping.h>
 #include <asm/nospec-branch.h>
+#include <asm/microcode.h>
 
 #include "trace.h"
 #include "pmu.h"
@@ -2804,6 +2805,9 @@ static int vmx_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 	case MSR_IA32_TSC:
 		msr_info->data = guest_read_tsc(vcpu);
 		break;
+	case MSR_IA32_SPEC_CTRL:
+		msr_info->data = vcpu->arch.spec_ctrl;
+		break;
 	case MSR_IA32_SYSENTER_CS:
 		msr_info->data = vmcs_read32(GUEST_SYSENTER_CS);
 		break;
@@ -2903,6 +2907,9 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 	case MSR_IA32_TSC:
 		kvm_write_tsc(vcpu, msr_info);
 		break;
+	case MSR_IA32_SPEC_CTRL:
+		vcpu->arch.spec_ctrl = msr_info->data;
+		break;
 	case MSR_IA32_CR_PAT:
 		if (vmcs_config.vmentry_ctrl & VM_ENTRY_LOAD_IA32_PAT) {
 			if (!kvm_mtrr_valid(vcpu, MSR_IA32_CR_PAT, data))
@@ -5681,6 +5688,7 @@ static int handle_rdmsr(struct kvm_vcpu *vcpu)
 
 	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);
@@ -6274,6 +6282,8 @@ static __init int hardware_setup(void)
 	vmx_disable_intercept_for_msr(MSR_IA32_SYSENTER_CS, false);
 	vmx_disable_intercept_for_msr(MSR_IA32_SYSENTER_ESP, false);
 	vmx_disable_intercept_for_msr(MSR_IA32_SYSENTER_EIP, false);
+	vmx_disable_intercept_for_msr(MSR_IA32_SPEC_CTRL, false);
+	vmx_disable_intercept_for_msr(MSR_IA32_PRED_CMD, false);
 
 	memcpy(vmx_msr_bitmap_legacy_x2apic,
 			vmx_msr_bitmap_legacy, PAGE_SIZE);

arch/x86/kvm/x86.c

@@ -960,7 +960,7 @@ static u32 msrs_to_save[] = {
 	MSR_CSTAR, MSR_KERNEL_GS_BASE, MSR_SYSCALL_MASK, MSR_LSTAR,
 #endif
 	MSR_IA32_TSC, MSR_IA32_CR_PAT, MSR_VM_HSAVE_PA,
-	MSR_IA32_FEATURE_CONTROL, MSR_IA32_BNDCFGS, MSR_TSC_AUX,
+	MSR_IA32_FEATURE_CONTROL, MSR_IA32_BNDCFGS, MSR_TSC_AUX, MSR_IA32_SPEC_CTRL,
 };
 
 static unsigned num_msrs_to_save;