releases/4.9.120/kvm-x86-allow-userspace-to-define-the-microcode-version.patch

From foo@baz Tue Aug 14 16:14:56 CEST 2018
From: Wanpeng Li <wanpengli@tencent.com>
Date: Wed, 28 Feb 2018 14:03:31 +0800
Subject: KVM: X86: Allow userspace to define the microcode version

From: Wanpeng Li <wanpengli@tencent.com>

commit 518e7b94817abed94becfe6a44f1ece0d4745afe upstream

Linux (among the others) has checks to make sure that certain features
aren't enabled on a certain family/model/stepping if the microcode version
isn't greater than or equal to a known good version.

By exposing the real microcode version, we're preventing buggy guests that
don't check that they are running virtualized (i.e., they should trust the
hypervisor) from disabling features that are effectively not buggy.

Suggested-by: Filippo Sironi <sironi@amazon.de>
Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Cc: Liran Alon <liran.alon@oracle.com>
Cc: Nadav Amit <nadav.amit@gmail.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 arch/x86/include/asm/kvm_host.h |    1 +
 arch/x86/kvm/svm.c              |    4 +---
 arch/x86/kvm/vmx.c              |    1 +
 arch/x86/kvm/x86.c              |   11 +++++++++--
 4 files changed, 12 insertions(+), 5 deletions(-)

--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -486,6 +486,7 @@ struct kvm_vcpu_arch {
 	u64 smbase;
 	bool tpr_access_reporting;
 	u64 ia32_xss;
+	u64 microcode_version;
 
 	/*
 	 * Paging state of the vcpu
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -1569,6 +1569,7 @@ static void svm_vcpu_reset(struct kvm_vc
 	u32 dummy;
 	u32 eax = 1;
 
+	vcpu->arch.microcode_version = 0x01000065;
 	svm->spec_ctrl = 0;
 	svm->virt_spec_ctrl = 0;
 
@@ -3585,9 +3586,6 @@ static int svm_get_msr(struct kvm_vcpu *
 
 		msr_info->data = svm->virt_spec_ctrl;
 		break;
-	case MSR_IA32_UCODE_REV:
-		msr_info->data = 0x01000065;
-		break;
 	case MSR_F15H_IC_CFG: {
 
 		int family, model;
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -5481,6 +5481,7 @@ static void vmx_vcpu_reset(struct kvm_vc
 	u64 cr0;
 
 	vmx->rmode.vm86_active = 0;
+	vcpu->arch.microcode_version = 0x100000000ULL;
 	vmx->spec_ctrl = 0;
 
 	vmx->soft_vnmi_blocked = 0;
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1014,6 +1014,7 @@ static unsigned num_emulated_msrs;
  */
 static u32 msr_based_features[] = {
 	MSR_F10H_DECFG,
+	MSR_IA32_UCODE_REV,
 };
 
 static unsigned int num_msr_based_features;
@@ -1021,6 +1022,9 @@ static unsigned int num_msr_based_featur
 static int kvm_get_msr_feature(struct kvm_msr_entry *msr)
 {
 	switch (msr->index) {
+	case MSR_IA32_UCODE_REV:
+		rdmsrl(msr->index, msr->data);
+		break;
 	default:
 		if (kvm_x86_ops->get_msr_feature(msr))
 			return 1;
@@ -2157,13 +2161,16 @@ int kvm_set_msr_common(struct kvm_vcpu *
 
 	switch (msr) {
 	case MSR_AMD64_NB_CFG:
-	case MSR_IA32_UCODE_REV:
 	case MSR_IA32_UCODE_WRITE:
 	case MSR_VM_HSAVE_PA:
 	case MSR_AMD64_PATCH_LOADER:
 	case MSR_AMD64_BU_CFG2:
 		break;
 
+	case MSR_IA32_UCODE_REV:
+		if (msr_info->host_initiated)
+			vcpu->arch.microcode_version = data;
+		break;
 	case MSR_EFER:
 		return set_efer(vcpu, data);
 	case MSR_K7_HWCR:
@@ -2438,7 +2445,7 @@ int kvm_get_msr_common(struct kvm_vcpu *
 		msr_info->data = 0;
 		break;
 	case MSR_IA32_UCODE_REV:
-		msr_info->data = 0x100000000ULL;
+		msr_info->data = vcpu->arch.microcode_version;
 		break;
 	case MSR_MTRRcap:
 	case 0x200 ... 0x2ff: