[RFC PATCH v3 17/59] KVM: x86: Add flag to disallow #MC injection / KVM_X86_SETUP_MCE

[isaku . yamahata]

From: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>

Add a flag to disallow MCE injection and reject KVM_X86_SETUP_MCE with
-EINVAL when set.  TDX doesn't support injecting exceptions, including
(virtual) #MCs.

Co-developed-by: Kai Huang <kai.huang@xxxxxxxxxxxxxxx>
Signed-off-by: Kai Huang <kai.huang@xxxxxxxxxxxxxxx>
Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
Signed-off-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
---
 arch/x86/include/asm/kvm_host.h |  1 +
 arch/x86/kvm/x86.c              | 14 +++++++-------
 2 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index ebc4de32bf0e..e912e1e853ef 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1142,6 +1142,7 @@ struct kvm_arch {
 
 	bool bus_lock_detection_enabled;
 	bool irq_injection_disallowed;
+	bool mce_injection_disallowed;
 	/*
 	 * If exit_on_emulation_error is set, and the in-kernel instruction
 	 * emulator fails to emulate an instruction, allow userspace
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index b399e64e8863..fefa4602e879 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4561,15 +4561,16 @@ static int vcpu_ioctl_tpr_access_reporting(struct kvm_vcpu *vcpu,
 static int kvm_vcpu_ioctl_x86_setup_mce(struct kvm_vcpu *vcpu,
 					u64 mcg_cap)
 {
-	int r;
 	unsigned bank_num = mcg_cap & 0xff, bank;
 
-	r = -EINVAL;
+	if (vcpu->kvm->arch.mce_injection_disallowed)
+		return -EINVAL;
+
 	if (!bank_num || bank_num > KVM_MAX_MCE_BANKS)
-		goto out;
+		return -EINVAL;
 	if (mcg_cap & ~(kvm_mce_cap_supported | 0xff | 0xff0000))
-		goto out;
-	r = 0;
+		return -EINVAL;
+
 	vcpu->arch.mcg_cap = mcg_cap;
 	/* Init IA32_MCG_CTL to all 1s */
 	if (mcg_cap & MCG_CTL_P)
@@ -4579,8 +4580,7 @@ static int kvm_vcpu_ioctl_x86_setup_mce(struct kvm_vcpu *vcpu,
 		vcpu->arch.mce_banks[bank*4] = ~(u64)0;
 
 	static_call(kvm_x86_setup_mce)(vcpu);
-out:
-	return r;
+	return 0;
 }
 
 static int kvm_vcpu_ioctl_x86_set_mce(struct kvm_vcpu *vcpu,
-- 
2.25.1