linux-kernel - [PATCH 2/2] KVM: VMX: Inject #GP, not #UD, if SGX2 ENCLS leafs are unsupported

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Date:   Wed,  5 Apr 2023 16:45:56 -0700
From:   Sean Christopherson <seanjc@...gle.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Binbin Wu <binbin.wu@...ux.intel.com>,
        Kai Huang <kai.huang@...el.com>
Subject: [PATCH 2/2] KVM: VMX: Inject #GP, not #UD, if SGX2 ENCLS leafs are unsupported

Per Intel's SDM, unsupported ENCLS leafs result in a #GP, not a #UD.
SGX1 is a special snowflake as the SGX1 flag is used by the CPU as a
"soft" disable, e.g. if software disables machine check reporting, i.e.
having SGX but not SGX1 is effectively "SGX completely unsupported" and
and thus #UDs.

Fixes: 9798adbc04cf ("KVM: VMX: Frame in ENCLS handler for SGX virtualization")
Cc: Binbin Wu <binbin.wu@...ux.intel.com>
Cc: Kai Huang <kai.huang@...el.com>
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/vmx/sgx.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kvm/vmx/sgx.c b/arch/x86/kvm/vmx/sgx.c
index f881f6ff6408..1c092ab89c33 100644
--- a/arch/x86/kvm/vmx/sgx.c
+++ b/arch/x86/kvm/vmx/sgx.c
@@ -350,11 +350,12 @@ static int handle_encls_einit(struct kvm_vcpu *vcpu)
 
 static inline bool encls_leaf_enabled_in_guest(struct kvm_vcpu *vcpu, u32 leaf)
 {
-	if (!enable_sgx || !guest_cpuid_has(vcpu, X86_FEATURE_SGX))
-		return false;
-
+	/*
+	 * ENCLS #UDs if SGX1 isn't supported, i.e. this point will be reached
+	 * if and only if the SGX1 leafs are enabled.
+	 */
 	if (leaf >= ECREATE && leaf <= ETRACK)
-		return guest_cpuid_has(vcpu, X86_FEATURE_SGX1);
+		return true;
 
 	if (leaf >= EAUG && leaf <= EMODT)
 		return guest_cpuid_has(vcpu, X86_FEATURE_SGX2);
@@ -373,9 +374,11 @@ int handle_encls(struct kvm_vcpu *vcpu)
 {
 	u32 leaf = (u32)kvm_rax_read(vcpu);
 
-	if (!encls_leaf_enabled_in_guest(vcpu, leaf)) {
+	if (!enable_sgx || !guest_cpuid_has(vcpu, X86_FEATURE_SGX) ||
+	    !guest_cpuid_has(vcpu, X86_FEATURE_SGX1)) {
 		kvm_queue_exception(vcpu, UD_VECTOR);
-	} else if (!sgx_enabled_in_guest_bios(vcpu) || !is_paging(vcpu)) {
+	} else if (!encls_leaf_enabled_in_guest(vcpu, leaf) ||
+		   !sgx_enabled_in_guest_bios(vcpu) || !is_paging(vcpu)) {
 		kvm_inject_gp(vcpu, 0);
 	} else {
 		if (leaf == ECREATE)
-- 
2.40.0.348.gf938b09366-goog