[PATCH v2 12/15] KVM: x86: Harden is_64_bit_hypercall() against bugs on 32-bit kernels

[Sean Christopherson <seanjc@google.com>]

Unconditionally return %false for is_64_bit_hypercall() on 32-bit kernels
to guard against incorrectly setting guest_state_protected, and because
in a (very) hypothetical world where 32-bit KVM supports protected guests,
assuming a hypercall was made in 64-bit mode is flat out wrong.

Reviewed-by: Kai Huang <kai.huang@intel.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 arch/x86/kvm/regs.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/x86/kvm/regs.h b/arch/x86/kvm/regs.h
index 52bed14f43e3..d4d2a47a4968 100644
--- a/arch/x86/kvm/regs.h
+++ b/arch/x86/kvm/regs.h
@@ -39,12 +39,16 @@ static inline bool is_64_bit_mode(struct kvm_vcpu *vcpu)
 
 static inline bool is_64_bit_hypercall(struct kvm_vcpu *vcpu)
 {
+#ifdef CONFIG_X86_64
 	/*
 	 * If running with protected guest state, the CS register is not
 	 * accessible. The hypercall register values will have had to been
 	 * provided in 64-bit mode, so assume the guest is in 64-bit.
 	 */
 	return vcpu->arch.guest_state_protected || is_64_bit_mode(vcpu);
+#else
+	return false;
+#endif
 }
 
 static __always_inline unsigned long kvm_reg_mode_mask(struct kvm_vcpu *vcpu)
-- 
2.54.0.563.g4f69b47b94-goog