[PATCH v2 06/14] KVM: x86: Add explicit flag for forced emulation on #UD

[Sean Christopherson]

Add an explicit emulation type for forced #UD emulation and use it to
detect that KVM should unconditionally inject a #UD instead of falling
into its standard emulation failure handling.

Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
---
 arch/x86/include/asm/kvm_host.h | 1 +
 arch/x86/kvm/x86.c              | 5 +++--
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index d1d5b5ca1195..a38c93362945 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1318,6 +1318,7 @@ enum emulation_result {
 #define EMULTYPE_TRAP_UD	    (1 << 1)
 #define EMULTYPE_SKIP		    (1 << 2)
 #define EMULTYPE_ALLOW_RETRY	    (1 << 3)
+#define EMULTYPE_TRAP_UD_FORCED	    (1 << 4)
 #define EMULTYPE_VMWARE_GP	    (1 << 5)
 int kvm_emulate_instruction(struct kvm_vcpu *vcpu, int emulation_type);
 int kvm_emulate_instruction_from_buffer(struct kvm_vcpu *vcpu,
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 228ca71d5b01..a1f9e36b2d58 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5337,7 +5337,7 @@ int handle_ud(struct kvm_vcpu *vcpu)
 				sig, sizeof(sig), &e) == 0 &&
 	    memcmp(sig, "\xf\xbkvm", sizeof(sig)) == 0) {
 		kvm_rip_write(vcpu, kvm_rip_read(vcpu) + sizeof(sig));
-		emul_type = 0;
+		emul_type = EMULTYPE_TRAP_UD_FORCED;
 	}
 
 	er = kvm_emulate_instruction(vcpu, emul_type);
@@ -6532,7 +6532,8 @@ int x86_emulate_instruction(struct kvm_vcpu *vcpu,
 		trace_kvm_emulate_insn_start(vcpu);
 		++vcpu->stat.insn_emulation;
 		if (r != EMULATION_OK)  {
-			if (emulation_type & EMULTYPE_TRAP_UD)
+			if ((emulation_type & EMULTYPE_TRAP_UD) ||
+			    (emulation_type & EMULTYPE_TRAP_UD_FORCED))
 				return EMULATE_FAIL;
 			if (reexecute_instruction(vcpu, cr2, write_fault_to_spt,
 						emulation_type))
-- 
2.22.0