KVM: x86: Invert emulation re-execute behavior to make it opt-in

Re-execution of an instruction after emulation decode failure is
intended to be used only when emulating shadow page accesses.  Invert
the flag to make allowing re-execution opt-in since that behavior is
by far in the minority.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: stable@vger.kernel.org
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>

arch/x86/include/asm/kvm_host.h

@@ -1238,7 +1238,7 @@ enum emulation_result {
 #define EMULTYPE_TRAP_UD	    (1 << 1)
 #define EMULTYPE_SKIP		    (1 << 2)
 #define EMULTYPE_RETRY		    (1 << 3)
-#define EMULTYPE_NO_REEXECUTE	    (1 << 4)
+#define EMULTYPE_ALLOW_REEXECUTE    (1 << 4)
 #define EMULTYPE_NO_UD_ON_FAIL	    (1 << 5)
 #define EMULTYPE_VMWARE		    (1 << 6)
 int x86_emulate_instruction(struct kvm_vcpu *vcpu, unsigned long cr2,
@@ -1247,15 +1247,13 @@ int x86_emulate_instruction(struct kvm_vcpu *vcpu, unsigned long cr2,
 static inline int emulate_instruction(struct kvm_vcpu *vcpu,
 			int emulation_type)
 {
-	return x86_emulate_instruction(vcpu, 0,
-			emulation_type | EMULTYPE_NO_REEXECUTE, NULL, 0);
+	return x86_emulate_instruction(vcpu, 0, emulation_type, NULL, 0);
 }
 
 static inline int kvm_emulate_instruction_from_buffer(struct kvm_vcpu *vcpu,
 						      void *insn, int insn_len)
 {
-	return x86_emulate_instruction(vcpu, 0, EMULTYPE_NO_REEXECUTE,
-				       insn, insn_len);
+	return x86_emulate_instruction(vcpu, 0, 0, insn, insn_len);
 }
 
 void kvm_enable_efer_bits(u64);

arch/x86/kvm/mmu.c

@@ -5217,7 +5217,7 @@ static int make_mmu_pages_available(struct kvm_vcpu *vcpu)
 int kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gva_t cr2, u64 error_code,
 		       void *insn, int insn_len)
 {
-	int r, emulation_type = EMULTYPE_RETRY;
+	int r, emulation_type = EMULTYPE_RETRY | EMULTYPE_ALLOW_REEXECUTE;
 	enum emulation_result er;
 	bool direct = vcpu->arch.mmu.direct_map;
 

arch/x86/kvm/x86.c

@@ -5870,7 +5870,7 @@ static bool reexecute_instruction(struct kvm_vcpu *vcpu, gva_t cr2,
 	gpa_t gpa = cr2;
 	kvm_pfn_t pfn;
 
-	if (emulation_type & EMULTYPE_NO_REEXECUTE)
+	if (!(emulation_type & EMULTYPE_ALLOW_REEXECUTE))
 		return false;
 
 	if (!vcpu->arch.mmu.direct_map) {