KVM: x86: Move EMULTYPE_ALLOW_RETRY_PF to x86_emulate_instruction()

Move the sanity checks for EMULTYPE_ALLOW_RETRY_PF to the top of
x86_emulate_instruction().  In addition to deduplicating a small amount
of code, this makes the connection between EMULTYPE_ALLOW_RETRY_PF and
EMULTYPE_PF even more explicit, and will allow dropping retry_instruction()
entirely.
Reviewed-by: Yuan Yao <yuan.yao@intel.com>
Link: https://lore.kernel.org/r/20240831001538.336683-11-seanjc@google.comSigned-off-by: Sean Christopherson <seanjc@google.com>

arch/x86/kvm/x86.c

@@ -8870,10 +8870,6 @@ static bool reexecute_instruction(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
 	if (!(emulation_type & EMULTYPE_ALLOW_RETRY_PF))
 		return false;
 
-	if (WARN_ON_ONCE(is_guest_mode(vcpu)) ||
-	    WARN_ON_ONCE(!(emulation_type & EMULTYPE_PF)))
-		return false;
-
 	if (!vcpu->arch.mmu->root_role.direct) {
 		/*
 		 * Write permission should be allowed since only
@@ -8942,10 +8938,6 @@ static bool retry_instruction(struct x86_emulate_ctxt *ctxt,
 	if (!(emulation_type & EMULTYPE_ALLOW_RETRY_PF))
 		return false;
 
-	if (WARN_ON_ONCE(is_guest_mode(vcpu)) ||
-	    WARN_ON_ONCE(!(emulation_type & EMULTYPE_PF)))
-		return false;
-
 	if (x86_page_table_writing_insn(ctxt))
 		return false;
 
@@ -9148,6 +9140,11 @@ int x86_emulate_instruction(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
 	struct x86_emulate_ctxt *ctxt = vcpu->arch.emulate_ctxt;
 	bool writeback = true;
 
+	if ((emulation_type & EMULTYPE_ALLOW_RETRY_PF) &&
+	    (WARN_ON_ONCE(is_guest_mode(vcpu)) ||
+	     WARN_ON_ONCE(!(emulation_type & EMULTYPE_PF))))
+		emulation_type &= ~EMULTYPE_ALLOW_RETRY_PF;
+
 	r = kvm_check_emulate_insn(vcpu, emulation_type, insn, insn_len);
 	if (r != X86EMUL_CONTINUE) {
 		if (r == X86EMUL_RETRY_INSTR || r == X86EMUL_PROPAGATE_FAULT)