1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * ucall support. A ucall is a "hypercall to userspace".
4  *
5  * Copyright (C) 2019 Red Hat, Inc.
6  */
7 #include "kvm_util.h"
8 
9 void ucall_init(struct kvm_vm *vm, void *arg)
10 {
11 }
12 
13 void ucall_uninit(struct kvm_vm *vm)
14 {
15 }
16 
17 void ucall(uint64_t cmd, int nargs, ...)
18 {
19 	struct ucall uc = {
20 		.cmd = cmd,
21 	};
22 	va_list va;
23 	int i;
24 
25 	nargs = min(nargs, UCALL_MAX_ARGS);
26 
27 	va_start(va, nargs);
28 	for (i = 0; i < nargs; ++i)
29 		uc.args[i] = va_arg(va, uint64_t);
30 	va_end(va);
31 
32 	/* Exit via DIAGNOSE 0x501 (normally used for breakpoints) */
33 	asm volatile ("diag 0,%0,0x501" : : "a"(&uc) : "memory");
34 }
35 
36 uint64_t get_ucall(struct kvm_vcpu *vcpu, struct ucall *uc)
37 {
38 	struct kvm_run *run = vcpu->run;
39 	struct ucall ucall = {};
40 
41 	if (uc)
42 		memset(uc, 0, sizeof(*uc));
43 
44 	if (run->exit_reason == KVM_EXIT_S390_SIEIC &&
45 	    run->s390_sieic.icptcode == 4 &&
46 	    (run->s390_sieic.ipa >> 8) == 0x83 &&    /* 0x83 means DIAGNOSE */
47 	    (run->s390_sieic.ipb >> 16) == 0x501) {
48 		int reg = run->s390_sieic.ipa & 0xf;
49 
50 		memcpy(&ucall, addr_gva2hva(vcpu->vm, run->s.regs.gprs[reg]),
51 		       sizeof(ucall));
52 
53 		vcpu_run_complete_io(vcpu);
54 		if (uc)
55 			memcpy(uc, &ucall, sizeof(ucall));
56 	}
57 
58 	return ucall.cmd;
59 }
60