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
9void ucall_init(struct kvm_vm *vm, void *arg)
10{
11}
12
13void ucall_uninit(struct kvm_vm *vm)
14{
15}
16
17void 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 = nargs <= UCALL_MAX_ARGS ? 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
36uint64_t get_ucall(struct kvm_vm *vm, uint32_t vcpu_id, struct ucall *uc)
37{
38	struct kvm_run *run = vcpu_state(vm, vcpu_id);
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(vm, run->s.regs.gprs[reg]),
51		       sizeof(ucall));
52
53		vcpu_run_complete_io(vm, vcpu_id);
54		if (uc)
55			memcpy(uc, &ucall, sizeof(ucall));
56	}
57
58	return ucall.cmd;
59}
60