1 // SPDX-License-Identifier: GPL-2.0-only
2 #include "kvm_util.h"
3 #include "linux/types.h"
4 #include "linux/bitmap.h"
5 #include "linux/atomic.h"
6 
7 #define GUEST_UCALL_FAILED -1
8 
9 struct ucall_header {
10 	DECLARE_BITMAP(in_use, KVM_MAX_VCPUS);
11 	struct ucall ucalls[KVM_MAX_VCPUS];
12 };
13 
14 int ucall_nr_pages_required(uint64_t page_size)
15 {
16 	return align_up(sizeof(struct ucall_header), page_size) / page_size;
17 }
18 
19 /*
20  * ucall_pool holds per-VM values (global data is duplicated by each VM), it
21  * must not be accessed from host code.
22  */
23 static struct ucall_header *ucall_pool;
24 
25 void ucall_init(struct kvm_vm *vm, vm_paddr_t mmio_gpa)
26 {
27 	struct ucall_header *hdr;
28 	struct ucall *uc;
29 	vm_vaddr_t vaddr;
30 	int i;
31 
32 	vaddr = __vm_vaddr_alloc(vm, sizeof(*hdr), KVM_UTIL_MIN_VADDR, MEM_REGION_DATA);
33 	hdr = (struct ucall_header *)addr_gva2hva(vm, vaddr);
34 	memset(hdr, 0, sizeof(*hdr));
35 
36 	for (i = 0; i < KVM_MAX_VCPUS; ++i) {
37 		uc = &hdr->ucalls[i];
38 		uc->hva = uc;
39 	}
40 
41 	write_guest_global(vm, ucall_pool, (struct ucall_header *)vaddr);
42 
43 	ucall_arch_init(vm, mmio_gpa);
44 }
45 
46 static struct ucall *ucall_alloc(void)
47 {
48 	struct ucall *uc;
49 	int i;
50 
51 	if (!ucall_pool)
52 		goto ucall_failed;
53 
54 	for (i = 0; i < KVM_MAX_VCPUS; ++i) {
55 		if (!test_and_set_bit(i, ucall_pool->in_use)) {
56 			uc = &ucall_pool->ucalls[i];
57 			memset(uc->args, 0, sizeof(uc->args));
58 			return uc;
59 		}
60 	}
61 
62 ucall_failed:
63 	/*
64 	 * If the vCPU cannot grab a ucall structure, make a bare ucall with a
65 	 * magic value to signal to get_ucall() that things went sideways.
66 	 * GUEST_ASSERT() depends on ucall_alloc() and so cannot be used here.
67 	 */
68 	ucall_arch_do_ucall(GUEST_UCALL_FAILED);
69 	return NULL;
70 }
71 
72 static void ucall_free(struct ucall *uc)
73 {
74 	/* Beware, here be pointer arithmetic.  */
75 	clear_bit(uc - ucall_pool->ucalls, ucall_pool->in_use);
76 }
77 
78 void ucall_assert(uint64_t cmd, const char *exp, const char *file,
79 		  unsigned int line, const char *fmt, ...)
80 {
81 	struct ucall *uc;
82 	va_list va;
83 
84 	uc = ucall_alloc();
85 	uc->cmd = cmd;
86 
87 	WRITE_ONCE(uc->args[GUEST_ERROR_STRING], (uint64_t)(exp));
88 	WRITE_ONCE(uc->args[GUEST_FILE], (uint64_t)(file));
89 	WRITE_ONCE(uc->args[GUEST_LINE], line);
90 
91 	va_start(va, fmt);
92 	guest_vsnprintf(uc->buffer, UCALL_BUFFER_LEN, fmt, va);
93 	va_end(va);
94 
95 	ucall_arch_do_ucall((vm_vaddr_t)uc->hva);
96 
97 	ucall_free(uc);
98 }
99 
100 void ucall_fmt(uint64_t cmd, const char *fmt, ...)
101 {
102 	struct ucall *uc;
103 	va_list va;
104 
105 	uc = ucall_alloc();
106 	uc->cmd = cmd;
107 
108 	va_start(va, fmt);
109 	guest_vsnprintf(uc->buffer, UCALL_BUFFER_LEN, fmt, va);
110 	va_end(va);
111 
112 	ucall_arch_do_ucall((vm_vaddr_t)uc->hva);
113 
114 	ucall_free(uc);
115 }
116 
117 void ucall(uint64_t cmd, int nargs, ...)
118 {
119 	struct ucall *uc;
120 	va_list va;
121 	int i;
122 
123 	uc = ucall_alloc();
124 
125 	WRITE_ONCE(uc->cmd, cmd);
126 
127 	nargs = min(nargs, UCALL_MAX_ARGS);
128 
129 	va_start(va, nargs);
130 	for (i = 0; i < nargs; ++i)
131 		WRITE_ONCE(uc->args[i], va_arg(va, uint64_t));
132 	va_end(va);
133 
134 	ucall_arch_do_ucall((vm_vaddr_t)uc->hva);
135 
136 	ucall_free(uc);
137 }
138 
139 uint64_t get_ucall(struct kvm_vcpu *vcpu, struct ucall *uc)
140 {
141 	struct ucall ucall;
142 	void *addr;
143 
144 	if (!uc)
145 		uc = &ucall;
146 
147 	addr = ucall_arch_get_ucall(vcpu);
148 	if (addr) {
149 		TEST_ASSERT(addr != (void *)GUEST_UCALL_FAILED,
150 			    "Guest failed to allocate ucall struct");
151 
152 		memcpy(uc, addr, sizeof(*uc));
153 		vcpu_run_complete_io(vcpu);
154 	} else {
155 		memset(uc, 0, sizeof(*uc));
156 	}
157 
158 	return uc->cmd;
159 }
160