1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Copyright (C) 2012 - Virtual Open Systems and Columbia University
4 * Author: Christoffer Dall <c.dall@virtualopensystems.com>
5 */
6
7 #include <linux/kvm_host.h>
8 #include <asm/kvm_mmio.h>
9 #include <asm/kvm_emulate.h>
10 #include <trace/events/kvm.h>
11
12 #include "trace.h"
13
kvm_mmio_write_buf(void * buf,unsigned int len,unsigned long data)14 void kvm_mmio_write_buf(void *buf, unsigned int len, unsigned long data)
15 {
16 void *datap = NULL;
17 union {
18 u8 byte;
19 u16 hword;
20 u32 word;
21 u64 dword;
22 } tmp;
23
24 switch (len) {
25 case 1:
26 tmp.byte = data;
27 datap = &tmp.byte;
28 break;
29 case 2:
30 tmp.hword = data;
31 datap = &tmp.hword;
32 break;
33 case 4:
34 tmp.word = data;
35 datap = &tmp.word;
36 break;
37 case 8:
38 tmp.dword = data;
39 datap = &tmp.dword;
40 break;
41 }
42
43 memcpy(buf, datap, len);
44 }
45
kvm_mmio_read_buf(const void * buf,unsigned int len)46 unsigned long kvm_mmio_read_buf(const void *buf, unsigned int len)
47 {
48 unsigned long data = 0;
49 union {
50 u16 hword;
51 u32 word;
52 u64 dword;
53 } tmp;
54
55 switch (len) {
56 case 1:
57 data = *(u8 *)buf;
58 break;
59 case 2:
60 memcpy(&tmp.hword, buf, len);
61 data = tmp.hword;
62 break;
63 case 4:
64 memcpy(&tmp.word, buf, len);
65 data = tmp.word;
66 break;
67 case 8:
68 memcpy(&tmp.dword, buf, len);
69 data = tmp.dword;
70 break;
71 }
72
73 return data;
74 }
75
76 /**
77 * kvm_handle_mmio_return -- Handle MMIO loads after user space emulation
78 * or in-kernel IO emulation
79 *
80 * @vcpu: The VCPU pointer
81 * @run: The VCPU run struct containing the mmio data
82 */
kvm_handle_mmio_return(struct kvm_vcpu * vcpu,struct kvm_run * run)83 int kvm_handle_mmio_return(struct kvm_vcpu *vcpu, struct kvm_run *run)
84 {
85 unsigned long data;
86 unsigned int len;
87 int mask;
88
89 /* Detect an already handled MMIO return */
90 if (unlikely(!vcpu->mmio_needed))
91 return 0;
92
93 vcpu->mmio_needed = 0;
94
95 if (!run->mmio.is_write) {
96 len = run->mmio.len;
97 if (len > sizeof(unsigned long))
98 return -EINVAL;
99
100 data = kvm_mmio_read_buf(run->mmio.data, len);
101
102 if (vcpu->arch.mmio_decode.sign_extend &&
103 len < sizeof(unsigned long)) {
104 mask = 1U << ((len * 8) - 1);
105 data = (data ^ mask) - mask;
106 }
107
108 trace_kvm_mmio(KVM_TRACE_MMIO_READ, len, run->mmio.phys_addr,
109 &data);
110 data = vcpu_data_host_to_guest(vcpu, data, len);
111 vcpu_set_reg(vcpu, vcpu->arch.mmio_decode.rt, data);
112 }
113
114 /*
115 * The MMIO instruction is emulated and should not be re-executed
116 * in the guest.
117 */
118 kvm_skip_instr(vcpu, kvm_vcpu_trap_il_is32bit(vcpu));
119
120 return 0;
121 }
122
decode_hsr(struct kvm_vcpu * vcpu,bool * is_write,int * len)123 static int decode_hsr(struct kvm_vcpu *vcpu, bool *is_write, int *len)
124 {
125 unsigned long rt;
126 int access_size;
127 bool sign_extend;
128
129 if (kvm_vcpu_dabt_iss1tw(vcpu)) {
130 /* page table accesses IO mem: tell guest to fix its TTBR */
131 kvm_inject_dabt(vcpu, kvm_vcpu_get_hfar(vcpu));
132 return 1;
133 }
134
135 access_size = kvm_vcpu_dabt_get_as(vcpu);
136 if (unlikely(access_size < 0))
137 return access_size;
138
139 *is_write = kvm_vcpu_dabt_iswrite(vcpu);
140 sign_extend = kvm_vcpu_dabt_issext(vcpu);
141 rt = kvm_vcpu_dabt_get_rd(vcpu);
142
143 *len = access_size;
144 vcpu->arch.mmio_decode.sign_extend = sign_extend;
145 vcpu->arch.mmio_decode.rt = rt;
146
147 return 0;
148 }
149
io_mem_abort(struct kvm_vcpu * vcpu,struct kvm_run * run,phys_addr_t fault_ipa)150 int io_mem_abort(struct kvm_vcpu *vcpu, struct kvm_run *run,
151 phys_addr_t fault_ipa)
152 {
153 unsigned long data;
154 unsigned long rt;
155 int ret;
156 bool is_write;
157 int len;
158 u8 data_buf[8];
159
160 /*
161 * Prepare MMIO operation. First decode the syndrome data we get
162 * from the CPU. Then try if some in-kernel emulation feels
163 * responsible, otherwise let user space do its magic.
164 */
165 if (kvm_vcpu_dabt_isvalid(vcpu)) {
166 ret = decode_hsr(vcpu, &is_write, &len);
167 if (ret)
168 return ret;
169 } else {
170 kvm_err("load/store instruction decoding not implemented\n");
171 return -ENOSYS;
172 }
173
174 rt = vcpu->arch.mmio_decode.rt;
175
176 if (is_write) {
177 data = vcpu_data_guest_to_host(vcpu, vcpu_get_reg(vcpu, rt),
178 len);
179
180 trace_kvm_mmio(KVM_TRACE_MMIO_WRITE, len, fault_ipa, &data);
181 kvm_mmio_write_buf(data_buf, len, data);
182
183 ret = kvm_io_bus_write(vcpu, KVM_MMIO_BUS, fault_ipa, len,
184 data_buf);
185 } else {
186 trace_kvm_mmio(KVM_TRACE_MMIO_READ_UNSATISFIED, len,
187 fault_ipa, NULL);
188
189 ret = kvm_io_bus_read(vcpu, KVM_MMIO_BUS, fault_ipa, len,
190 data_buf);
191 }
192
193 /* Now prepare kvm_run for the potential return to userland. */
194 run->mmio.is_write = is_write;
195 run->mmio.phys_addr = fault_ipa;
196 run->mmio.len = len;
197 vcpu->mmio_needed = 1;
198
199 if (!ret) {
200 /* We handled the access successfully in the kernel. */
201 if (!is_write)
202 memcpy(run->mmio.data, data_buf, len);
203 vcpu->stat.mmio_exit_kernel++;
204 kvm_handle_mmio_return(vcpu, run);
205 return 1;
206 }
207
208 if (is_write)
209 memcpy(run->mmio.data, data_buf, len);
210 vcpu->stat.mmio_exit_user++;
211 run->exit_reason = KVM_EXIT_MMIO;
212 return 0;
213 }
214