1 /*P:500 Just as userspace programs request kernel operations through a system
2 * call, the Guest requests Host operations through a "hypercall". You might
3 * notice this nomenclature doesn't really follow any logic, but the name has
4 * been around for long enough that we're stuck with it. As you'd expect, this
5 * code is basically a one big switch statement. :*/
6
7 /* Copyright (C) 2006 Rusty Russell IBM Corporation
8
9 This program is free software; you can redistribute it and/or modify
10 it under the terms of the GNU General Public License as published by
11 the Free Software Foundation; either version 2 of the License, or
12 (at your option) any later version.
13
14 This program is distributed in the hope that it will be useful,
15 but WITHOUT ANY WARRANTY; without even the implied warranty of
16 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17 GNU General Public License for more details.
18
19 You should have received a copy of the GNU General Public License
20 along with this program; if not, write to the Free Software
21 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
22 */
23 #include <linux/uaccess.h>
24 #include <linux/syscalls.h>
25 #include <linux/mm.h>
26 #include <linux/ktime.h>
27 #include <asm/page.h>
28 #include <asm/pgtable.h>
29 #include "lg.h"
30
31 /*H:120 This is the core hypercall routine: where the Guest gets what it wants.
32 * Or gets killed. Or, in the case of LHCALL_SHUTDOWN, both. */
do_hcall(struct lg_cpu * cpu,struct hcall_args * args)33 static void do_hcall(struct lg_cpu *cpu, struct hcall_args *args)
34 {
35 switch (args->arg0) {
36 case LHCALL_FLUSH_ASYNC:
37 /* This call does nothing, except by breaking out of the Guest
38 * it makes us process all the asynchronous hypercalls. */
39 break;
40 case LHCALL_LGUEST_INIT:
41 /* You can't get here unless you're already initialized. Don't
42 * do that. */
43 kill_guest(cpu, "already have lguest_data");
44 break;
45 case LHCALL_SHUTDOWN: {
46 /* Shutdown is such a trivial hypercall that we do it in four
47 * lines right here. */
48 char msg[128];
49 /* If the lgread fails, it will call kill_guest() itself; the
50 * kill_guest() with the message will be ignored. */
51 __lgread(cpu, msg, args->arg1, sizeof(msg));
52 msg[sizeof(msg)-1] = '\0';
53 kill_guest(cpu, "CRASH: %s", msg);
54 if (args->arg2 == LGUEST_SHUTDOWN_RESTART)
55 cpu->lg->dead = ERR_PTR(-ERESTART);
56 break;
57 }
58 case LHCALL_FLUSH_TLB:
59 /* FLUSH_TLB comes in two flavors, depending on the
60 * argument: */
61 if (args->arg1)
62 guest_pagetable_clear_all(cpu);
63 else
64 guest_pagetable_flush_user(cpu);
65 break;
66
67 /* All these calls simply pass the arguments through to the right
68 * routines. */
69 case LHCALL_NEW_PGTABLE:
70 guest_new_pagetable(cpu, args->arg1);
71 break;
72 case LHCALL_SET_STACK:
73 guest_set_stack(cpu, args->arg1, args->arg2, args->arg3);
74 break;
75 case LHCALL_SET_PTE:
76 guest_set_pte(cpu, args->arg1, args->arg2, __pte(args->arg3));
77 break;
78 case LHCALL_SET_PMD:
79 guest_set_pmd(cpu->lg, args->arg1, args->arg2);
80 break;
81 case LHCALL_SET_CLOCKEVENT:
82 guest_set_clockevent(cpu, args->arg1);
83 break;
84 case LHCALL_TS:
85 /* This sets the TS flag, as we saw used in run_guest(). */
86 cpu->ts = args->arg1;
87 break;
88 case LHCALL_HALT:
89 /* Similarly, this sets the halted flag for run_guest(). */
90 cpu->halted = 1;
91 break;
92 case LHCALL_NOTIFY:
93 cpu->pending_notify = args->arg1;
94 break;
95 default:
96 /* It should be an architecture-specific hypercall. */
97 if (lguest_arch_do_hcall(cpu, args))
98 kill_guest(cpu, "Bad hypercall %li\n", args->arg0);
99 }
100 }
101 /*:*/
102
103 /*H:124 Asynchronous hypercalls are easy: we just look in the array in the
104 * Guest's "struct lguest_data" to see if any new ones are marked "ready".
105 *
106 * We are careful to do these in order: obviously we respect the order the
107 * Guest put them in the ring, but we also promise the Guest that they will
108 * happen before any normal hypercall (which is why we check this before
109 * checking for a normal hcall). */
do_async_hcalls(struct lg_cpu * cpu)110 static void do_async_hcalls(struct lg_cpu *cpu)
111 {
112 unsigned int i;
113 u8 st[LHCALL_RING_SIZE];
114
115 /* For simplicity, we copy the entire call status array in at once. */
116 if (copy_from_user(&st, &cpu->lg->lguest_data->hcall_status, sizeof(st)))
117 return;
118
119 /* We process "struct lguest_data"s hcalls[] ring once. */
120 for (i = 0; i < ARRAY_SIZE(st); i++) {
121 struct hcall_args args;
122 /* We remember where we were up to from last time. This makes
123 * sure that the hypercalls are done in the order the Guest
124 * places them in the ring. */
125 unsigned int n = cpu->next_hcall;
126
127 /* 0xFF means there's no call here (yet). */
128 if (st[n] == 0xFF)
129 break;
130
131 /* OK, we have hypercall. Increment the "next_hcall" cursor,
132 * and wrap back to 0 if we reach the end. */
133 if (++cpu->next_hcall == LHCALL_RING_SIZE)
134 cpu->next_hcall = 0;
135
136 /* Copy the hypercall arguments into a local copy of
137 * the hcall_args struct. */
138 if (copy_from_user(&args, &cpu->lg->lguest_data->hcalls[n],
139 sizeof(struct hcall_args))) {
140 kill_guest(cpu, "Fetching async hypercalls");
141 break;
142 }
143
144 /* Do the hypercall, same as a normal one. */
145 do_hcall(cpu, &args);
146
147 /* Mark the hypercall done. */
148 if (put_user(0xFF, &cpu->lg->lguest_data->hcall_status[n])) {
149 kill_guest(cpu, "Writing result for async hypercall");
150 break;
151 }
152
153 /* Stop doing hypercalls if they want to notify the Launcher:
154 * it needs to service this first. */
155 if (cpu->pending_notify)
156 break;
157 }
158 }
159
160 /* Last of all, we look at what happens first of all. The very first time the
161 * Guest makes a hypercall, we end up here to set things up: */
initialize(struct lg_cpu * cpu)162 static void initialize(struct lg_cpu *cpu)
163 {
164 /* You can't do anything until you're initialized. The Guest knows the
165 * rules, so we're unforgiving here. */
166 if (cpu->hcall->arg0 != LHCALL_LGUEST_INIT) {
167 kill_guest(cpu, "hypercall %li before INIT", cpu->hcall->arg0);
168 return;
169 }
170
171 if (lguest_arch_init_hypercalls(cpu))
172 kill_guest(cpu, "bad guest page %p", cpu->lg->lguest_data);
173
174 /* The Guest tells us where we're not to deliver interrupts by putting
175 * the range of addresses into "struct lguest_data". */
176 if (get_user(cpu->lg->noirq_start, &cpu->lg->lguest_data->noirq_start)
177 || get_user(cpu->lg->noirq_end, &cpu->lg->lguest_data->noirq_end))
178 kill_guest(cpu, "bad guest page %p", cpu->lg->lguest_data);
179
180 /* We write the current time into the Guest's data page once so it can
181 * set its clock. */
182 write_timestamp(cpu);
183
184 /* page_tables.c will also do some setup. */
185 page_table_guest_data_init(cpu);
186
187 /* This is the one case where the above accesses might have been the
188 * first write to a Guest page. This may have caused a copy-on-write
189 * fault, but the old page might be (read-only) in the Guest
190 * pagetable. */
191 guest_pagetable_clear_all(cpu);
192 }
193 /*:*/
194
195 /*M:013 If a Guest reads from a page (so creates a mapping) that it has never
196 * written to, and then the Launcher writes to it (ie. the output of a virtual
197 * device), the Guest will still see the old page. In practice, this never
198 * happens: why would the Guest read a page which it has never written to? But
199 * a similar scenario might one day bite us, so it's worth mentioning. :*/
200
201 /*H:100
202 * Hypercalls
203 *
204 * Remember from the Guest, hypercalls come in two flavors: normal and
205 * asynchronous. This file handles both of types.
206 */
do_hypercalls(struct lg_cpu * cpu)207 void do_hypercalls(struct lg_cpu *cpu)
208 {
209 /* Not initialized yet? This hypercall must do it. */
210 if (unlikely(!cpu->lg->lguest_data)) {
211 /* Set up the "struct lguest_data" */
212 initialize(cpu);
213 /* Hcall is done. */
214 cpu->hcall = NULL;
215 return;
216 }
217
218 /* The Guest has initialized.
219 *
220 * Look in the hypercall ring for the async hypercalls: */
221 do_async_hcalls(cpu);
222
223 /* If we stopped reading the hypercall ring because the Guest did a
224 * NOTIFY to the Launcher, we want to return now. Otherwise we do
225 * the hypercall. */
226 if (!cpu->pending_notify) {
227 do_hcall(cpu, cpu->hcall);
228 /* Tricky point: we reset the hcall pointer to mark the
229 * hypercall as "done". We use the hcall pointer rather than
230 * the trap number to indicate a hypercall is pending.
231 * Normally it doesn't matter: the Guest will run again and
232 * update the trap number before we come back here.
233 *
234 * However, if we are signalled or the Guest sends I/O to the
235 * Launcher, the run_guest() loop will exit without running the
236 * Guest. When it comes back it would try to re-run the
237 * hypercall. Finding that bug sucked. */
238 cpu->hcall = NULL;
239 }
240 }
241
242 /* This routine supplies the Guest with time: it's used for wallclock time at
243 * initial boot and as a rough time source if the TSC isn't available. */
write_timestamp(struct lg_cpu * cpu)244 void write_timestamp(struct lg_cpu *cpu)
245 {
246 struct timespec now;
247 ktime_get_real_ts(&now);
248 if (copy_to_user(&cpu->lg->lguest_data->time,
249 &now, sizeof(struct timespec)))
250 kill_guest(cpu, "Writing timestamp");
251 }
252