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1/*P:500
2 * Just as userspace programs request kernel operations through a system
3 * call, the Guest requests Host operations through a "hypercall". You might
4 * notice this nomenclature doesn't really follow any logic, but the name has
5 * been around for long enough that we're stuck with it. As you'd expect, this
6 * code is basically a one big switch statement.
7:*/
8
9/* Copyright (C) 2006 Rusty Russell IBM Corporation
10
11 This program is free software; you can redistribute it and/or modify
12 it under the terms of the GNU General Public License as published by
13 the Free Software Foundation; either version 2 of the License, or
14 (at your option) any later version.
15
16 This program is distributed in the hope that it will be useful,
17 but WITHOUT ANY WARRANTY; without even the implied warranty of
18 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
19 GNU General Public License for more details.
20
21 You should have received a copy of the GNU General Public License
22 along with this program; if not, write to the Free Software
23 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
24*/
25#include <linux/uaccess.h>
26#include <linux/syscalls.h>
27#include <linux/mm.h>
28#include <linux/ktime.h>
29#include <asm/page.h>
30#include <asm/pgtable.h>
31#include "lg.h"
32
33/*H:120
34 * This is the core hypercall routine: where the Guest gets what it wants.
35 * Or gets killed. Or, in the case of LHCALL_SHUTDOWN, both.
36 */
37static void do_hcall(struct lg_cpu *cpu, struct hcall_args *args)
38{
39 switch (args->arg0) {
40 case LHCALL_FLUSH_ASYNC:
41 /*
42 * This call does nothing, except by breaking out of the Guest
43 * it makes us process all the asynchronous hypercalls.
44 */
45 break;
46 case LHCALL_SEND_INTERRUPTS:
47 /*
48 * This call does nothing too, but by breaking out of the Guest
49 * it makes us process any pending interrupts.
50 */
51 break;
52 case LHCALL_LGUEST_INIT:
53 /*
54 * You can't get here unless you're already initialized. Don't
55 * do that.
56 */
57 kill_guest(cpu, "already have lguest_data");
58 break;
59 case LHCALL_SHUTDOWN: {
60 char msg[128];
61 /*
62 * Shutdown is such a trivial hypercall that we do it in five
63 * lines right here.
64 *
65 * If the lgread fails, it will call kill_guest() itself; the
66 * kill_guest() with the message will be ignored.
67 */
68 __lgread(cpu, msg, args->arg1, sizeof(msg));
69 msg[sizeof(msg)-1] = '\0';
70 kill_guest(cpu, "CRASH: %s", msg);
71 if (args->arg2 == LGUEST_SHUTDOWN_RESTART)
72 cpu->lg->dead = ERR_PTR(-ERESTART);
73 break;
74 }
75 case LHCALL_FLUSH_TLB:
76 /* FLUSH_TLB comes in two flavors, depending on the argument: */
77 if (args->arg1)
78 guest_pagetable_clear_all(cpu);
79 else
80 guest_pagetable_flush_user(cpu);
81 break;
82
83 /*
84 * All these calls simply pass the arguments through to the right
85 * routines.
86 */
87 case LHCALL_NEW_PGTABLE:
88 guest_new_pagetable(cpu, args->arg1);
89 break;
90 case LHCALL_SET_STACK:
91 guest_set_stack(cpu, args->arg1, args->arg2, args->arg3);
92 break;
93 case LHCALL_SET_PTE:
94#ifdef CONFIG_X86_PAE
95 guest_set_pte(cpu, args->arg1, args->arg2,
96 __pte(args->arg3 | (u64)args->arg4 << 32));
97#else
98 guest_set_pte(cpu, args->arg1, args->arg2, __pte(args->arg3));
99#endif
100 break;
101 case LHCALL_SET_PGD:
102 guest_set_pgd(cpu->lg, args->arg1, args->arg2);
103 break;
104#ifdef CONFIG_X86_PAE
105 case LHCALL_SET_PMD:
106 guest_set_pmd(cpu->lg, args->arg1, args->arg2);
107 break;
108#endif
109 case LHCALL_SET_CLOCKEVENT:
110 guest_set_clockevent(cpu, args->arg1);
111 break;
112 case LHCALL_TS:
113 /* This sets the TS flag, as we saw used in run_guest(). */
114 cpu->ts = args->arg1;
115 break;
116 case LHCALL_HALT:
117 /* Similarly, this sets the halted flag for run_guest(). */
118 cpu->halted = 1;
119 break;
120 case LHCALL_NOTIFY:
121 cpu->pending_notify = args->arg1;
122 break;
123 default:
124 /* It should be an architecture-specific hypercall. */
125 if (lguest_arch_do_hcall(cpu, args))
126 kill_guest(cpu, "Bad hypercall %li\n", args->arg0);
127 }
128}
129
130/*H:124
131 * Asynchronous hypercalls are easy: we just look in the array in the
132 * Guest's "struct lguest_data" to see if any new ones are marked "ready".
133 *
134 * We are careful to do these in order: obviously we respect the order the
135 * Guest put them in the ring, but we also promise the Guest that they will
136 * happen before any normal hypercall (which is why we check this before
137 * checking for a normal hcall).
138 */
139static void do_async_hcalls(struct lg_cpu *cpu)
140{
141 unsigned int i;
142 u8 st[LHCALL_RING_SIZE];
143
144 /* For simplicity, we copy the entire call status array in at once. */
145 if (copy_from_user(&st, &cpu->lg->lguest_data->hcall_status, sizeof(st)))
146 return;
147
148 /* We process "struct lguest_data"s hcalls[] ring once. */
149 for (i = 0; i < ARRAY_SIZE(st); i++) {
150 struct hcall_args args;
151 /*
152 * We remember where we were up to from last time. This makes
153 * sure that the hypercalls are done in the order the Guest
154 * places them in the ring.
155 */
156 unsigned int n = cpu->next_hcall;
157
158 /* 0xFF means there's no call here (yet). */
159 if (st[n] == 0xFF)
160 break;
161
162 /*
163 * OK, we have hypercall. Increment the "next_hcall" cursor,
164 * and wrap back to 0 if we reach the end.
165 */
166 if (++cpu->next_hcall == LHCALL_RING_SIZE)
167 cpu->next_hcall = 0;
168
169 /*
170 * Copy the hypercall arguments into a local copy of the
171 * hcall_args struct.
172 */
173 if (copy_from_user(&args, &cpu->lg->lguest_data->hcalls[n],
174 sizeof(struct hcall_args))) {
175 kill_guest(cpu, "Fetching async hypercalls");
176 break;
177 }
178
179 /* Do the hypercall, same as a normal one. */
180 do_hcall(cpu, &args);
181
182 /* Mark the hypercall done. */
183 if (put_user(0xFF, &cpu->lg->lguest_data->hcall_status[n])) {
184 kill_guest(cpu, "Writing result for async hypercall");
185 break;
186 }
187
188 /*
189 * Stop doing hypercalls if they want to notify the Launcher:
190 * it needs to service this first.
191 */
192 if (cpu->pending_notify)
193 break;
194 }
195}
196
197/*
198 * Last of all, we look at what happens first of all. The very first time the
199 * Guest makes a hypercall, we end up here to set things up:
200 */
201static void initialize(struct lg_cpu *cpu)
202{
203 /*
204 * You can't do anything until you're initialized. The Guest knows the
205 * rules, so we're unforgiving here.
206 */
207 if (cpu->hcall->arg0 != LHCALL_LGUEST_INIT) {
208 kill_guest(cpu, "hypercall %li before INIT", cpu->hcall->arg0);
209 return;
210 }
211
212 if (lguest_arch_init_hypercalls(cpu))
213 kill_guest(cpu, "bad guest page %p", cpu->lg->lguest_data);
214
215 /*
216 * The Guest tells us where we're not to deliver interrupts by putting
217 * the range of addresses into "struct lguest_data".
218 */
219 if (get_user(cpu->lg->noirq_start, &cpu->lg->lguest_data->noirq_start)
220 || get_user(cpu->lg->noirq_end, &cpu->lg->lguest_data->noirq_end))
221 kill_guest(cpu, "bad guest page %p", cpu->lg->lguest_data);
222
223 /*
224 * We write the current time into the Guest's data page once so it can
225 * set its clock.
226 */
227 write_timestamp(cpu);
228
229 /* page_tables.c will also do some setup. */
230 page_table_guest_data_init(cpu);
231
232 /*
233 * This is the one case where the above accesses might have been the
234 * first write to a Guest page. This may have caused a copy-on-write
235 * fault, but the old page might be (read-only) in the Guest
236 * pagetable.
237 */
238 guest_pagetable_clear_all(cpu);
239}
240/*:*/
241
242/*M:013
243 * If a Guest reads from a page (so creates a mapping) that it has never
244 * written to, and then the Launcher writes to it (ie. the output of a virtual
245 * device), the Guest will still see the old page. In practice, this never
246 * happens: why would the Guest read a page which it has never written to? But
247 * a similar scenario might one day bite us, so it's worth mentioning.
248 *
249 * Note that if we used a shared anonymous mapping in the Launcher instead of
250 * mapping /dev/zero private, we wouldn't worry about cop-on-write. And we
251 * need that to switch the Launcher to processes (away from threads) anyway.
252:*/
253
254/*H:100
255 * Hypercalls
256 *
257 * Remember from the Guest, hypercalls come in two flavors: normal and
258 * asynchronous. This file handles both of types.
259 */
260void do_hypercalls(struct lg_cpu *cpu)
261{
262 /* Not initialized yet? This hypercall must do it. */
263 if (unlikely(!cpu->lg->lguest_data)) {
264 /* Set up the "struct lguest_data" */
265 initialize(cpu);
266 /* Hcall is done. */
267 cpu->hcall = NULL;
268 return;
269 }
270
271 /*
272 * The Guest has initialized.
273 *
274 * Look in the hypercall ring for the async hypercalls:
275 */
276 do_async_hcalls(cpu);
277
278 /*
279 * If we stopped reading the hypercall ring because the Guest did a
280 * NOTIFY to the Launcher, we want to return now. Otherwise we do
281 * the hypercall.
282 */
283 if (!cpu->pending_notify) {
284 do_hcall(cpu, cpu->hcall);
285 /*
286 * Tricky point: we reset the hcall pointer to mark the
287 * hypercall as "done". We use the hcall pointer rather than
288 * the trap number to indicate a hypercall is pending.
289 * Normally it doesn't matter: the Guest will run again and
290 * update the trap number before we come back here.
291 *
292 * However, if we are signalled or the Guest sends I/O to the
293 * Launcher, the run_guest() loop will exit without running the
294 * Guest. When it comes back it would try to re-run the
295 * hypercall. Finding that bug sucked.
296 */
297 cpu->hcall = NULL;
298 }
299}
300
301/*
302 * This routine supplies the Guest with time: it's used for wallclock time at
303 * initial boot and as a rough time source if the TSC isn't available.
304 */
305void write_timestamp(struct lg_cpu *cpu)
306{
307 struct timespec now;
308 ktime_get_real_ts(&now);
309 if (copy_to_user(&cpu->lg->lguest_data->time,
310 &now, sizeof(struct timespec)))
311 kill_guest(cpu, "Writing timestamp");
312}