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git.proxmox.com Git - mirror_ubuntu-artful-kernel.git/blob - drivers/lguest/hypercalls.c
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.
9 /* Copyright (C) 2006 Rusty Russell IBM Corporation
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.
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.
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
25 #include <linux/uaccess.h>
26 #include <linux/syscalls.h>
28 #include <linux/ktime.h>
30 #include <asm/pgtable.h>
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.
37 static void do_hcall(struct lg_cpu
*cpu
, struct hcall_args
*args
)
40 case LHCALL_FLUSH_ASYNC
:
42 * This call does nothing, except by breaking out of the Guest
43 * it makes us process all the asynchronous hypercalls.
46 case LHCALL_SEND_INTERRUPTS
:
48 * This call does nothing too, but by breaking out of the Guest
49 * it makes us process any pending interrupts.
52 case LHCALL_LGUEST_INIT
:
54 * You can't get here unless you're already initialized. Don't
57 kill_guest(cpu
, "already have lguest_data");
59 case LHCALL_SHUTDOWN
: {
62 * Shutdown is such a trivial hypercall that we do it in five
65 * If the lgread fails, it will call kill_guest() itself; the
66 * kill_guest() with the message will be ignored.
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
);
75 case LHCALL_FLUSH_TLB
:
76 /* FLUSH_TLB comes in two flavors, depending on the argument: */
78 guest_pagetable_clear_all(cpu
);
80 guest_pagetable_flush_user(cpu
);
84 * All these calls simply pass the arguments through to the right
87 case LHCALL_NEW_PGTABLE
:
88 guest_new_pagetable(cpu
, args
->arg1
);
90 case LHCALL_SET_STACK
:
91 guest_set_stack(cpu
, args
->arg1
, args
->arg2
, args
->arg3
);
95 guest_set_pte(cpu
, args
->arg1
, args
->arg2
,
96 __pte(args
->arg3
| (u64
)args
->arg4
<< 32));
98 guest_set_pte(cpu
, args
->arg1
, args
->arg2
, __pte(args
->arg3
));
102 guest_set_pgd(cpu
->lg
, args
->arg1
, args
->arg2
);
104 #ifdef CONFIG_X86_PAE
106 guest_set_pmd(cpu
->lg
, args
->arg1
, args
->arg2
);
109 case LHCALL_SET_CLOCKEVENT
:
110 guest_set_clockevent(cpu
, args
->arg1
);
113 /* This sets the TS flag, as we saw used in run_guest(). */
114 cpu
->ts
= args
->arg1
;
117 /* Similarly, this sets the halted flag for run_guest(). */
121 /* It should be an architecture-specific hypercall. */
122 if (lguest_arch_do_hcall(cpu
, args
))
123 kill_guest(cpu
, "Bad hypercall %li\n", args
->arg0
);
128 * Asynchronous hypercalls are easy: we just look in the array in the
129 * Guest's "struct lguest_data" to see if any new ones are marked "ready".
131 * We are careful to do these in order: obviously we respect the order the
132 * Guest put them in the ring, but we also promise the Guest that they will
133 * happen before any normal hypercall (which is why we check this before
134 * checking for a normal hcall).
136 static void do_async_hcalls(struct lg_cpu
*cpu
)
139 u8 st
[LHCALL_RING_SIZE
];
141 /* For simplicity, we copy the entire call status array in at once. */
142 if (copy_from_user(&st
, &cpu
->lg
->lguest_data
->hcall_status
, sizeof(st
)))
145 /* We process "struct lguest_data"s hcalls[] ring once. */
146 for (i
= 0; i
< ARRAY_SIZE(st
); i
++) {
147 struct hcall_args args
;
149 * We remember where we were up to from last time. This makes
150 * sure that the hypercalls are done in the order the Guest
151 * places them in the ring.
153 unsigned int n
= cpu
->next_hcall
;
155 /* 0xFF means there's no call here (yet). */
160 * OK, we have hypercall. Increment the "next_hcall" cursor,
161 * and wrap back to 0 if we reach the end.
163 if (++cpu
->next_hcall
== LHCALL_RING_SIZE
)
167 * Copy the hypercall arguments into a local copy of the
170 if (copy_from_user(&args
, &cpu
->lg
->lguest_data
->hcalls
[n
],
171 sizeof(struct hcall_args
))) {
172 kill_guest(cpu
, "Fetching async hypercalls");
176 /* Do the hypercall, same as a normal one. */
177 do_hcall(cpu
, &args
);
179 /* Mark the hypercall done. */
180 if (put_user(0xFF, &cpu
->lg
->lguest_data
->hcall_status
[n
])) {
181 kill_guest(cpu
, "Writing result for async hypercall");
186 * Stop doing hypercalls if they want to notify the Launcher:
187 * it needs to service this first.
189 if (cpu
->pending
.trap
)
195 * Last of all, we look at what happens first of all. The very first time the
196 * Guest makes a hypercall, we end up here to set things up:
198 static void initialize(struct lg_cpu
*cpu
)
201 * You can't do anything until you're initialized. The Guest knows the
202 * rules, so we're unforgiving here.
204 if (cpu
->hcall
->arg0
!= LHCALL_LGUEST_INIT
) {
205 kill_guest(cpu
, "hypercall %li before INIT", cpu
->hcall
->arg0
);
209 if (lguest_arch_init_hypercalls(cpu
))
210 kill_guest(cpu
, "bad guest page %p", cpu
->lg
->lguest_data
);
213 * The Guest tells us where we're not to deliver interrupts by putting
214 * the instruction address into "struct lguest_data".
216 if (get_user(cpu
->lg
->noirq_iret
, &cpu
->lg
->lguest_data
->noirq_iret
))
217 kill_guest(cpu
, "bad guest page %p", cpu
->lg
->lguest_data
);
220 * We write the current time into the Guest's data page once so it can
223 write_timestamp(cpu
);
225 /* page_tables.c will also do some setup. */
226 page_table_guest_data_init(cpu
);
229 * This is the one case where the above accesses might have been the
230 * first write to a Guest page. This may have caused a copy-on-write
231 * fault, but the old page might be (read-only) in the Guest
234 guest_pagetable_clear_all(cpu
);
239 * If a Guest reads from a page (so creates a mapping) that it has never
240 * written to, and then the Launcher writes to it (ie. the output of a virtual
241 * device), the Guest will still see the old page. In practice, this never
242 * happens: why would the Guest read a page which it has never written to? But
243 * a similar scenario might one day bite us, so it's worth mentioning.
245 * Note that if we used a shared anonymous mapping in the Launcher instead of
246 * mapping /dev/zero private, we wouldn't worry about cop-on-write. And we
247 * need that to switch the Launcher to processes (away from threads) anyway.
253 * Remember from the Guest, hypercalls come in two flavors: normal and
254 * asynchronous. This file handles both of types.
256 void do_hypercalls(struct lg_cpu
*cpu
)
258 /* Not initialized yet? This hypercall must do it. */
259 if (unlikely(!cpu
->lg
->lguest_data
)) {
260 /* Set up the "struct lguest_data" */
268 * The Guest has initialized.
270 * Look in the hypercall ring for the async hypercalls:
272 do_async_hcalls(cpu
);
275 * If we stopped reading the hypercall ring because the Guest did a
276 * NOTIFY to the Launcher, we want to return now. Otherwise we do
279 if (!cpu
->pending
.trap
) {
280 do_hcall(cpu
, cpu
->hcall
);
282 * Tricky point: we reset the hcall pointer to mark the
283 * hypercall as "done". We use the hcall pointer rather than
284 * the trap number to indicate a hypercall is pending.
285 * Normally it doesn't matter: the Guest will run again and
286 * update the trap number before we come back here.
288 * However, if we are signalled or the Guest sends I/O to the
289 * Launcher, the run_guest() loop will exit without running the
290 * Guest. When it comes back it would try to re-run the
291 * hypercall. Finding that bug sucked.
298 * This routine supplies the Guest with time: it's used for wallclock time at
299 * initial boot and as a rough time source if the TSC isn't available.
301 void write_timestamp(struct lg_cpu
*cpu
)
304 ktime_get_real_ts(&now
);
305 if (copy_to_user(&cpu
->lg
->lguest_data
->time
,
306 &now
, sizeof(struct timespec
)))
307 kill_guest(cpu
, "Writing timestamp");