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. :*/
7 /* Copyright (C) 2006 Rusty Russell IBM Corporation
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.
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.
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
23 #include <linux/uaccess.h>
24 #include <linux/syscalls.h>
27 #include <asm/pgtable.h>
28 #include <irq_vectors.h>
31 /*H:120 This is the core hypercall routine: where the Guest gets what it
32 * wants. Or gets killed. Or, in the case of LHCALL_CRASH, both.
34 * Remember from the Guest: %eax == which call to make, and the arguments are
35 * packed into %edx, %ebx and %ecx if needed. */
36 static void do_hcall(struct lguest *lg, struct lguest_regs *regs)
39 case LHCALL_FLUSH_ASYNC:
40 /* This call does nothing, except by breaking out of the Guest
41 * it makes us process all the asynchronous hypercalls. */
43 case LHCALL_LGUEST_INIT:
44 /* You can't get here unless you're already initialized. Don't
46 kill_guest(lg, "already have lguest_data");
49 /* Crash is such a trivial hypercall that we do it in four
50 * lines right here. */
52 /* If the lgread fails, it will call kill_guest() itself; the
53 * kill_guest() with the message will be ignored. */
54 lgread(lg, msg, regs->edx, sizeof(msg));
55 msg[sizeof(msg)-1] = '\0';
56 kill_guest(lg, "CRASH: %s", msg);
59 case LHCALL_FLUSH_TLB:
60 /* FLUSH_TLB comes in two flavors, depending on the
63 guest_pagetable_clear_all(lg);
65 guest_pagetable_flush_user(lg);
67 case LHCALL_GET_WALLCLOCK: {
68 /* The Guest wants to know the real time in seconds since 1970,
69 * in good Unix tradition. */
71 ktime_get_real_ts(&ts);
72 regs->eax = ts.tv_sec;
76 /* BIND_DMA really wants four arguments, but it's the only call
77 * which does. So the Guest packs the number of buffers and
78 * the interrupt number into the final argument, and we decode
79 * it here. This can legitimately fail, since we currently
80 * place a limit on the number of DMA pools a Guest can have.
81 * So we return true or false from this call. */
82 regs->eax = bind_dma(lg, regs->edx, regs->ebx,
83 regs->ecx >> 8, regs->ecx & 0xFF);
86 /* All these calls simply pass the arguments through to the right
89 send_dma(lg, regs->edx, regs->ebx);
92 load_guest_gdt(lg, regs->edx, regs->ebx);
94 case LHCALL_LOAD_IDT_ENTRY:
95 load_guest_idt_entry(lg, regs->edx, regs->ebx, regs->ecx);
97 case LHCALL_NEW_PGTABLE:
98 guest_new_pagetable(lg, regs->edx);
100 case LHCALL_SET_STACK:
101 guest_set_stack(lg, regs->edx, regs->ebx, regs->ecx);
104 guest_set_pte(lg, regs->edx, regs->ebx, mkgpte(regs->ecx));
107 guest_set_pmd(lg, regs->edx, regs->ebx);
109 case LHCALL_LOAD_TLS:
110 guest_load_tls(lg, regs->edx);
112 case LHCALL_SET_CLOCKEVENT:
113 guest_set_clockevent(lg, regs->edx);
117 /* This sets the TS flag, as we saw used in run_guest(). */
121 /* Similarly, this sets the halted flag for run_guest(). */
125 kill_guest(lg, "Bad hypercall %li\n", regs->eax);
129 /* Asynchronous hypercalls are easy: we just look in the array in the Guest's
130 * "struct lguest_data" and see if there are any new ones marked "ready".
132 * We are careful to do these in order: obviously we respect the order the
133 * Guest put them in the ring, but we also promise the Guest that they will
134 * happen before any normal hypercall (which is why we check this before
135 * checking for a normal hcall). */
136 static void do_async_hcalls(struct lguest *lg)
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, &lg->lguest_data->hcall_status, sizeof(st)))
146 /* We process "struct lguest_data"s hcalls[] ring once. */
147 for (i = 0; i < ARRAY_SIZE(st); i++) {
148 struct lguest_regs regs;
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. */
152 unsigned int n = lg->next_hcall;
154 /* 0xFF means there's no call here (yet). */
158 /* OK, we have hypercall. Increment the "next_hcall" cursor,
159 * and wrap back to 0 if we reach the end. */
160 if (++lg->next_hcall == LHCALL_RING_SIZE)
163 /* We copy the hypercall arguments into a fake register
164 * structure. This makes life simple for do_hcall(). */
165 if (get_user(regs.eax, &lg->lguest_data->hcalls[n].eax)
166 || get_user(regs.edx, &lg->lguest_data->hcalls[n].edx)
167 || get_user(regs.ecx, &lg->lguest_data->hcalls[n].ecx)
168 || get_user(regs.ebx, &lg->lguest_data->hcalls[n].ebx)) {
169 kill_guest(lg, "Fetching async hypercalls");
173 /* Do the hypercall, same as a normal one. */
176 /* Mark the hypercall done. */
177 if (put_user(0xFF, &lg->lguest_data->hcall_status[n])) {
178 kill_guest(lg, "Writing result for async hypercall");
182 /* Stop doing hypercalls if we've just done a DMA to the
183 * Launcher: it needs to service this first. */
184 if (lg->dma_is_pending)
189 /* Last of all, we look at what happens first of all. The very first time the
190 * Guest makes a hypercall, we end up here to set things up: */
191 static void initialize(struct lguest *lg)
195 /* You can't do anything until you're initialized. The Guest knows the
196 * rules, so we're unforgiving here. */
197 if (lg->regs->eax != LHCALL_LGUEST_INIT) {
198 kill_guest(lg, "hypercall %li before LGUEST_INIT",
203 /* We insist that the Time Stamp Counter exist and doesn't change with
204 * cpu frequency. Some devious chip manufacturers decided that TSC
205 * changes could be handled in software. I decided that time going
206 * backwards might be good for benchmarks, but it's bad for users.
208 * We also insist that the TSC be stable: the kernel detects unreliable
209 * TSCs for its own purposes, and we use that here. */
210 if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC) && !check_tsc_unstable())
215 /* The pointer to the Guest's "struct lguest_data" is the only
217 lg->lguest_data = (struct lguest_data __user *)lg->regs->edx;
218 /* If we check the address they gave is OK now, we can simply
219 * copy_to_user/from_user from now on rather than using lgread/lgwrite.
220 * I put this in to show that I'm not immune to writing stupid
222 if (!lguest_address_ok(lg, lg->regs->edx, sizeof(*lg->lguest_data))) {
223 kill_guest(lg, "bad guest page %p", lg->lguest_data);
226 /* The Guest tells us where we're not to deliver interrupts by putting
227 * the range of addresses into "struct lguest_data". */
228 if (get_user(lg->noirq_start, &lg->lguest_data->noirq_start)
229 || get_user(lg->noirq_end, &lg->lguest_data->noirq_end)
230 /* We tell the Guest that it can't use the top 4MB of virtual
231 * addresses used by the Switcher. */
232 || put_user(4U*1024*1024, &lg->lguest_data->reserve_mem)
233 || put_user(tsc_speed, &lg->lguest_data->tsc_khz)
234 /* We also give the Guest a unique id, as used in lguest_net.c. */
235 || put_user(lg->guestid, &lg->lguest_data->guestid))
236 kill_guest(lg, "bad guest page %p", lg->lguest_data);
238 /* This is the one case where the above accesses might have been the
239 * first write to a Guest page. This may have caused a copy-on-write
240 * fault, but the Guest might be referring to the old (read-only)
242 guest_pagetable_clear_all(lg);
244 /* Now we've examined the hypercall code; our Guest can make requests. There
245 * is one other way we can do things for the Guest, as we see in
248 /*H:110 Tricky point: we mark the hypercall as "done" once we've done it.
249 * Normally we don't need to do this: the Guest will run again and update the
250 * trap number before we come back around the run_guest() loop to
253 * However, if we are signalled or the Guest sends DMA to the Launcher, that
254 * loop will exit without running the Guest. When it comes back it would try
255 * to re-run the hypercall. */
256 static void clear_hcall(struct lguest *lg)
258 lg->regs->trapnum = 255;
264 * Remember from the Guest, hypercalls come in two flavors: normal and
265 * asynchronous. This file handles both of types.
267 void do_hypercalls(struct lguest *lg)
269 /* Not initialized yet? */
270 if (unlikely(!lg->lguest_data)) {
271 /* Did the Guest make a hypercall? We might have come back for
272 * some other reason (an interrupt, a different trap). */
273 if (lg->regs->trapnum == LGUEST_TRAP_ENTRY) {
274 /* Set up the "struct lguest_data" */
276 /* The hypercall is done. */
282 /* The Guest has initialized.
284 * Look in the hypercall ring for the async hypercalls: */
287 /* If we stopped reading the hypercall ring because the Guest did a
288 * SEND_DMA to the Launcher, we want to return now. Otherwise if the
289 * Guest asked us to do a hypercall, we do it. */
290 if (!lg->dma_is_pending && lg->regs->trapnum == LGUEST_TRAP_ENTRY) {
291 do_hcall(lg, lg->regs);
292 /* The hypercall is done. */