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authorRusty Russell <rusty@rustcorp.com.au>2009-07-30 18:03:45 -0400
committerRusty Russell <rusty@rustcorp.com.au>2009-07-30 02:33:45 -0400
commit2e04ef76916d1e29a077ea9d0f2003c8fd86724d (patch)
tree2ff8d625d6e467be9f9f1b67a3674cb6e125e970 /drivers/lguest/hypercalls.c
parente969fed542cae08cb11d666efac4f7c5d624d09f (diff)
lguest: fix comment style
I don't really notice it (except to begrudge the extra vertical space), but Ingo does. And he pointed out that one excuse of lguest is as a teaching tool, it should set a good example. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Cc: Ingo Molnar <mingo@redhat.com>
Diffstat (limited to 'drivers/lguest/hypercalls.c')
-rw-r--r--drivers/lguest/hypercalls.c141
1 files changed, 92 insertions, 49 deletions
diff --git a/drivers/lguest/hypercalls.c b/drivers/lguest/hypercalls.c
index c29ffa19cb74..787ab4bc09f0 100644
--- a/drivers/lguest/hypercalls.c
+++ b/drivers/lguest/hypercalls.c
@@ -1,8 +1,10 @@
1/*P:500 Just as userspace programs request kernel operations through a system 1/*P:500
2 * Just as userspace programs request kernel operations through a system
2 * call, the Guest requests Host operations through a "hypercall". You might 3 * 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 * 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 * 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 * code is basically a one big switch statement.
7:*/
6 8
7/* Copyright (C) 2006 Rusty Russell IBM Corporation 9/* Copyright (C) 2006 Rusty Russell IBM Corporation
8 10
@@ -28,30 +30,41 @@
28#include <asm/pgtable.h> 30#include <asm/pgtable.h>
29#include "lg.h" 31#include "lg.h"
30 32
31/*H:120 This is the core hypercall routine: where the Guest gets what it wants. 33/*H:120
32 * Or gets killed. Or, in the case of LHCALL_SHUTDOWN, both. */ 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 */
33static void do_hcall(struct lg_cpu *cpu, struct hcall_args *args) 37static void do_hcall(struct lg_cpu *cpu, struct hcall_args *args)
34{ 38{
35 switch (args->arg0) { 39 switch (args->arg0) {
36 case LHCALL_FLUSH_ASYNC: 40 case LHCALL_FLUSH_ASYNC:
37 /* This call does nothing, except by breaking out of the Guest 41 /*
38 * it makes us process all the asynchronous hypercalls. */ 42 * This call does nothing, except by breaking out of the Guest
43 * it makes us process all the asynchronous hypercalls.
44 */
39 break; 45 break;
40 case LHCALL_SEND_INTERRUPTS: 46 case LHCALL_SEND_INTERRUPTS:
41 /* This call does nothing too, but by breaking out of the Guest 47 /*
42 * it makes us process any pending interrupts. */ 48 * This call does nothing too, but by breaking out of the Guest
49 * it makes us process any pending interrupts.
50 */
43 break; 51 break;
44 case LHCALL_LGUEST_INIT: 52 case LHCALL_LGUEST_INIT:
45 /* You can't get here unless you're already initialized. Don't 53 /*
46 * do that. */ 54 * You can't get here unless you're already initialized. Don't
55 * do that.
56 */
47 kill_guest(cpu, "already have lguest_data"); 57 kill_guest(cpu, "already have lguest_data");
48 break; 58 break;
49 case LHCALL_SHUTDOWN: { 59 case LHCALL_SHUTDOWN: {
50 /* Shutdown is such a trivial hypercall that we do it in four
51 * lines right here. */
52 char msg[128]; 60 char msg[128];
53 /* If the lgread fails, it will call kill_guest() itself; the 61 /*
54 * kill_guest() with the message will be ignored. */ 62 * Shutdown is such a trivial hypercall that we do it in four
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 */
55 __lgread(cpu, msg, args->arg1, sizeof(msg)); 68 __lgread(cpu, msg, args->arg1, sizeof(msg));
56 msg[sizeof(msg)-1] = '\0'; 69 msg[sizeof(msg)-1] = '\0';
57 kill_guest(cpu, "CRASH: %s", msg); 70 kill_guest(cpu, "CRASH: %s", msg);
@@ -60,16 +73,17 @@ static void do_hcall(struct lg_cpu *cpu, struct hcall_args *args)
60 break; 73 break;
61 } 74 }
62 case LHCALL_FLUSH_TLB: 75 case LHCALL_FLUSH_TLB:
63 /* FLUSH_TLB comes in two flavors, depending on the 76 /* FLUSH_TLB comes in two flavors, depending on the argument: */
64 * argument: */
65 if (args->arg1) 77 if (args->arg1)
66 guest_pagetable_clear_all(cpu); 78 guest_pagetable_clear_all(cpu);
67 else 79 else
68 guest_pagetable_flush_user(cpu); 80 guest_pagetable_flush_user(cpu);
69 break; 81 break;
70 82
71 /* All these calls simply pass the arguments through to the right 83 /*
72 * routines. */ 84 * All these calls simply pass the arguments through to the right
85 * routines.
86 */
73 case LHCALL_NEW_PGTABLE: 87 case LHCALL_NEW_PGTABLE:
74 guest_new_pagetable(cpu, args->arg1); 88 guest_new_pagetable(cpu, args->arg1);
75 break; 89 break;
@@ -112,15 +126,16 @@ static void do_hcall(struct lg_cpu *cpu, struct hcall_args *args)
112 kill_guest(cpu, "Bad hypercall %li\n", args->arg0); 126 kill_guest(cpu, "Bad hypercall %li\n", args->arg0);
113 } 127 }
114} 128}
115/*:*/
116 129
117/*H:124 Asynchronous hypercalls are easy: we just look in the array in the 130/*H:124
131 * Asynchronous hypercalls are easy: we just look in the array in the
118 * Guest's "struct lguest_data" to see if any new ones are marked "ready". 132 * Guest's "struct lguest_data" to see if any new ones are marked "ready".
119 * 133 *
120 * We are careful to do these in order: obviously we respect the order the 134 * We are careful to do these in order: obviously we respect the order the
121 * Guest put them in the ring, but we also promise the Guest that they will 135 * Guest put them in the ring, but we also promise the Guest that they will
122 * happen before any normal hypercall (which is why we check this before 136 * happen before any normal hypercall (which is why we check this before
123 * checking for a normal hcall). */ 137 * checking for a normal hcall).
138 */
124static void do_async_hcalls(struct lg_cpu *cpu) 139static void do_async_hcalls(struct lg_cpu *cpu)
125{ 140{
126 unsigned int i; 141 unsigned int i;
@@ -133,22 +148,28 @@ static void do_async_hcalls(struct lg_cpu *cpu)
133 /* We process "struct lguest_data"s hcalls[] ring once. */ 148 /* We process "struct lguest_data"s hcalls[] ring once. */
134 for (i = 0; i < ARRAY_SIZE(st); i++) { 149 for (i = 0; i < ARRAY_SIZE(st); i++) {
135 struct hcall_args args; 150 struct hcall_args args;
136 /* We remember where we were up to from last time. This makes 151 /*
152 * We remember where we were up to from last time. This makes
137 * sure that the hypercalls are done in the order the Guest 153 * sure that the hypercalls are done in the order the Guest
138 * places them in the ring. */ 154 * places them in the ring.
155 */
139 unsigned int n = cpu->next_hcall; 156 unsigned int n = cpu->next_hcall;
140 157
141 /* 0xFF means there's no call here (yet). */ 158 /* 0xFF means there's no call here (yet). */
142 if (st[n] == 0xFF) 159 if (st[n] == 0xFF)
143 break; 160 break;
144 161
145 /* OK, we have hypercall. Increment the "next_hcall" cursor, 162 /*
146 * and wrap back to 0 if we reach the end. */ 163 * OK, we have hypercall. Increment the "next_hcall" cursor,
164 * and wrap back to 0 if we reach the end.
165 */
147 if (++cpu->next_hcall == LHCALL_RING_SIZE) 166 if (++cpu->next_hcall == LHCALL_RING_SIZE)
148 cpu->next_hcall = 0; 167 cpu->next_hcall = 0;
149 168
150 /* Copy the hypercall arguments into a local copy of 169 /*
151 * the hcall_args struct. */ 170 * Copy the hypercall arguments into a local copy of the
171 * hcall_args struct.
172 */
152 if (copy_from_user(&args, &cpu->lg->lguest_data->hcalls[n], 173 if (copy_from_user(&args, &cpu->lg->lguest_data->hcalls[n],
153 sizeof(struct hcall_args))) { 174 sizeof(struct hcall_args))) {
154 kill_guest(cpu, "Fetching async hypercalls"); 175 kill_guest(cpu, "Fetching async hypercalls");
@@ -164,19 +185,25 @@ static void do_async_hcalls(struct lg_cpu *cpu)
164 break; 185 break;
165 } 186 }
166 187
167 /* Stop doing hypercalls if they want to notify the Launcher: 188 /*
168 * it needs to service this first. */ 189 * Stop doing hypercalls if they want to notify the Launcher:
190 * it needs to service this first.
191 */
169 if (cpu->pending_notify) 192 if (cpu->pending_notify)
170 break; 193 break;
171 } 194 }
172} 195}
173 196
174/* Last of all, we look at what happens first of all. The very first time the 197/*
175 * Guest makes a hypercall, we end up here to set things up: */ 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 */
176static void initialize(struct lg_cpu *cpu) 201static void initialize(struct lg_cpu *cpu)
177{ 202{
178 /* You can't do anything until you're initialized. The Guest knows the 203 /*
179 * rules, so we're unforgiving here. */ 204 * You can't do anything until you're initialized. The Guest knows the
205 * rules, so we're unforgiving here.
206 */
180 if (cpu->hcall->arg0 != LHCALL_LGUEST_INIT) { 207 if (cpu->hcall->arg0 != LHCALL_LGUEST_INIT) {
181 kill_guest(cpu, "hypercall %li before INIT", cpu->hcall->arg0); 208 kill_guest(cpu, "hypercall %li before INIT", cpu->hcall->arg0);
182 return; 209 return;
@@ -185,32 +212,40 @@ static void initialize(struct lg_cpu *cpu)
185 if (lguest_arch_init_hypercalls(cpu)) 212 if (lguest_arch_init_hypercalls(cpu))
186 kill_guest(cpu, "bad guest page %p", cpu->lg->lguest_data); 213 kill_guest(cpu, "bad guest page %p", cpu->lg->lguest_data);
187 214
188 /* The Guest tells us where we're not to deliver interrupts by putting 215 /*
189 * the range of addresses into "struct lguest_data". */ 216 * The Guest tells us where we're not to deliver interrupts by putting
217 * the range of addresses into "struct lguest_data".
218 */
190 if (get_user(cpu->lg->noirq_start, &cpu->lg->lguest_data->noirq_start) 219 if (get_user(cpu->lg->noirq_start, &cpu->lg->lguest_data->noirq_start)
191 || get_user(cpu->lg->noirq_end, &cpu->lg->lguest_data->noirq_end)) 220 || get_user(cpu->lg->noirq_end, &cpu->lg->lguest_data->noirq_end))
192 kill_guest(cpu, "bad guest page %p", cpu->lg->lguest_data); 221 kill_guest(cpu, "bad guest page %p", cpu->lg->lguest_data);
193 222
194 /* We write the current time into the Guest's data page once so it can 223 /*
195 * set its clock. */ 224 * We write the current time into the Guest's data page once so it can
225 * set its clock.
226 */
196 write_timestamp(cpu); 227 write_timestamp(cpu);
197 228
198 /* page_tables.c will also do some setup. */ 229 /* page_tables.c will also do some setup. */
199 page_table_guest_data_init(cpu); 230 page_table_guest_data_init(cpu);
200 231
201 /* This is the one case where the above accesses might have been the 232 /*
233 * This is the one case where the above accesses might have been the
202 * first write to a Guest page. This may have caused a copy-on-write 234 * first write to a Guest page. This may have caused a copy-on-write
203 * fault, but the old page might be (read-only) in the Guest 235 * fault, but the old page might be (read-only) in the Guest
204 * pagetable. */ 236 * pagetable.
237 */
205 guest_pagetable_clear_all(cpu); 238 guest_pagetable_clear_all(cpu);
206} 239}
207/*:*/ 240/*:*/
208 241
209/*M:013 If a Guest reads from a page (so creates a mapping) that it has never 242/*M:013
243 * If a Guest reads from a page (so creates a mapping) that it has never
210 * written to, and then the Launcher writes to it (ie. the output of a virtual 244 * written to, and then the Launcher writes to it (ie. the output of a virtual
211 * device), the Guest will still see the old page. In practice, this never 245 * device), the Guest will still see the old page. In practice, this never
212 * happens: why would the Guest read a page which it has never written to? But 246 * happens: why would the Guest read a page which it has never written to? But
213 * a similar scenario might one day bite us, so it's worth mentioning. :*/ 247 * a similar scenario might one day bite us, so it's worth mentioning.
248:*/
214 249
215/*H:100 250/*H:100
216 * Hypercalls 251 * Hypercalls
@@ -229,17 +264,22 @@ void do_hypercalls(struct lg_cpu *cpu)
229 return; 264 return;
230 } 265 }
231 266
232 /* The Guest has initialized. 267 /*
268 * The Guest has initialized.
233 * 269 *
234 * Look in the hypercall ring for the async hypercalls: */ 270 * Look in the hypercall ring for the async hypercalls:
271 */
235 do_async_hcalls(cpu); 272 do_async_hcalls(cpu);
236 273
237 /* If we stopped reading the hypercall ring because the Guest did a 274 /*
275 * If we stopped reading the hypercall ring because the Guest did a
238 * NOTIFY to the Launcher, we want to return now. Otherwise we do 276 * NOTIFY to the Launcher, we want to return now. Otherwise we do
239 * the hypercall. */ 277 * the hypercall.
278 */
240 if (!cpu->pending_notify) { 279 if (!cpu->pending_notify) {
241 do_hcall(cpu, cpu->hcall); 280 do_hcall(cpu, cpu->hcall);
242 /* Tricky point: we reset the hcall pointer to mark the 281 /*
282 * Tricky point: we reset the hcall pointer to mark the
243 * hypercall as "done". We use the hcall pointer rather than 283 * hypercall as "done". We use the hcall pointer rather than
244 * the trap number to indicate a hypercall is pending. 284 * the trap number to indicate a hypercall is pending.
245 * Normally it doesn't matter: the Guest will run again and 285 * Normally it doesn't matter: the Guest will run again and
@@ -248,13 +288,16 @@ void do_hypercalls(struct lg_cpu *cpu)
248 * However, if we are signalled or the Guest sends I/O to the 288 * However, if we are signalled or the Guest sends I/O to the
249 * Launcher, the run_guest() loop will exit without running the 289 * Launcher, the run_guest() loop will exit without running the
250 * Guest. When it comes back it would try to re-run the 290 * Guest. When it comes back it would try to re-run the
251 * hypercall. Finding that bug sucked. */ 291 * hypercall. Finding that bug sucked.
292 */
252 cpu->hcall = NULL; 293 cpu->hcall = NULL;
253 } 294 }
254} 295}
255 296
256/* This routine supplies the Guest with time: it's used for wallclock time at 297/*
257 * initial boot and as a rough time source if the TSC isn't available. */ 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.
300 */
258void write_timestamp(struct lg_cpu *cpu) 301void write_timestamp(struct lg_cpu *cpu)
259{ 302{
260 struct timespec now; 303 struct timespec now;