blob: bf7942327bda5c2f122889e9881e1b7d90acaf44 [file] [log] [blame]
Jes Sorensen625efab2007-10-22 11:03:28 +10001/*
2 * Copyright (C) 2006, Rusty Russell <rusty@rustcorp.com.au> IBM Corporation.
3 * Copyright (C) 2007, Jes Sorensen <jes@sgi.com> SGI.
4 *
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License as published by
7 * the Free Software Foundation; either version 2 of the License, or
8 * (at your option) any later version.
9 *
10 * This program is distributed in the hope that it will be useful, but
11 * WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
13 * NON INFRINGEMENT. See the GNU General Public License for more
14 * details.
15 *
16 * You should have received a copy of the GNU General Public License
17 * along with this program; if not, write to the Free Software
18 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
19 */
Rusty Russella6bd8e12008-03-28 11:05:53 -050020/*P:450 This file contains the x86-specific lguest code. It used to be all
21 * mixed in with drivers/lguest/core.c but several foolhardy code slashers
22 * wrestled most of the dependencies out to here in preparation for porting
23 * lguest to other architectures (see what I mean by foolhardy?).
24 *
25 * This also contains a couple of non-obvious setup and teardown pieces which
26 * were implemented after days of debugging pain. :*/
Jes Sorensen625efab2007-10-22 11:03:28 +100027#include <linux/kernel.h>
28#include <linux/start_kernel.h>
29#include <linux/string.h>
30#include <linux/console.h>
31#include <linux/screen_info.h>
32#include <linux/irq.h>
33#include <linux/interrupt.h>
34#include <linux/clocksource.h>
35#include <linux/clockchips.h>
36#include <linux/cpu.h>
37#include <linux/lguest.h>
38#include <linux/lguest_launcher.h>
Jes Sorensen625efab2007-10-22 11:03:28 +100039#include <asm/paravirt.h>
40#include <asm/param.h>
41#include <asm/page.h>
42#include <asm/pgtable.h>
43#include <asm/desc.h>
44#include <asm/setup.h>
45#include <asm/lguest.h>
46#include <asm/uaccess.h>
47#include <asm/i387.h>
48#include "../lg.h"
49
50static int cpu_had_pge;
51
52static struct {
53 unsigned long offset;
54 unsigned short segment;
55} lguest_entry;
56
57/* Offset from where switcher.S was compiled to where we've copied it */
58static unsigned long switcher_offset(void)
59{
60 return SWITCHER_ADDR - (unsigned long)start_switcher_text;
61}
62
63/* This cpu's struct lguest_pages. */
64static struct lguest_pages *lguest_pages(unsigned int cpu)
65{
66 return &(((struct lguest_pages *)
67 (SWITCHER_ADDR + SHARED_SWITCHER_PAGES*PAGE_SIZE))[cpu]);
68}
69
Glauber de Oliveira Costac40a9f42008-01-17 19:11:20 -020070static DEFINE_PER_CPU(struct lg_cpu *, last_cpu);
Jes Sorensen625efab2007-10-22 11:03:28 +100071
72/*S:010
Rusty Russelle1e72962007-10-25 15:02:50 +100073 * We approach the Switcher.
Jes Sorensen625efab2007-10-22 11:03:28 +100074 *
75 * Remember that each CPU has two pages which are visible to the Guest when it
76 * runs on that CPU. This has to contain the state for that Guest: we copy the
77 * state in just before we run the Guest.
78 *
79 * Each Guest has "changed" flags which indicate what has changed in the Guest
80 * since it last ran. We saw this set in interrupts_and_traps.c and
81 * segments.c.
82 */
Glauber de Oliveira Costad0953d42008-01-07 11:05:25 -020083static void copy_in_guest_info(struct lg_cpu *cpu, struct lguest_pages *pages)
Jes Sorensen625efab2007-10-22 11:03:28 +100084{
85 /* Copying all this data can be quite expensive. We usually run the
86 * same Guest we ran last time (and that Guest hasn't run anywhere else
87 * meanwhile). If that's not the case, we pretend everything in the
88 * Guest has changed. */
Glauber de Oliveira Costaf34f8c52008-01-17 19:13:26 -020089 if (__get_cpu_var(last_cpu) != cpu || cpu->last_pages != pages) {
Glauber de Oliveira Costac40a9f42008-01-17 19:11:20 -020090 __get_cpu_var(last_cpu) = cpu;
Glauber de Oliveira Costaf34f8c52008-01-17 19:13:26 -020091 cpu->last_pages = pages;
Glauber de Oliveira Costaae3749d2008-01-17 19:14:46 -020092 cpu->changed = CHANGED_ALL;
Jes Sorensen625efab2007-10-22 11:03:28 +100093 }
94
95 /* These copies are pretty cheap, so we do them unconditionally: */
96 /* Save the current Host top-level page directory. */
97 pages->state.host_cr3 = __pa(current->mm->pgd);
98 /* Set up the Guest's page tables to see this CPU's pages (and no
99 * other CPU's pages). */
Glauber de Oliveira Costa0c784412008-01-07 11:05:30 -0200100 map_switcher_in_guest(cpu, pages);
Jes Sorensen625efab2007-10-22 11:03:28 +1000101 /* Set up the two "TSS" members which tell the CPU what stack to use
102 * for traps which do directly into the Guest (ie. traps at privilege
103 * level 1). */
Rusty Russelle95035c2008-01-31 18:00:47 +1100104 pages->state.guest_tss.sp1 = cpu->esp1;
Glauber de Oliveira Costa4665ac82008-01-07 11:05:35 -0200105 pages->state.guest_tss.ss1 = cpu->ss1;
Jes Sorensen625efab2007-10-22 11:03:28 +1000106
107 /* Copy direct-to-Guest trap entries. */
Glauber de Oliveira Costaae3749d2008-01-17 19:14:46 -0200108 if (cpu->changed & CHANGED_IDT)
Glauber de Oliveira Costafc708b32008-01-07 11:05:33 -0200109 copy_traps(cpu, pages->state.guest_idt, default_idt_entries);
Jes Sorensen625efab2007-10-22 11:03:28 +1000110
111 /* Copy all GDT entries which the Guest can change. */
Glauber de Oliveira Costaae3749d2008-01-17 19:14:46 -0200112 if (cpu->changed & CHANGED_GDT)
Glauber de Oliveira Costafc708b32008-01-07 11:05:33 -0200113 copy_gdt(cpu, pages->state.guest_gdt);
Jes Sorensen625efab2007-10-22 11:03:28 +1000114 /* If only the TLS entries have changed, copy them. */
Glauber de Oliveira Costaae3749d2008-01-17 19:14:46 -0200115 else if (cpu->changed & CHANGED_GDT_TLS)
Glauber de Oliveira Costafc708b32008-01-07 11:05:33 -0200116 copy_gdt_tls(cpu, pages->state.guest_gdt);
Jes Sorensen625efab2007-10-22 11:03:28 +1000117
118 /* Mark the Guest as unchanged for next time. */
Glauber de Oliveira Costaae3749d2008-01-17 19:14:46 -0200119 cpu->changed = 0;
Jes Sorensen625efab2007-10-22 11:03:28 +1000120}
121
122/* Finally: the code to actually call into the Switcher to run the Guest. */
Glauber de Oliveira Costad0953d42008-01-07 11:05:25 -0200123static void run_guest_once(struct lg_cpu *cpu, struct lguest_pages *pages)
Jes Sorensen625efab2007-10-22 11:03:28 +1000124{
125 /* This is a dummy value we need for GCC's sake. */
126 unsigned int clobber;
127
128 /* Copy the guest-specific information into this CPU's "struct
129 * lguest_pages". */
Glauber de Oliveira Costad0953d42008-01-07 11:05:25 -0200130 copy_in_guest_info(cpu, pages);
Jes Sorensen625efab2007-10-22 11:03:28 +1000131
132 /* Set the trap number to 256 (impossible value). If we fault while
133 * switching to the Guest (bad segment registers or bug), this will
134 * cause us to abort the Guest. */
Glauber de Oliveira Costaa53a35a2008-01-07 11:05:32 -0200135 cpu->regs->trapnum = 256;
Jes Sorensen625efab2007-10-22 11:03:28 +1000136
137 /* Now: we push the "eflags" register on the stack, then do an "lcall".
138 * This is how we change from using the kernel code segment to using
139 * the dedicated lguest code segment, as well as jumping into the
140 * Switcher.
141 *
142 * The lcall also pushes the old code segment (KERNEL_CS) onto the
143 * stack, then the address of this call. This stack layout happens to
Rusty Russelle1e72962007-10-25 15:02:50 +1000144 * exactly match the stack layout created by an interrupt... */
Jes Sorensen625efab2007-10-22 11:03:28 +1000145 asm volatile("pushf; lcall *lguest_entry"
146 /* This is how we tell GCC that %eax ("a") and %ebx ("b")
147 * are changed by this routine. The "=" means output. */
148 : "=a"(clobber), "=b"(clobber)
149 /* %eax contains the pages pointer. ("0" refers to the
150 * 0-th argument above, ie "a"). %ebx contains the
151 * physical address of the Guest's top-level page
152 * directory. */
Glauber de Oliveira Costa382ac6b2008-01-17 19:19:42 -0200153 : "0"(pages), "1"(__pa(cpu->lg->pgdirs[cpu->cpu_pgd].pgdir))
Jes Sorensen625efab2007-10-22 11:03:28 +1000154 /* We tell gcc that all these registers could change,
155 * which means we don't have to save and restore them in
156 * the Switcher. */
157 : "memory", "%edx", "%ecx", "%edi", "%esi");
158}
159/*:*/
160
Rusty Russelle1e72962007-10-25 15:02:50 +1000161/*M:002 There are hooks in the scheduler which we can register to tell when we
162 * get kicked off the CPU (preempt_notifier_register()). This would allow us
163 * to lazily disable SYSENTER which would regain some performance, and should
164 * also simplify copy_in_guest_info(). Note that we'd still need to restore
165 * things when we exit to Launcher userspace, but that's fairly easy.
166 *
Rusty Russella6bd8e12008-03-28 11:05:53 -0500167 * We could also try using this hooks for PGE, but that might be too expensive.
168 *
Rusty Russelle1e72962007-10-25 15:02:50 +1000169 * The hooks were designed for KVM, but we can also put them to good use. :*/
170
Jes Sorensen625efab2007-10-22 11:03:28 +1000171/*H:040 This is the i386-specific code to setup and run the Guest. Interrupts
172 * are disabled: we own the CPU. */
Glauber de Oliveira Costad0953d42008-01-07 11:05:25 -0200173void lguest_arch_run_guest(struct lg_cpu *cpu)
Jes Sorensen625efab2007-10-22 11:03:28 +1000174{
Rusty Russelle1e72962007-10-25 15:02:50 +1000175 /* Remember the awfully-named TS bit? If the Guest has asked to set it
176 * we set it now, so we can trap and pass that trap to the Guest if it
177 * uses the FPU. */
Glauber de Oliveira Costa4665ac82008-01-07 11:05:35 -0200178 if (cpu->ts)
Suresh Siddha54481cf82008-06-19 09:41:22 -0700179 unlazy_fpu(current);
Jes Sorensen625efab2007-10-22 11:03:28 +1000180
Rusty Russelle1e72962007-10-25 15:02:50 +1000181 /* SYSENTER is an optimized way of doing system calls. We can't allow
182 * it because it always jumps to privilege level 0. A normal Guest
183 * won't try it because we don't advertise it in CPUID, but a malicious
184 * Guest (or malicious Guest userspace program) could, so we tell the
185 * CPU to disable it before running the Guest. */
Jes Sorensen625efab2007-10-22 11:03:28 +1000186 if (boot_cpu_has(X86_FEATURE_SEP))
187 wrmsr(MSR_IA32_SYSENTER_CS, 0, 0);
188
Rusty Russelle1e72962007-10-25 15:02:50 +1000189 /* Now we actually run the Guest. It will return when something
190 * interesting happens, and we can examine its registers to see what it
191 * was doing. */
Glauber de Oliveira Costad0953d42008-01-07 11:05:25 -0200192 run_guest_once(cpu, lguest_pages(raw_smp_processor_id()));
Jes Sorensen625efab2007-10-22 11:03:28 +1000193
Rusty Russella6bd8e12008-03-28 11:05:53 -0500194 /* Note that the "regs" structure contains two extra entries which are
Rusty Russelle1e72962007-10-25 15:02:50 +1000195 * not really registers: a trap number which says what interrupt or
196 * trap made the switcher code come back, and an error code which some
197 * traps set. */
Jes Sorensen625efab2007-10-22 11:03:28 +1000198
Suresh Siddha54481cf82008-06-19 09:41:22 -0700199 /* Restore SYSENTER if it's supposed to be on. */
200 if (boot_cpu_has(X86_FEATURE_SEP))
201 wrmsr(MSR_IA32_SYSENTER_CS, __KERNEL_CS, 0);
202
Rusty Russelle1e72962007-10-25 15:02:50 +1000203 /* If the Guest page faulted, then the cr2 register will tell us the
204 * bad virtual address. We have to grab this now, because once we
205 * re-enable interrupts an interrupt could fault and thus overwrite
206 * cr2, or we could even move off to a different CPU. */
Glauber de Oliveira Costaa53a35a2008-01-07 11:05:32 -0200207 if (cpu->regs->trapnum == 14)
Glauber de Oliveira Costafc708b32008-01-07 11:05:33 -0200208 cpu->arch.last_pagefault = read_cr2();
Jes Sorensen625efab2007-10-22 11:03:28 +1000209 /* Similarly, if we took a trap because the Guest used the FPU,
Suresh Siddha54481cf82008-06-19 09:41:22 -0700210 * we have to restore the FPU it expects to see.
211 * math_state_restore() may sleep and we may even move off to
212 * a different CPU. So all the critical stuff should be done
213 * before this. */
Glauber de Oliveira Costaa53a35a2008-01-07 11:05:32 -0200214 else if (cpu->regs->trapnum == 7)
Jes Sorensen625efab2007-10-22 11:03:28 +1000215 math_state_restore();
Jes Sorensen625efab2007-10-22 11:03:28 +1000216}
217
Rusty Russelle1e72962007-10-25 15:02:50 +1000218/*H:130 Now we've examined the hypercall code; our Guest can make requests.
219 * Our Guest is usually so well behaved; it never tries to do things it isn't
220 * allowed to, and uses hypercalls instead. Unfortunately, Linux's paravirtual
221 * infrastructure isn't quite complete, because it doesn't contain replacements
222 * for the Intel I/O instructions. As a result, the Guest sometimes fumbles
223 * across one during the boot process as it probes for various things which are
224 * usually attached to a PC.
Jes Sorensen625efab2007-10-22 11:03:28 +1000225 *
Rusty Russelle1e72962007-10-25 15:02:50 +1000226 * When the Guest uses one of these instructions, we get a trap (General
Jes Sorensen625efab2007-10-22 11:03:28 +1000227 * Protection Fault) and come here. We see if it's one of those troublesome
228 * instructions and skip over it. We return true if we did. */
Glauber de Oliveira Costaa3863f62008-01-07 11:05:31 -0200229static int emulate_insn(struct lg_cpu *cpu)
Jes Sorensen625efab2007-10-22 11:03:28 +1000230{
231 u8 insn;
232 unsigned int insnlen = 0, in = 0, shift = 0;
233 /* The eip contains the *virtual* address of the Guest's instruction:
234 * guest_pa just subtracts the Guest's page_offset. */
Glauber de Oliveira Costa17136082008-01-07 11:05:37 -0200235 unsigned long physaddr = guest_pa(cpu, cpu->regs->eip);
Jes Sorensen625efab2007-10-22 11:03:28 +1000236
Rusty Russell47436aa2007-10-22 11:03:36 +1000237 /* This must be the Guest kernel trying to do something, not userspace!
238 * The bottom two bits of the CS segment register are the privilege
239 * level. */
Glauber de Oliveira Costaa53a35a2008-01-07 11:05:32 -0200240 if ((cpu->regs->cs & 3) != GUEST_PL)
Jes Sorensen625efab2007-10-22 11:03:28 +1000241 return 0;
242
243 /* Decoding x86 instructions is icky. */
Glauber de Oliveira Costa382ac6b2008-01-17 19:19:42 -0200244 insn = lgread(cpu, physaddr, u8);
Jes Sorensen625efab2007-10-22 11:03:28 +1000245
246 /* 0x66 is an "operand prefix". It means it's using the upper 16 bits
247 of the eax register. */
248 if (insn == 0x66) {
249 shift = 16;
250 /* The instruction is 1 byte so far, read the next byte. */
251 insnlen = 1;
Glauber de Oliveira Costa382ac6b2008-01-17 19:19:42 -0200252 insn = lgread(cpu, physaddr + insnlen, u8);
Jes Sorensen625efab2007-10-22 11:03:28 +1000253 }
254
255 /* We can ignore the lower bit for the moment and decode the 4 opcodes
256 * we need to emulate. */
257 switch (insn & 0xFE) {
258 case 0xE4: /* in <next byte>,%al */
259 insnlen += 2;
260 in = 1;
261 break;
262 case 0xEC: /* in (%dx),%al */
263 insnlen += 1;
264 in = 1;
265 break;
266 case 0xE6: /* out %al,<next byte> */
267 insnlen += 2;
268 break;
269 case 0xEE: /* out %al,(%dx) */
270 insnlen += 1;
271 break;
272 default:
273 /* OK, we don't know what this is, can't emulate. */
274 return 0;
275 }
276
277 /* If it was an "IN" instruction, they expect the result to be read
278 * into %eax, so we change %eax. We always return all-ones, which
279 * traditionally means "there's nothing there". */
280 if (in) {
281 /* Lower bit tells is whether it's a 16 or 32 bit access */
282 if (insn & 0x1)
Glauber de Oliveira Costaa53a35a2008-01-07 11:05:32 -0200283 cpu->regs->eax = 0xFFFFFFFF;
Jes Sorensen625efab2007-10-22 11:03:28 +1000284 else
Glauber de Oliveira Costaa53a35a2008-01-07 11:05:32 -0200285 cpu->regs->eax |= (0xFFFF << shift);
Jes Sorensen625efab2007-10-22 11:03:28 +1000286 }
287 /* Finally, we've "done" the instruction, so move past it. */
Glauber de Oliveira Costaa53a35a2008-01-07 11:05:32 -0200288 cpu->regs->eip += insnlen;
Jes Sorensen625efab2007-10-22 11:03:28 +1000289 /* Success! */
290 return 1;
291}
292
293/*H:050 Once we've re-enabled interrupts, we look at why the Guest exited. */
Glauber de Oliveira Costa73044f02008-01-07 11:05:27 -0200294void lguest_arch_handle_trap(struct lg_cpu *cpu)
Jes Sorensen625efab2007-10-22 11:03:28 +1000295{
Glauber de Oliveira Costaa53a35a2008-01-07 11:05:32 -0200296 switch (cpu->regs->trapnum) {
Rusty Russelle1e72962007-10-25 15:02:50 +1000297 case 13: /* We've intercepted a General Protection Fault. */
298 /* Check if this was one of those annoying IN or OUT
299 * instructions which we need to emulate. If so, we just go
300 * back into the Guest after we've done it. */
Glauber de Oliveira Costaa53a35a2008-01-07 11:05:32 -0200301 if (cpu->regs->errcode == 0) {
Glauber de Oliveira Costaa3863f62008-01-07 11:05:31 -0200302 if (emulate_insn(cpu))
Jes Sorensen625efab2007-10-22 11:03:28 +1000303 return;
304 }
305 break;
Rusty Russelle1e72962007-10-25 15:02:50 +1000306 case 14: /* We've intercepted a Page Fault. */
307 /* The Guest accessed a virtual address that wasn't mapped.
Rusty Russella6bd8e12008-03-28 11:05:53 -0500308 * This happens a lot: we don't actually set up most of the page
309 * tables for the Guest at all when we start: as it runs it asks
310 * for more and more, and we set them up as required. In this
311 * case, we don't even tell the Guest that the fault happened.
Rusty Russelle1e72962007-10-25 15:02:50 +1000312 *
313 * The errcode tells whether this was a read or a write, and
314 * whether kernel or userspace code. */
Glauber de Oliveira Costa17136082008-01-07 11:05:37 -0200315 if (demand_page(cpu, cpu->arch.last_pagefault,
316 cpu->regs->errcode))
Jes Sorensen625efab2007-10-22 11:03:28 +1000317 return;
318
Rusty Russelle1e72962007-10-25 15:02:50 +1000319 /* OK, it's really not there (or not OK): the Guest needs to
320 * know. We write out the cr2 value so it knows where the
321 * fault occurred.
322 *
323 * Note that if the Guest were really messed up, this could
324 * happen before it's done the LHCALL_LGUEST_INIT hypercall, so
325 * lg->lguest_data could be NULL */
Glauber de Oliveira Costa382ac6b2008-01-17 19:19:42 -0200326 if (cpu->lg->lguest_data &&
327 put_user(cpu->arch.last_pagefault,
328 &cpu->lg->lguest_data->cr2))
329 kill_guest(cpu, "Writing cr2");
Jes Sorensen625efab2007-10-22 11:03:28 +1000330 break;
331 case 7: /* We've intercepted a Device Not Available fault. */
Rusty Russelle1e72962007-10-25 15:02:50 +1000332 /* If the Guest doesn't want to know, we already restored the
333 * Floating Point Unit, so we just continue without telling
334 * it. */
Glauber de Oliveira Costa4665ac82008-01-07 11:05:35 -0200335 if (!cpu->ts)
Jes Sorensen625efab2007-10-22 11:03:28 +1000336 return;
337 break;
338 case 32 ... 255:
Rusty Russellcc6d4fb2007-10-22 11:03:30 +1000339 /* These values mean a real interrupt occurred, in which case
340 * the Host handler has already been run. We just do a
341 * friendly check if another process should now be run, then
342 * return to run the Guest again */
Jes Sorensen625efab2007-10-22 11:03:28 +1000343 cond_resched();
Rusty Russellcc6d4fb2007-10-22 11:03:30 +1000344 return;
345 case LGUEST_TRAP_ENTRY:
Jes Sorensenb410e7b2007-10-22 11:03:31 +1000346 /* Our 'struct hcall_args' maps directly over our regs: we set
347 * up the pointer now to indicate a hypercall is pending. */
Glauber de Oliveira Costaa53a35a2008-01-07 11:05:32 -0200348 cpu->hcall = (struct hcall_args *)cpu->regs;
Jes Sorensen625efab2007-10-22 11:03:28 +1000349 return;
350 }
351
352 /* We didn't handle the trap, so it needs to go to the Guest. */
Glauber de Oliveira Costaa53a35a2008-01-07 11:05:32 -0200353 if (!deliver_trap(cpu, cpu->regs->trapnum))
Jes Sorensen625efab2007-10-22 11:03:28 +1000354 /* If the Guest doesn't have a handler (either it hasn't
355 * registered any yet, or it's one of the faults we don't let
Rusty Russella6bd8e12008-03-28 11:05:53 -0500356 * it handle), it dies with this cryptic error message. */
Glauber de Oliveira Costa382ac6b2008-01-17 19:19:42 -0200357 kill_guest(cpu, "unhandled trap %li at %#lx (%#lx)",
Glauber de Oliveira Costaa53a35a2008-01-07 11:05:32 -0200358 cpu->regs->trapnum, cpu->regs->eip,
Glauber de Oliveira Costafc708b32008-01-07 11:05:33 -0200359 cpu->regs->trapnum == 14 ? cpu->arch.last_pagefault
Glauber de Oliveira Costaa53a35a2008-01-07 11:05:32 -0200360 : cpu->regs->errcode);
Jes Sorensen625efab2007-10-22 11:03:28 +1000361}
362
363/* Now we can look at each of the routines this calls, in increasing order of
364 * complexity: do_hypercalls(), emulate_insn(), maybe_do_interrupt(),
365 * deliver_trap() and demand_page(). After all those, we'll be ready to
366 * examine the Switcher, and our philosophical understanding of the Host/Guest
367 * duality will be complete. :*/
368static void adjust_pge(void *on)
369{
370 if (on)
371 write_cr4(read_cr4() | X86_CR4_PGE);
372 else
373 write_cr4(read_cr4() & ~X86_CR4_PGE);
374}
375
376/*H:020 Now the Switcher is mapped and every thing else is ready, we need to do
377 * some more i386-specific initialization. */
378void __init lguest_arch_host_init(void)
379{
380 int i;
381
382 /* Most of the i386/switcher.S doesn't care that it's been moved; on
383 * Intel, jumps are relative, and it doesn't access any references to
384 * external code or data.
385 *
386 * The only exception is the interrupt handlers in switcher.S: their
387 * addresses are placed in a table (default_idt_entries), so we need to
388 * update the table with the new addresses. switcher_offset() is a
Rusty Russella6bd8e12008-03-28 11:05:53 -0500389 * convenience function which returns the distance between the
390 * compiled-in switcher code and the high-mapped copy we just made. */
Jes Sorensen625efab2007-10-22 11:03:28 +1000391 for (i = 0; i < IDT_ENTRIES; i++)
392 default_idt_entries[i] += switcher_offset();
393
394 /*
395 * Set up the Switcher's per-cpu areas.
396 *
397 * Each CPU gets two pages of its own within the high-mapped region
398 * (aka. "struct lguest_pages"). Much of this can be initialized now,
399 * but some depends on what Guest we are running (which is set up in
400 * copy_in_guest_info()).
401 */
402 for_each_possible_cpu(i) {
403 /* lguest_pages() returns this CPU's two pages. */
404 struct lguest_pages *pages = lguest_pages(i);
405 /* This is a convenience pointer to make the code fit one
406 * statement to a line. */
407 struct lguest_ro_state *state = &pages->state;
408
409 /* The Global Descriptor Table: the Host has a different one
410 * for each CPU. We keep a descriptor for the GDT which says
411 * where it is and how big it is (the size is actually the last
412 * byte, not the size, hence the "-1"). */
413 state->host_gdt_desc.size = GDT_SIZE-1;
414 state->host_gdt_desc.address = (long)get_cpu_gdt_table(i);
415
416 /* All CPUs on the Host use the same Interrupt Descriptor
417 * Table, so we just use store_idt(), which gets this CPU's IDT
418 * descriptor. */
419 store_idt(&state->host_idt_desc);
420
421 /* The descriptors for the Guest's GDT and IDT can be filled
422 * out now, too. We copy the GDT & IDT into ->guest_gdt and
423 * ->guest_idt before actually running the Guest. */
424 state->guest_idt_desc.size = sizeof(state->guest_idt)-1;
425 state->guest_idt_desc.address = (long)&state->guest_idt;
426 state->guest_gdt_desc.size = sizeof(state->guest_gdt)-1;
427 state->guest_gdt_desc.address = (long)&state->guest_gdt;
428
429 /* We know where we want the stack to be when the Guest enters
Rusty Russella6bd8e12008-03-28 11:05:53 -0500430 * the Switcher: in pages->regs. The stack grows upwards, so
Jes Sorensen625efab2007-10-22 11:03:28 +1000431 * we start it at the end of that structure. */
H. Peter Anvinfaca6222008-01-30 13:31:02 +0100432 state->guest_tss.sp0 = (long)(&pages->regs + 1);
Jes Sorensen625efab2007-10-22 11:03:28 +1000433 /* And this is the GDT entry to use for the stack: we keep a
434 * couple of special LGUEST entries. */
435 state->guest_tss.ss0 = LGUEST_DS;
436
437 /* x86 can have a finegrained bitmap which indicates what I/O
438 * ports the process can use. We set it to the end of our
439 * structure, meaning "none". */
440 state->guest_tss.io_bitmap_base = sizeof(state->guest_tss);
441
442 /* Some GDT entries are the same across all Guests, so we can
443 * set them up now. */
444 setup_default_gdt_entries(state);
445 /* Most IDT entries are the same for all Guests, too.*/
446 setup_default_idt_entries(state, default_idt_entries);
447
448 /* The Host needs to be able to use the LGUEST segments on this
449 * CPU, too, so put them in the Host GDT. */
450 get_cpu_gdt_table(i)[GDT_ENTRY_LGUEST_CS] = FULL_EXEC_SEGMENT;
451 get_cpu_gdt_table(i)[GDT_ENTRY_LGUEST_DS] = FULL_SEGMENT;
452 }
453
454 /* In the Switcher, we want the %cs segment register to use the
455 * LGUEST_CS GDT entry: we've put that in the Host and Guest GDTs, so
456 * it will be undisturbed when we switch. To change %cs and jump we
457 * need this structure to feed to Intel's "lcall" instruction. */
458 lguest_entry.offset = (long)switch_to_guest + switcher_offset();
459 lguest_entry.segment = LGUEST_CS;
460
461 /* Finally, we need to turn off "Page Global Enable". PGE is an
462 * optimization where page table entries are specially marked to show
463 * they never change. The Host kernel marks all the kernel pages this
464 * way because it's always present, even when userspace is running.
465 *
466 * Lguest breaks this: unbeknownst to the rest of the Host kernel, we
467 * switch to the Guest kernel. If you don't disable this on all CPUs,
468 * you'll get really weird bugs that you'll chase for two days.
469 *
470 * I used to turn PGE off every time we switched to the Guest and back
471 * on when we return, but that slowed the Switcher down noticibly. */
472
473 /* We don't need the complexity of CPUs coming and going while we're
474 * doing this. */
Gautham R Shenoy86ef5c92008-01-25 21:08:02 +0100475 get_online_cpus();
Jes Sorensen625efab2007-10-22 11:03:28 +1000476 if (cpu_has_pge) { /* We have a broader idea of "global". */
477 /* Remember that this was originally set (for cleanup). */
478 cpu_had_pge = 1;
479 /* adjust_pge is a helper function which sets or unsets the PGE
480 * bit on its CPU, depending on the argument (0 == unset). */
Jens Axboe15c8b6c2008-05-09 09:39:44 +0200481 on_each_cpu(adjust_pge, (void *)0, 1);
Jes Sorensen625efab2007-10-22 11:03:28 +1000482 /* Turn off the feature in the global feature set. */
Andrew Mortoncf485e52008-06-09 16:22:48 -0700483 clear_cpu_cap(&boot_cpu_data, X86_FEATURE_PGE);
Jes Sorensen625efab2007-10-22 11:03:28 +1000484 }
Gautham R Shenoy86ef5c92008-01-25 21:08:02 +0100485 put_online_cpus();
Jes Sorensen625efab2007-10-22 11:03:28 +1000486};
487/*:*/
488
489void __exit lguest_arch_host_fini(void)
490{
491 /* If we had PGE before we started, turn it back on now. */
Gautham R Shenoy86ef5c92008-01-25 21:08:02 +0100492 get_online_cpus();
Jes Sorensen625efab2007-10-22 11:03:28 +1000493 if (cpu_had_pge) {
Andrew Mortoncf485e52008-06-09 16:22:48 -0700494 set_cpu_cap(&boot_cpu_data, X86_FEATURE_PGE);
Jes Sorensen625efab2007-10-22 11:03:28 +1000495 /* adjust_pge's argument "1" means set PGE. */
Jens Axboe15c8b6c2008-05-09 09:39:44 +0200496 on_each_cpu(adjust_pge, (void *)1, 1);
Jes Sorensen625efab2007-10-22 11:03:28 +1000497 }
Gautham R Shenoy86ef5c92008-01-25 21:08:02 +0100498 put_online_cpus();
Jes Sorensen625efab2007-10-22 11:03:28 +1000499}
Jes Sorensenb410e7b2007-10-22 11:03:31 +1000500
501
502/*H:122 The i386-specific hypercalls simply farm out to the right functions. */
Glauber de Oliveira Costa73044f02008-01-07 11:05:27 -0200503int lguest_arch_do_hcall(struct lg_cpu *cpu, struct hcall_args *args)
Jes Sorensenb410e7b2007-10-22 11:03:31 +1000504{
505 switch (args->arg0) {
506 case LHCALL_LOAD_GDT:
Glauber de Oliveira Costafc708b32008-01-07 11:05:33 -0200507 load_guest_gdt(cpu, args->arg1, args->arg2);
Jes Sorensenb410e7b2007-10-22 11:03:31 +1000508 break;
509 case LHCALL_LOAD_IDT_ENTRY:
Glauber de Oliveira Costafc708b32008-01-07 11:05:33 -0200510 load_guest_idt_entry(cpu, args->arg1, args->arg2, args->arg3);
Jes Sorensenb410e7b2007-10-22 11:03:31 +1000511 break;
512 case LHCALL_LOAD_TLS:
Glauber de Oliveira Costafc708b32008-01-07 11:05:33 -0200513 guest_load_tls(cpu, args->arg1);
Jes Sorensenb410e7b2007-10-22 11:03:31 +1000514 break;
515 default:
516 /* Bad Guest. Bad! */
517 return -EIO;
518 }
519 return 0;
520}
521
522/*H:126 i386-specific hypercall initialization: */
Glauber de Oliveira Costa73044f02008-01-07 11:05:27 -0200523int lguest_arch_init_hypercalls(struct lg_cpu *cpu)
Jes Sorensenb410e7b2007-10-22 11:03:31 +1000524{
525 u32 tsc_speed;
526
Rusty Russella6bd8e12008-03-28 11:05:53 -0500527 /* The pointer to the Guest's "struct lguest_data" is the only argument.
528 * We check that address now. */
Glauber de Oliveira Costa382ac6b2008-01-17 19:19:42 -0200529 if (!lguest_address_ok(cpu->lg, cpu->hcall->arg1,
530 sizeof(*cpu->lg->lguest_data)))
Jes Sorensenb410e7b2007-10-22 11:03:31 +1000531 return -EFAULT;
532
533 /* Having checked it, we simply set lg->lguest_data to point straight
534 * into the Launcher's memory at the right place and then use
535 * copy_to_user/from_user from now on, instead of lgread/write. I put
536 * this in to show that I'm not immune to writing stupid
537 * optimizations. */
Glauber de Oliveira Costa382ac6b2008-01-17 19:19:42 -0200538 cpu->lg->lguest_data = cpu->lg->mem_base + cpu->hcall->arg1;
Jes Sorensenb410e7b2007-10-22 11:03:31 +1000539
540 /* We insist that the Time Stamp Counter exist and doesn't change with
541 * cpu frequency. Some devious chip manufacturers decided that TSC
542 * changes could be handled in software. I decided that time going
543 * backwards might be good for benchmarks, but it's bad for users.
544 *
545 * We also insist that the TSC be stable: the kernel detects unreliable
546 * TSCs for its own purposes, and we use that here. */
547 if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC) && !check_tsc_unstable())
548 tsc_speed = tsc_khz;
549 else
550 tsc_speed = 0;
Glauber de Oliveira Costa382ac6b2008-01-17 19:19:42 -0200551 if (put_user(tsc_speed, &cpu->lg->lguest_data->tsc_khz))
Jes Sorensenb410e7b2007-10-22 11:03:31 +1000552 return -EFAULT;
553
Rusty Russellc18acd72007-10-22 11:03:35 +1000554 /* The interrupt code might not like the system call vector. */
Glauber de Oliveira Costa382ac6b2008-01-17 19:19:42 -0200555 if (!check_syscall_vector(cpu->lg))
556 kill_guest(cpu, "bad syscall vector");
Rusty Russellc18acd72007-10-22 11:03:35 +1000557
Jes Sorensenb410e7b2007-10-22 11:03:31 +1000558 return 0;
559}
Rusty Russella6bd8e12008-03-28 11:05:53 -0500560/*:*/
Jes Sorensend612cde2007-10-22 11:03:32 +1000561
562/*L:030 lguest_arch_setup_regs()
563 *
564 * Most of the Guest's registers are left alone: we used get_zeroed_page() to
565 * allocate the structure, so they will be 0. */
Glauber de Oliveira Costaa53a35a2008-01-07 11:05:32 -0200566void lguest_arch_setup_regs(struct lg_cpu *cpu, unsigned long start)
Jes Sorensend612cde2007-10-22 11:03:32 +1000567{
Glauber de Oliveira Costaa53a35a2008-01-07 11:05:32 -0200568 struct lguest_regs *regs = cpu->regs;
Jes Sorensend612cde2007-10-22 11:03:32 +1000569
570 /* There are four "segment" registers which the Guest needs to boot:
571 * The "code segment" register (cs) refers to the kernel code segment
572 * __KERNEL_CS, and the "data", "extra" and "stack" segment registers
573 * refer to the kernel data segment __KERNEL_DS.
574 *
575 * The privilege level is packed into the lower bits. The Guest runs
576 * at privilege level 1 (GUEST_PL).*/
577 regs->ds = regs->es = regs->ss = __KERNEL_DS|GUEST_PL;
578 regs->cs = __KERNEL_CS|GUEST_PL;
579
580 /* The "eflags" register contains miscellaneous flags. Bit 1 (0x002)
581 * is supposed to always be "1". Bit 9 (0x200) controls whether
582 * interrupts are enabled. We always leave interrupts enabled while
583 * running the Guest. */
Rusty Russell25c47bb2007-10-25 14:09:53 +1000584 regs->eflags = X86_EFLAGS_IF | 0x2;
Jes Sorensend612cde2007-10-22 11:03:32 +1000585
586 /* The "Extended Instruction Pointer" register says where the Guest is
587 * running. */
588 regs->eip = start;
589
590 /* %esi points to our boot information, at physical address 0, so don't
591 * touch it. */
Rusty Russelle1e72962007-10-25 15:02:50 +1000592
Jes Sorensend612cde2007-10-22 11:03:32 +1000593 /* There are a couple of GDT entries the Guest expects when first
594 * booting. */
Glauber de Oliveira Costafc708b32008-01-07 11:05:33 -0200595 setup_guest_gdt(cpu);
Jes Sorensend612cde2007-10-22 11:03:32 +1000596}