xref: /openbmc/linux/arch/x86/kernel/paravirt.c (revision 5c83511bdb9832c86be20fb86b783356e2f58062)
1 /*  Paravirtualization interfaces
2     Copyright (C) 2006 Rusty Russell IBM Corporation
3 
4     This program is free software; you can redistribute it and/or modify
5     it under the terms of the GNU General Public License as published by
6     the Free Software Foundation; either version 2 of the License, or
7     (at your option) any later version.
8 
9     This program is distributed in the hope that it will be useful,
10     but WITHOUT ANY WARRANTY; without even the implied warranty of
11     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
12     GNU General Public License for more details.
13 
14     You should have received a copy of the GNU General Public License
15     along with this program; if not, write to the Free Software
16     Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
17 
18     2007 - x86_64 support added by Glauber de Oliveira Costa, Red Hat Inc
19 */
20 
21 #include <linux/errno.h>
22 #include <linux/init.h>
23 #include <linux/export.h>
24 #include <linux/efi.h>
25 #include <linux/bcd.h>
26 #include <linux/highmem.h>
27 #include <linux/kprobes.h>
28 
29 #include <asm/bug.h>
30 #include <asm/paravirt.h>
31 #include <asm/debugreg.h>
32 #include <asm/desc.h>
33 #include <asm/setup.h>
34 #include <asm/pgtable.h>
35 #include <asm/time.h>
36 #include <asm/pgalloc.h>
37 #include <asm/irq.h>
38 #include <asm/delay.h>
39 #include <asm/fixmap.h>
40 #include <asm/apic.h>
41 #include <asm/tlbflush.h>
42 #include <asm/timer.h>
43 #include <asm/special_insns.h>
44 #include <asm/tlb.h>
45 
46 /*
47  * nop stub, which must not clobber anything *including the stack* to
48  * avoid confusing the entry prologues.
49  */
50 extern void _paravirt_nop(void);
51 asm (".pushsection .entry.text, \"ax\"\n"
52      ".global _paravirt_nop\n"
53      "_paravirt_nop:\n\t"
54      "ret\n\t"
55      ".size _paravirt_nop, . - _paravirt_nop\n\t"
56      ".type _paravirt_nop, @function\n\t"
57      ".popsection");
58 
59 /* identity function, which can be inlined */
60 u32 notrace _paravirt_ident_32(u32 x)
61 {
62 	return x;
63 }
64 
65 u64 notrace _paravirt_ident_64(u64 x)
66 {
67 	return x;
68 }
69 
70 void __init default_banner(void)
71 {
72 	printk(KERN_INFO "Booting paravirtualized kernel on %s\n",
73 	       pv_info.name);
74 }
75 
76 /* Undefined instruction for dealing with missing ops pointers. */
77 static const unsigned char ud2a[] = { 0x0f, 0x0b };
78 
79 struct branch {
80 	unsigned char opcode;
81 	u32 delta;
82 } __attribute__((packed));
83 
84 static unsigned paravirt_patch_call(void *insnbuf, const void *target,
85 				    unsigned long addr, unsigned len)
86 {
87 	struct branch *b = insnbuf;
88 	unsigned long delta = (unsigned long)target - (addr+5);
89 
90 	if (len < 5) {
91 #ifdef CONFIG_RETPOLINE
92 		WARN_ONCE("Failing to patch indirect CALL in %ps\n", (void *)addr);
93 #endif
94 		return len;	/* call too long for patch site */
95 	}
96 
97 	b->opcode = 0xe8; /* call */
98 	b->delta = delta;
99 	BUILD_BUG_ON(sizeof(*b) != 5);
100 
101 	return 5;
102 }
103 
104 static unsigned paravirt_patch_jmp(void *insnbuf, const void *target,
105 				   unsigned long addr, unsigned len)
106 {
107 	struct branch *b = insnbuf;
108 	unsigned long delta = (unsigned long)target - (addr+5);
109 
110 	if (len < 5) {
111 #ifdef CONFIG_RETPOLINE
112 		WARN_ONCE("Failing to patch indirect JMP in %ps\n", (void *)addr);
113 #endif
114 		return len;	/* call too long for patch site */
115 	}
116 
117 	b->opcode = 0xe9;	/* jmp */
118 	b->delta = delta;
119 
120 	return 5;
121 }
122 
123 DEFINE_STATIC_KEY_TRUE(virt_spin_lock_key);
124 
125 void __init native_pv_lock_init(void)
126 {
127 	if (!static_cpu_has(X86_FEATURE_HYPERVISOR))
128 		static_branch_disable(&virt_spin_lock_key);
129 }
130 
131 unsigned paravirt_patch_default(u8 type, void *insnbuf,
132 				unsigned long addr, unsigned len)
133 {
134 	/*
135 	 * Neat trick to map patch type back to the call within the
136 	 * corresponding structure.
137 	 */
138 	void *opfunc = *((void **)&pv_ops + type);
139 	unsigned ret;
140 
141 	if (opfunc == NULL)
142 		/* If there's no function, patch it with a ud2a (BUG) */
143 		ret = paravirt_patch_insns(insnbuf, len, ud2a, ud2a+sizeof(ud2a));
144 	else if (opfunc == _paravirt_nop)
145 		ret = 0;
146 
147 	/* identity functions just return their single argument */
148 	else if (opfunc == _paravirt_ident_32)
149 		ret = paravirt_patch_ident_32(insnbuf, len);
150 	else if (opfunc == _paravirt_ident_64)
151 		ret = paravirt_patch_ident_64(insnbuf, len);
152 
153 	else if (type == PARAVIRT_PATCH(cpu.iret) ||
154 		 type == PARAVIRT_PATCH(cpu.usergs_sysret64))
155 		/* If operation requires a jmp, then jmp */
156 		ret = paravirt_patch_jmp(insnbuf, opfunc, addr, len);
157 	else
158 		/* Otherwise call the function. */
159 		ret = paravirt_patch_call(insnbuf, opfunc, addr, len);
160 
161 	return ret;
162 }
163 
164 unsigned paravirt_patch_insns(void *insnbuf, unsigned len,
165 			      const char *start, const char *end)
166 {
167 	unsigned insn_len = end - start;
168 
169 	if (insn_len > len || start == NULL)
170 		insn_len = len;
171 	else
172 		memcpy(insnbuf, start, insn_len);
173 
174 	return insn_len;
175 }
176 
177 static void native_flush_tlb(void)
178 {
179 	__native_flush_tlb();
180 }
181 
182 /*
183  * Global pages have to be flushed a bit differently. Not a real
184  * performance problem because this does not happen often.
185  */
186 static void native_flush_tlb_global(void)
187 {
188 	__native_flush_tlb_global();
189 }
190 
191 static void native_flush_tlb_one_user(unsigned long addr)
192 {
193 	__native_flush_tlb_one_user(addr);
194 }
195 
196 struct static_key paravirt_steal_enabled;
197 struct static_key paravirt_steal_rq_enabled;
198 
199 static u64 native_steal_clock(int cpu)
200 {
201 	return 0;
202 }
203 
204 /* These are in entry.S */
205 extern void native_iret(void);
206 extern void native_usergs_sysret64(void);
207 
208 static struct resource reserve_ioports = {
209 	.start = 0,
210 	.end = IO_SPACE_LIMIT,
211 	.name = "paravirt-ioport",
212 	.flags = IORESOURCE_IO | IORESOURCE_BUSY,
213 };
214 
215 /*
216  * Reserve the whole legacy IO space to prevent any legacy drivers
217  * from wasting time probing for their hardware.  This is a fairly
218  * brute-force approach to disabling all non-virtual drivers.
219  *
220  * Note that this must be called very early to have any effect.
221  */
222 int paravirt_disable_iospace(void)
223 {
224 	return request_resource(&ioport_resource, &reserve_ioports);
225 }
226 
227 static DEFINE_PER_CPU(enum paravirt_lazy_mode, paravirt_lazy_mode) = PARAVIRT_LAZY_NONE;
228 
229 static inline void enter_lazy(enum paravirt_lazy_mode mode)
230 {
231 	BUG_ON(this_cpu_read(paravirt_lazy_mode) != PARAVIRT_LAZY_NONE);
232 
233 	this_cpu_write(paravirt_lazy_mode, mode);
234 }
235 
236 static void leave_lazy(enum paravirt_lazy_mode mode)
237 {
238 	BUG_ON(this_cpu_read(paravirt_lazy_mode) != mode);
239 
240 	this_cpu_write(paravirt_lazy_mode, PARAVIRT_LAZY_NONE);
241 }
242 
243 void paravirt_enter_lazy_mmu(void)
244 {
245 	enter_lazy(PARAVIRT_LAZY_MMU);
246 }
247 
248 void paravirt_leave_lazy_mmu(void)
249 {
250 	leave_lazy(PARAVIRT_LAZY_MMU);
251 }
252 
253 void paravirt_flush_lazy_mmu(void)
254 {
255 	preempt_disable();
256 
257 	if (paravirt_get_lazy_mode() == PARAVIRT_LAZY_MMU) {
258 		arch_leave_lazy_mmu_mode();
259 		arch_enter_lazy_mmu_mode();
260 	}
261 
262 	preempt_enable();
263 }
264 
265 void paravirt_start_context_switch(struct task_struct *prev)
266 {
267 	BUG_ON(preemptible());
268 
269 	if (this_cpu_read(paravirt_lazy_mode) == PARAVIRT_LAZY_MMU) {
270 		arch_leave_lazy_mmu_mode();
271 		set_ti_thread_flag(task_thread_info(prev), TIF_LAZY_MMU_UPDATES);
272 	}
273 	enter_lazy(PARAVIRT_LAZY_CPU);
274 }
275 
276 void paravirt_end_context_switch(struct task_struct *next)
277 {
278 	BUG_ON(preemptible());
279 
280 	leave_lazy(PARAVIRT_LAZY_CPU);
281 
282 	if (test_and_clear_ti_thread_flag(task_thread_info(next), TIF_LAZY_MMU_UPDATES))
283 		arch_enter_lazy_mmu_mode();
284 }
285 
286 enum paravirt_lazy_mode paravirt_get_lazy_mode(void)
287 {
288 	if (in_interrupt())
289 		return PARAVIRT_LAZY_NONE;
290 
291 	return this_cpu_read(paravirt_lazy_mode);
292 }
293 
294 struct pv_info pv_info = {
295 	.name = "bare hardware",
296 	.kernel_rpl = 0,
297 	.shared_kernel_pmd = 1,	/* Only used when CONFIG_X86_PAE is set */
298 
299 #ifdef CONFIG_X86_64
300 	.extra_user_64bit_cs = __USER_CS,
301 #endif
302 };
303 
304 #if defined(CONFIG_X86_32) && !defined(CONFIG_X86_PAE)
305 /* 32-bit pagetable entries */
306 #define PTE_IDENT	__PV_IS_CALLEE_SAVE(_paravirt_ident_32)
307 #else
308 /* 64-bit pagetable entries */
309 #define PTE_IDENT	__PV_IS_CALLEE_SAVE(_paravirt_ident_64)
310 #endif
311 
312 struct paravirt_patch_template pv_ops = {
313 	/* Init ops. */
314 	.init.patch		= native_patch,
315 
316 	/* Time ops. */
317 	.time.sched_clock	= native_sched_clock,
318 	.time.steal_clock	= native_steal_clock,
319 
320 	/* Cpu ops. */
321 	.cpu.cpuid		= native_cpuid,
322 	.cpu.get_debugreg	= native_get_debugreg,
323 	.cpu.set_debugreg	= native_set_debugreg,
324 	.cpu.read_cr0		= native_read_cr0,
325 	.cpu.write_cr0		= native_write_cr0,
326 	.cpu.write_cr4		= native_write_cr4,
327 #ifdef CONFIG_X86_64
328 	.cpu.read_cr8		= native_read_cr8,
329 	.cpu.write_cr8		= native_write_cr8,
330 #endif
331 	.cpu.wbinvd		= native_wbinvd,
332 	.cpu.read_msr		= native_read_msr,
333 	.cpu.write_msr		= native_write_msr,
334 	.cpu.read_msr_safe	= native_read_msr_safe,
335 	.cpu.write_msr_safe	= native_write_msr_safe,
336 	.cpu.read_pmc		= native_read_pmc,
337 	.cpu.load_tr_desc	= native_load_tr_desc,
338 	.cpu.set_ldt		= native_set_ldt,
339 	.cpu.load_gdt		= native_load_gdt,
340 	.cpu.load_idt		= native_load_idt,
341 	.cpu.store_tr		= native_store_tr,
342 	.cpu.load_tls		= native_load_tls,
343 #ifdef CONFIG_X86_64
344 	.cpu.load_gs_index	= native_load_gs_index,
345 #endif
346 	.cpu.write_ldt_entry	= native_write_ldt_entry,
347 	.cpu.write_gdt_entry	= native_write_gdt_entry,
348 	.cpu.write_idt_entry	= native_write_idt_entry,
349 
350 	.cpu.alloc_ldt		= paravirt_nop,
351 	.cpu.free_ldt		= paravirt_nop,
352 
353 	.cpu.load_sp0		= native_load_sp0,
354 
355 #ifdef CONFIG_X86_64
356 	.cpu.usergs_sysret64	= native_usergs_sysret64,
357 #endif
358 	.cpu.iret		= native_iret,
359 	.cpu.swapgs		= native_swapgs,
360 
361 	.cpu.set_iopl_mask	= native_set_iopl_mask,
362 	.cpu.io_delay		= native_io_delay,
363 
364 	.cpu.start_context_switch	= paravirt_nop,
365 	.cpu.end_context_switch		= paravirt_nop,
366 
367 	/* Irq ops. */
368 	.irq.save_fl		= __PV_IS_CALLEE_SAVE(native_save_fl),
369 	.irq.restore_fl		= __PV_IS_CALLEE_SAVE(native_restore_fl),
370 	.irq.irq_disable	= __PV_IS_CALLEE_SAVE(native_irq_disable),
371 	.irq.irq_enable		= __PV_IS_CALLEE_SAVE(native_irq_enable),
372 	.irq.safe_halt		= native_safe_halt,
373 	.irq.halt		= native_halt,
374 
375 	/* Mmu ops. */
376 	.mmu.read_cr2		= native_read_cr2,
377 	.mmu.write_cr2		= native_write_cr2,
378 	.mmu.read_cr3		= __native_read_cr3,
379 	.mmu.write_cr3		= native_write_cr3,
380 
381 	.mmu.flush_tlb_user	= native_flush_tlb,
382 	.mmu.flush_tlb_kernel	= native_flush_tlb_global,
383 	.mmu.flush_tlb_one_user	= native_flush_tlb_one_user,
384 	.mmu.flush_tlb_others	= native_flush_tlb_others,
385 	.mmu.tlb_remove_table	=
386 			(void (*)(struct mmu_gather *, void *))tlb_remove_page,
387 
388 	.mmu.pgd_alloc		= __paravirt_pgd_alloc,
389 	.mmu.pgd_free		= paravirt_nop,
390 
391 	.mmu.alloc_pte		= paravirt_nop,
392 	.mmu.alloc_pmd		= paravirt_nop,
393 	.mmu.alloc_pud		= paravirt_nop,
394 	.mmu.alloc_p4d		= paravirt_nop,
395 	.mmu.release_pte	= paravirt_nop,
396 	.mmu.release_pmd	= paravirt_nop,
397 	.mmu.release_pud	= paravirt_nop,
398 	.mmu.release_p4d	= paravirt_nop,
399 
400 	.mmu.set_pte		= native_set_pte,
401 	.mmu.set_pte_at		= native_set_pte_at,
402 	.mmu.set_pmd		= native_set_pmd,
403 
404 	.mmu.ptep_modify_prot_start	= __ptep_modify_prot_start,
405 	.mmu.ptep_modify_prot_commit	= __ptep_modify_prot_commit,
406 
407 #if CONFIG_PGTABLE_LEVELS >= 3
408 #ifdef CONFIG_X86_PAE
409 	.mmu.set_pte_atomic	= native_set_pte_atomic,
410 	.mmu.pte_clear		= native_pte_clear,
411 	.mmu.pmd_clear		= native_pmd_clear,
412 #endif
413 	.mmu.set_pud		= native_set_pud,
414 
415 	.mmu.pmd_val		= PTE_IDENT,
416 	.mmu.make_pmd		= PTE_IDENT,
417 
418 #if CONFIG_PGTABLE_LEVELS >= 4
419 	.mmu.pud_val		= PTE_IDENT,
420 	.mmu.make_pud		= PTE_IDENT,
421 
422 	.mmu.set_p4d		= native_set_p4d,
423 
424 #if CONFIG_PGTABLE_LEVELS >= 5
425 	.mmu.p4d_val		= PTE_IDENT,
426 	.mmu.make_p4d		= PTE_IDENT,
427 
428 	.mmu.set_pgd		= native_set_pgd,
429 #endif /* CONFIG_PGTABLE_LEVELS >= 5 */
430 #endif /* CONFIG_PGTABLE_LEVELS >= 4 */
431 #endif /* CONFIG_PGTABLE_LEVELS >= 3 */
432 
433 	.mmu.pte_val		= PTE_IDENT,
434 	.mmu.pgd_val		= PTE_IDENT,
435 
436 	.mmu.make_pte		= PTE_IDENT,
437 	.mmu.make_pgd		= PTE_IDENT,
438 
439 	.mmu.dup_mmap		= paravirt_nop,
440 	.mmu.exit_mmap		= paravirt_nop,
441 	.mmu.activate_mm	= paravirt_nop,
442 
443 	.mmu.lazy_mode = {
444 		.enter		= paravirt_nop,
445 		.leave		= paravirt_nop,
446 		.flush		= paravirt_nop,
447 	},
448 
449 	.mmu.set_fixmap		= native_set_fixmap,
450 
451 #if defined(CONFIG_PARAVIRT_SPINLOCKS)
452 	/* Lock ops. */
453 #ifdef CONFIG_SMP
454 	.lock.queued_spin_lock_slowpath	= native_queued_spin_lock_slowpath,
455 	.lock.queued_spin_unlock	=
456 				PV_CALLEE_SAVE(__native_queued_spin_unlock),
457 	.lock.wait			= paravirt_nop,
458 	.lock.kick			= paravirt_nop,
459 	.lock.vcpu_is_preempted		=
460 				PV_CALLEE_SAVE(__native_vcpu_is_preempted),
461 #endif /* SMP */
462 #endif
463 };
464 
465 /* At this point, native_get/set_debugreg has real function entries */
466 NOKPROBE_SYMBOL(native_get_debugreg);
467 NOKPROBE_SYMBOL(native_set_debugreg);
468 NOKPROBE_SYMBOL(native_load_idt);
469 
470 EXPORT_SYMBOL_GPL(pv_ops);
471 EXPORT_SYMBOL_GPL(pv_info);
472