root/arch/x86/kernel/paravirt.c

DEFINITIONS

1. default_banner
2. paravirt_patch_call
3. _paravirt_ident_64
4. paravirt_patch_jmp
5. native_pv_lock_init
6. paravirt_patch_default
7. paravirt_patch_insns
8. native_flush_tlb
9. native_flush_tlb_global
10. native_flush_tlb_one_user
11. native_steal_clock
12. paravirt_disable_iospace
13. enter_lazy
14. leave_lazy
15. paravirt_enter_lazy_mmu
16. paravirt_leave_lazy_mmu
17. paravirt_flush_lazy_mmu
18. paravirt_start_context_switch
19. paravirt_end_context_switch
20. paravirt_get_lazy_mode

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*  Paravirtualization interfaces
   3     Copyright (C) 2006 Rusty Russell IBM Corporation
   4 
   5 
   6     2007 - x86_64 support added by Glauber de Oliveira Costa, Red Hat Inc
   7 */
   8 
   9 #include <linux/errno.h>
  10 #include <linux/init.h>
  11 #include <linux/export.h>
  12 #include <linux/efi.h>
  13 #include <linux/bcd.h>
  14 #include <linux/highmem.h>
  15 #include <linux/kprobes.h>
  16 
  17 #include <asm/bug.h>
  18 #include <asm/paravirt.h>
  19 #include <asm/debugreg.h>
  20 #include <asm/desc.h>
  21 #include <asm/setup.h>
  22 #include <asm/pgtable.h>
  23 #include <asm/time.h>
  24 #include <asm/pgalloc.h>
  25 #include <asm/irq.h>
  26 #include <asm/delay.h>
  27 #include <asm/fixmap.h>
  28 #include <asm/apic.h>
  29 #include <asm/tlbflush.h>
  30 #include <asm/timer.h>
  31 #include <asm/special_insns.h>
  32 #include <asm/tlb.h>
  33 
  34 /*
  35  * nop stub, which must not clobber anything *including the stack* to
  36  * avoid confusing the entry prologues.
  37  */
  38 extern void _paravirt_nop(void);
  39 asm (".pushsection .entry.text, \"ax\"\n"
  40      ".global _paravirt_nop\n"
  41      "_paravirt_nop:\n\t"
  42      "ret\n\t"
  43      ".size _paravirt_nop, . - _paravirt_nop\n\t"
  44      ".type _paravirt_nop, @function\n\t"
  45      ".popsection");
  46 
  47 void __init default_banner(void)
  48 {
  49         printk(KERN_INFO "Booting paravirtualized kernel on %s\n",
  50                pv_info.name);
  51 }
  52 
  53 /* Undefined instruction for dealing with missing ops pointers. */
  54 static const unsigned char ud2a[] = { 0x0f, 0x0b };
  55 
  56 struct branch {
  57         unsigned char opcode;
  58         u32 delta;
  59 } __attribute__((packed));
  60 
  61 static unsigned paravirt_patch_call(void *insn_buff, const void *target,
  62                                     unsigned long addr, unsigned len)
  63 {
  64         const int call_len = 5;
  65         struct branch *b = insn_buff;
  66         unsigned long delta = (unsigned long)target - (addr+call_len);
  67 
  68         if (len < call_len) {
  69                 pr_warn("paravirt: Failed to patch indirect CALL at %ps\n", (void *)addr);
  70                 /* Kernel might not be viable if patching fails, bail out: */
  71                 BUG_ON(1);
  72         }
  73 
  74         b->opcode = 0xe8; /* call */
  75         b->delta = delta;
  76         BUILD_BUG_ON(sizeof(*b) != call_len);
  77 
  78         return call_len;
  79 }
  80 
  81 #ifdef CONFIG_PARAVIRT_XXL
  82 /* identity function, which can be inlined */
  83 u64 notrace _paravirt_ident_64(u64 x)
  84 {
  85         return x;
  86 }
  87 
  88 static unsigned paravirt_patch_jmp(void *insn_buff, const void *target,
  89                                    unsigned long addr, unsigned len)
  90 {
  91         struct branch *b = insn_buff;
  92         unsigned long delta = (unsigned long)target - (addr+5);
  93 
  94         if (len < 5) {
  95 #ifdef CONFIG_RETPOLINE
  96                 WARN_ONCE(1, "Failing to patch indirect JMP in %ps\n", (void *)addr);
  97 #endif
  98                 return len;     /* call too long for patch site */
  99         }
 100 
 101         b->opcode = 0xe9;       /* jmp */
 102         b->delta = delta;
 103 
 104         return 5;
 105 }
 106 #endif
 107 
 108 DEFINE_STATIC_KEY_TRUE(virt_spin_lock_key);
 109 
 110 void __init native_pv_lock_init(void)
 111 {
 112         if (!boot_cpu_has(X86_FEATURE_HYPERVISOR))
 113                 static_branch_disable(&virt_spin_lock_key);
 114 }
 115 
 116 unsigned paravirt_patch_default(u8 type, void *insn_buff,
 117                                 unsigned long addr, unsigned len)
 118 {
 119         /*
 120          * Neat trick to map patch type back to the call within the
 121          * corresponding structure.
 122          */
 123         void *opfunc = *((void **)&pv_ops + type);
 124         unsigned ret;
 125 
 126         if (opfunc == NULL)
 127                 /* If there's no function, patch it with a ud2a (BUG) */
 128                 ret = paravirt_patch_insns(insn_buff, len, ud2a, ud2a+sizeof(ud2a));
 129         else if (opfunc == _paravirt_nop)
 130                 ret = 0;
 131 
 132 #ifdef CONFIG_PARAVIRT_XXL
 133         /* identity functions just return their single argument */
 134         else if (opfunc == _paravirt_ident_64)
 135                 ret = paravirt_patch_ident_64(insn_buff, len);
 136 
 137         else if (type == PARAVIRT_PATCH(cpu.iret) ||
 138                  type == PARAVIRT_PATCH(cpu.usergs_sysret64))
 139                 /* If operation requires a jmp, then jmp */
 140                 ret = paravirt_patch_jmp(insn_buff, opfunc, addr, len);
 141 #endif
 142         else
 143                 /* Otherwise call the function. */
 144                 ret = paravirt_patch_call(insn_buff, opfunc, addr, len);
 145 
 146         return ret;
 147 }
 148 
 149 unsigned paravirt_patch_insns(void *insn_buff, unsigned len,
 150                               const char *start, const char *end)
 151 {
 152         unsigned insn_len = end - start;
 153 
 154         /* Alternative instruction is too large for the patch site and we cannot continue: */
 155         BUG_ON(insn_len > len || start == NULL);
 156 
 157         memcpy(insn_buff, start, insn_len);
 158 
 159         return insn_len;
 160 }
 161 
 162 static void native_flush_tlb(void)
 163 {
 164         __native_flush_tlb();
 165 }
 166 
 167 /*
 168  * Global pages have to be flushed a bit differently. Not a real
 169  * performance problem because this does not happen often.
 170  */
 171 static void native_flush_tlb_global(void)
 172 {
 173         __native_flush_tlb_global();
 174 }
 175 
 176 static void native_flush_tlb_one_user(unsigned long addr)
 177 {
 178         __native_flush_tlb_one_user(addr);
 179 }
 180 
 181 struct static_key paravirt_steal_enabled;
 182 struct static_key paravirt_steal_rq_enabled;
 183 
 184 static u64 native_steal_clock(int cpu)
 185 {
 186         return 0;
 187 }
 188 
 189 /* These are in entry.S */
 190 extern void native_iret(void);
 191 extern void native_usergs_sysret64(void);
 192 
 193 static struct resource reserve_ioports = {
 194         .start = 0,
 195         .end = IO_SPACE_LIMIT,
 196         .name = "paravirt-ioport",
 197         .flags = IORESOURCE_IO | IORESOURCE_BUSY,
 198 };
 199 
 200 /*
 201  * Reserve the whole legacy IO space to prevent any legacy drivers
 202  * from wasting time probing for their hardware.  This is a fairly
 203  * brute-force approach to disabling all non-virtual drivers.
 204  *
 205  * Note that this must be called very early to have any effect.
 206  */
 207 int paravirt_disable_iospace(void)
 208 {
 209         return request_resource(&ioport_resource, &reserve_ioports);
 210 }
 211 
 212 static DEFINE_PER_CPU(enum paravirt_lazy_mode, paravirt_lazy_mode) = PARAVIRT_LAZY_NONE;
 213 
 214 static inline void enter_lazy(enum paravirt_lazy_mode mode)
 215 {
 216         BUG_ON(this_cpu_read(paravirt_lazy_mode) != PARAVIRT_LAZY_NONE);
 217 
 218         this_cpu_write(paravirt_lazy_mode, mode);
 219 }
 220 
 221 static void leave_lazy(enum paravirt_lazy_mode mode)
 222 {
 223         BUG_ON(this_cpu_read(paravirt_lazy_mode) != mode);
 224 
 225         this_cpu_write(paravirt_lazy_mode, PARAVIRT_LAZY_NONE);
 226 }
 227 
 228 void paravirt_enter_lazy_mmu(void)
 229 {
 230         enter_lazy(PARAVIRT_LAZY_MMU);
 231 }
 232 
 233 void paravirt_leave_lazy_mmu(void)
 234 {
 235         leave_lazy(PARAVIRT_LAZY_MMU);
 236 }
 237 
 238 void paravirt_flush_lazy_mmu(void)
 239 {
 240         preempt_disable();
 241 
 242         if (paravirt_get_lazy_mode() == PARAVIRT_LAZY_MMU) {
 243                 arch_leave_lazy_mmu_mode();
 244                 arch_enter_lazy_mmu_mode();
 245         }
 246 
 247         preempt_enable();
 248 }
 249 
 250 #ifdef CONFIG_PARAVIRT_XXL
 251 void paravirt_start_context_switch(struct task_struct *prev)
 252 {
 253         BUG_ON(preemptible());
 254 
 255         if (this_cpu_read(paravirt_lazy_mode) == PARAVIRT_LAZY_MMU) {
 256                 arch_leave_lazy_mmu_mode();
 257                 set_ti_thread_flag(task_thread_info(prev), TIF_LAZY_MMU_UPDATES);
 258         }
 259         enter_lazy(PARAVIRT_LAZY_CPU);
 260 }
 261 
 262 void paravirt_end_context_switch(struct task_struct *next)
 263 {
 264         BUG_ON(preemptible());
 265 
 266         leave_lazy(PARAVIRT_LAZY_CPU);
 267 
 268         if (test_and_clear_ti_thread_flag(task_thread_info(next), TIF_LAZY_MMU_UPDATES))
 269                 arch_enter_lazy_mmu_mode();
 270 }
 271 #endif
 272 
 273 enum paravirt_lazy_mode paravirt_get_lazy_mode(void)
 274 {
 275         if (in_interrupt())
 276                 return PARAVIRT_LAZY_NONE;
 277 
 278         return this_cpu_read(paravirt_lazy_mode);
 279 }
 280 
 281 struct pv_info pv_info = {
 282         .name = "bare hardware",
 283 #ifdef CONFIG_PARAVIRT_XXL
 284         .kernel_rpl = 0,
 285         .shared_kernel_pmd = 1, /* Only used when CONFIG_X86_PAE is set */
 286 
 287 #ifdef CONFIG_X86_64
 288         .extra_user_64bit_cs = __USER_CS,
 289 #endif
 290 #endif
 291 };
 292 
 293 /* 64-bit pagetable entries */
 294 #define PTE_IDENT       __PV_IS_CALLEE_SAVE(_paravirt_ident_64)
 295 
 296 struct paravirt_patch_template pv_ops = {
 297         /* Init ops. */
 298         .init.patch             = native_patch,
 299 
 300         /* Time ops. */
 301         .time.sched_clock       = native_sched_clock,
 302         .time.steal_clock       = native_steal_clock,
 303 
 304         /* Cpu ops. */
 305         .cpu.io_delay           = native_io_delay,
 306 
 307 #ifdef CONFIG_PARAVIRT_XXL
 308         .cpu.cpuid              = native_cpuid,
 309         .cpu.get_debugreg       = native_get_debugreg,
 310         .cpu.set_debugreg       = native_set_debugreg,
 311         .cpu.read_cr0           = native_read_cr0,
 312         .cpu.write_cr0          = native_write_cr0,
 313         .cpu.write_cr4          = native_write_cr4,
 314         .cpu.wbinvd             = native_wbinvd,
 315         .cpu.read_msr           = native_read_msr,
 316         .cpu.write_msr          = native_write_msr,
 317         .cpu.read_msr_safe      = native_read_msr_safe,
 318         .cpu.write_msr_safe     = native_write_msr_safe,
 319         .cpu.read_pmc           = native_read_pmc,
 320         .cpu.load_tr_desc       = native_load_tr_desc,
 321         .cpu.set_ldt            = native_set_ldt,
 322         .cpu.load_gdt           = native_load_gdt,
 323         .cpu.load_idt           = native_load_idt,
 324         .cpu.store_tr           = native_store_tr,
 325         .cpu.load_tls           = native_load_tls,
 326 #ifdef CONFIG_X86_64
 327         .cpu.load_gs_index      = native_load_gs_index,
 328 #endif
 329         .cpu.write_ldt_entry    = native_write_ldt_entry,
 330         .cpu.write_gdt_entry    = native_write_gdt_entry,
 331         .cpu.write_idt_entry    = native_write_idt_entry,
 332 
 333         .cpu.alloc_ldt          = paravirt_nop,
 334         .cpu.free_ldt           = paravirt_nop,
 335 
 336         .cpu.load_sp0           = native_load_sp0,
 337 
 338 #ifdef CONFIG_X86_64
 339         .cpu.usergs_sysret64    = native_usergs_sysret64,
 340 #endif
 341         .cpu.iret               = native_iret,
 342         .cpu.swapgs             = native_swapgs,
 343 
 344         .cpu.set_iopl_mask      = native_set_iopl_mask,
 345 
 346         .cpu.start_context_switch       = paravirt_nop,
 347         .cpu.end_context_switch         = paravirt_nop,
 348 
 349         /* Irq ops. */
 350         .irq.save_fl            = __PV_IS_CALLEE_SAVE(native_save_fl),
 351         .irq.restore_fl         = __PV_IS_CALLEE_SAVE(native_restore_fl),
 352         .irq.irq_disable        = __PV_IS_CALLEE_SAVE(native_irq_disable),
 353         .irq.irq_enable         = __PV_IS_CALLEE_SAVE(native_irq_enable),
 354         .irq.safe_halt          = native_safe_halt,
 355         .irq.halt               = native_halt,
 356 #endif /* CONFIG_PARAVIRT_XXL */
 357 
 358         /* Mmu ops. */
 359         .mmu.flush_tlb_user     = native_flush_tlb,
 360         .mmu.flush_tlb_kernel   = native_flush_tlb_global,
 361         .mmu.flush_tlb_one_user = native_flush_tlb_one_user,
 362         .mmu.flush_tlb_others   = native_flush_tlb_others,
 363         .mmu.tlb_remove_table   =
 364                         (void (*)(struct mmu_gather *, void *))tlb_remove_page,
 365 
 366         .mmu.exit_mmap          = paravirt_nop,
 367 
 368 #ifdef CONFIG_PARAVIRT_XXL
 369         .mmu.read_cr2           = __PV_IS_CALLEE_SAVE(native_read_cr2),
 370         .mmu.write_cr2          = native_write_cr2,
 371         .mmu.read_cr3           = __native_read_cr3,
 372         .mmu.write_cr3          = native_write_cr3,
 373 
 374         .mmu.pgd_alloc          = __paravirt_pgd_alloc,
 375         .mmu.pgd_free           = paravirt_nop,
 376 
 377         .mmu.alloc_pte          = paravirt_nop,
 378         .mmu.alloc_pmd          = paravirt_nop,
 379         .mmu.alloc_pud          = paravirt_nop,
 380         .mmu.alloc_p4d          = paravirt_nop,
 381         .mmu.release_pte        = paravirt_nop,
 382         .mmu.release_pmd        = paravirt_nop,
 383         .mmu.release_pud        = paravirt_nop,
 384         .mmu.release_p4d        = paravirt_nop,
 385 
 386         .mmu.set_pte            = native_set_pte,
 387         .mmu.set_pte_at         = native_set_pte_at,
 388         .mmu.set_pmd            = native_set_pmd,
 389 
 390         .mmu.ptep_modify_prot_start     = __ptep_modify_prot_start,
 391         .mmu.ptep_modify_prot_commit    = __ptep_modify_prot_commit,
 392 
 393 #if CONFIG_PGTABLE_LEVELS >= 3
 394 #ifdef CONFIG_X86_PAE
 395         .mmu.set_pte_atomic     = native_set_pte_atomic,
 396         .mmu.pte_clear          = native_pte_clear,
 397         .mmu.pmd_clear          = native_pmd_clear,
 398 #endif
 399         .mmu.set_pud            = native_set_pud,
 400 
 401         .mmu.pmd_val            = PTE_IDENT,
 402         .mmu.make_pmd           = PTE_IDENT,
 403 
 404 #if CONFIG_PGTABLE_LEVELS >= 4
 405         .mmu.pud_val            = PTE_IDENT,
 406         .mmu.make_pud           = PTE_IDENT,
 407 
 408         .mmu.set_p4d            = native_set_p4d,
 409 
 410 #if CONFIG_PGTABLE_LEVELS >= 5
 411         .mmu.p4d_val            = PTE_IDENT,
 412         .mmu.make_p4d           = PTE_IDENT,
 413 
 414         .mmu.set_pgd            = native_set_pgd,
 415 #endif /* CONFIG_PGTABLE_LEVELS >= 5 */
 416 #endif /* CONFIG_PGTABLE_LEVELS >= 4 */
 417 #endif /* CONFIG_PGTABLE_LEVELS >= 3 */
 418 
 419         .mmu.pte_val            = PTE_IDENT,
 420         .mmu.pgd_val            = PTE_IDENT,
 421 
 422         .mmu.make_pte           = PTE_IDENT,
 423         .mmu.make_pgd           = PTE_IDENT,
 424 
 425         .mmu.dup_mmap           = paravirt_nop,
 426         .mmu.activate_mm        = paravirt_nop,
 427 
 428         .mmu.lazy_mode = {
 429                 .enter          = paravirt_nop,
 430                 .leave          = paravirt_nop,
 431                 .flush          = paravirt_nop,
 432         },
 433 
 434         .mmu.set_fixmap         = native_set_fixmap,
 435 #endif /* CONFIG_PARAVIRT_XXL */
 436 
 437 #if defined(CONFIG_PARAVIRT_SPINLOCKS)
 438         /* Lock ops. */
 439 #ifdef CONFIG_SMP
 440         .lock.queued_spin_lock_slowpath = native_queued_spin_lock_slowpath,
 441         .lock.queued_spin_unlock        =
 442                                 PV_CALLEE_SAVE(__native_queued_spin_unlock),
 443         .lock.wait                      = paravirt_nop,
 444         .lock.kick                      = paravirt_nop,
 445         .lock.vcpu_is_preempted         =
 446                                 PV_CALLEE_SAVE(__native_vcpu_is_preempted),
 447 #endif /* SMP */
 448 #endif
 449 };
 450 
 451 #ifdef CONFIG_PARAVIRT_XXL
 452 /* At this point, native_get/set_debugreg has real function entries */
 453 NOKPROBE_SYMBOL(native_get_debugreg);
 454 NOKPROBE_SYMBOL(native_set_debugreg);
 455 NOKPROBE_SYMBOL(native_load_idt);
 456 #endif
 457 
 458 EXPORT_SYMBOL(pv_ops);
 459 EXPORT_SYMBOL_GPL(pv_info);