root/arch/mips/kvm/entry.c

DEFINITIONS

1. UASM_L_LA
2. kvm_mips_entry_setup
3. kvm_mips_build_save_scratch
4. kvm_mips_build_restore_scratch
5. build_set_exc_base
6. kvm_mips_build_vcpu_run
7. kvm_mips_build_enter_guest
8. kvm_mips_build_tlb_refill_exception
9. kvm_mips_build_exception
10. kvm_mips_build_exit
11. kvm_mips_build_ret_from_exit
12. kvm_mips_build_ret_to_guest
13. kvm_mips_build_ret_to_host

   1 /*
   2  * This file is subject to the terms and conditions of the GNU General Public
   3  * License.  See the file "COPYING" in the main directory of this archive
   4  * for more details.
   5  *
   6  * Generation of main entry point for the guest, exception handling.
   7  *
   8  * Copyright (C) 2012  MIPS Technologies, Inc.
   9  * Authors: Sanjay Lal <sanjayl@kymasys.com>
  10  *
  11  * Copyright (C) 2016 Imagination Technologies Ltd.
  12  */
  13 
  14 #include <linux/kvm_host.h>
  15 #include <linux/log2.h>
  16 #include <asm/mmu_context.h>
  17 #include <asm/msa.h>
  18 #include <asm/setup.h>
  19 #include <asm/tlbex.h>
  20 #include <asm/uasm.h>
  21 
  22 /* Register names */
  23 #define ZERO            0
  24 #define AT              1
  25 #define V0              2
  26 #define V1              3
  27 #define A0              4
  28 #define A1              5
  29 
  30 #if _MIPS_SIM == _MIPS_SIM_ABI32
  31 #define T0              8
  32 #define T1              9
  33 #define T2              10
  34 #define T3              11
  35 #endif /* _MIPS_SIM == _MIPS_SIM_ABI32 */
  36 
  37 #if _MIPS_SIM == _MIPS_SIM_ABI64 || _MIPS_SIM == _MIPS_SIM_NABI32
  38 #define T0              12
  39 #define T1              13
  40 #define T2              14
  41 #define T3              15
  42 #endif /* _MIPS_SIM == _MIPS_SIM_ABI64 || _MIPS_SIM == _MIPS_SIM_NABI32 */
  43 
  44 #define S0              16
  45 #define S1              17
  46 #define T9              25
  47 #define K0              26
  48 #define K1              27
  49 #define GP              28
  50 #define SP              29
  51 #define RA              31
  52 
  53 /* Some CP0 registers */
  54 #define C0_PWBASE       5, 5
  55 #define C0_HWRENA       7, 0
  56 #define C0_BADVADDR     8, 0
  57 #define C0_BADINSTR     8, 1
  58 #define C0_BADINSTRP    8, 2
  59 #define C0_ENTRYHI      10, 0
  60 #define C0_GUESTCTL1    10, 4
  61 #define C0_STATUS       12, 0
  62 #define C0_GUESTCTL0    12, 6
  63 #define C0_CAUSE        13, 0
  64 #define C0_EPC          14, 0
  65 #define C0_EBASE        15, 1
  66 #define C0_CONFIG5      16, 5
  67 #define C0_DDATA_LO     28, 3
  68 #define C0_ERROREPC     30, 0
  69 
  70 #define CALLFRAME_SIZ   32
  71 
  72 #ifdef CONFIG_64BIT
  73 #define ST0_KX_IF_64    ST0_KX
  74 #else
  75 #define ST0_KX_IF_64    0
  76 #endif
  77 
  78 static unsigned int scratch_vcpu[2] = { C0_DDATA_LO };
  79 static unsigned int scratch_tmp[2] = { C0_ERROREPC };
  80 
  81 enum label_id {
  82         label_fpu_1 = 1,
  83         label_msa_1,
  84         label_return_to_host,
  85         label_kernel_asid,
  86         label_exit_common,
  87 };
  88 
  89 UASM_L_LA(_fpu_1)
  90 UASM_L_LA(_msa_1)
  91 UASM_L_LA(_return_to_host)
  92 UASM_L_LA(_kernel_asid)
  93 UASM_L_LA(_exit_common)
  94 
  95 static void *kvm_mips_build_enter_guest(void *addr);
  96 static void *kvm_mips_build_ret_from_exit(void *addr);
  97 static void *kvm_mips_build_ret_to_guest(void *addr);
  98 static void *kvm_mips_build_ret_to_host(void *addr);
  99 
 100 /*
 101  * The version of this function in tlbex.c uses current_cpu_type(), but for KVM
 102  * we assume symmetry.
 103  */
 104 static int c0_kscratch(void)
 105 {
 106         switch (boot_cpu_type()) {
 107         case CPU_XLP:
 108         case CPU_XLR:
 109                 return 22;
 110         default:
 111                 return 31;
 112         }
 113 }
 114 
 115 /**
 116  * kvm_mips_entry_setup() - Perform global setup for entry code.
 117  *
 118  * Perform global setup for entry code, such as choosing a scratch register.
 119  *
 120  * Returns:     0 on success.
 121  *              -errno on failure.
 122  */
 123 int kvm_mips_entry_setup(void)
 124 {
 125         /*
 126          * We prefer to use KScratchN registers if they are available over the
 127          * defaults above, which may not work on all cores.
 128          */
 129         unsigned int kscratch_mask = cpu_data[0].kscratch_mask;
 130 
 131         if (pgd_reg != -1)
 132                 kscratch_mask &= ~BIT(pgd_reg);
 133 
 134         /* Pick a scratch register for storing VCPU */
 135         if (kscratch_mask) {
 136                 scratch_vcpu[0] = c0_kscratch();
 137                 scratch_vcpu[1] = ffs(kscratch_mask) - 1;
 138                 kscratch_mask &= ~BIT(scratch_vcpu[1]);
 139         }
 140 
 141         /* Pick a scratch register to use as a temp for saving state */
 142         if (kscratch_mask) {
 143                 scratch_tmp[0] = c0_kscratch();
 144                 scratch_tmp[1] = ffs(kscratch_mask) - 1;
 145                 kscratch_mask &= ~BIT(scratch_tmp[1]);
 146         }
 147 
 148         return 0;
 149 }
 150 
 151 static void kvm_mips_build_save_scratch(u32 **p, unsigned int tmp,
 152                                         unsigned int frame)
 153 {
 154         /* Save the VCPU scratch register value in cp0_epc of the stack frame */
 155         UASM_i_MFC0(p, tmp, scratch_vcpu[0], scratch_vcpu[1]);
 156         UASM_i_SW(p, tmp, offsetof(struct pt_regs, cp0_epc), frame);
 157 
 158         /* Save the temp scratch register value in cp0_cause of stack frame */
 159         if (scratch_tmp[0] == c0_kscratch()) {
 160                 UASM_i_MFC0(p, tmp, scratch_tmp[0], scratch_tmp[1]);
 161                 UASM_i_SW(p, tmp, offsetof(struct pt_regs, cp0_cause), frame);
 162         }
 163 }
 164 
 165 static void kvm_mips_build_restore_scratch(u32 **p, unsigned int tmp,
 166                                            unsigned int frame)
 167 {
 168         /*
 169          * Restore host scratch register values saved by
 170          * kvm_mips_build_save_scratch().
 171          */
 172         UASM_i_LW(p, tmp, offsetof(struct pt_regs, cp0_epc), frame);
 173         UASM_i_MTC0(p, tmp, scratch_vcpu[0], scratch_vcpu[1]);
 174 
 175         if (scratch_tmp[0] == c0_kscratch()) {
 176                 UASM_i_LW(p, tmp, offsetof(struct pt_regs, cp0_cause), frame);
 177                 UASM_i_MTC0(p, tmp, scratch_tmp[0], scratch_tmp[1]);
 178         }
 179 }
 180 
 181 /**
 182  * build_set_exc_base() - Assemble code to write exception base address.
 183  * @p:          Code buffer pointer.
 184  * @reg:        Source register (generated code may set WG bit in @reg).
 185  *
 186  * Assemble code to modify the exception base address in the EBase register,
 187  * using the appropriately sized access and setting the WG bit if necessary.
 188  */
 189 static inline void build_set_exc_base(u32 **p, unsigned int reg)
 190 {
 191         if (cpu_has_ebase_wg) {
 192                 /* Set WG so that all the bits get written */
 193                 uasm_i_ori(p, reg, reg, MIPS_EBASE_WG);
 194                 UASM_i_MTC0(p, reg, C0_EBASE);
 195         } else {
 196                 uasm_i_mtc0(p, reg, C0_EBASE);
 197         }
 198 }
 199 
 200 /**
 201  * kvm_mips_build_vcpu_run() - Assemble function to start running a guest VCPU.
 202  * @addr:       Address to start writing code.
 203  *
 204  * Assemble the start of the vcpu_run function to run a guest VCPU. The function
 205  * conforms to the following prototype:
 206  *
 207  * int vcpu_run(struct kvm_run *run, struct kvm_vcpu *vcpu);
 208  *
 209  * The exit from the guest and return to the caller is handled by the code
 210  * generated by kvm_mips_build_ret_to_host().
 211  *
 212  * Returns:     Next address after end of written function.
 213  */
 214 void *kvm_mips_build_vcpu_run(void *addr)
 215 {
 216         u32 *p = addr;
 217         unsigned int i;
 218 
 219         /*
 220          * A0: run
 221          * A1: vcpu
 222          */
 223 
 224         /* k0/k1 not being used in host kernel context */
 225         UASM_i_ADDIU(&p, K1, SP, -(int)sizeof(struct pt_regs));
 226         for (i = 16; i < 32; ++i) {
 227                 if (i == 24)
 228                         i = 28;
 229                 UASM_i_SW(&p, i, offsetof(struct pt_regs, regs[i]), K1);
 230         }
 231 
 232         /* Save host status */
 233         uasm_i_mfc0(&p, V0, C0_STATUS);
 234         UASM_i_SW(&p, V0, offsetof(struct pt_regs, cp0_status), K1);
 235 
 236         /* Save scratch registers, will be used to store pointer to vcpu etc */
 237         kvm_mips_build_save_scratch(&p, V1, K1);
 238 
 239         /* VCPU scratch register has pointer to vcpu */
 240         UASM_i_MTC0(&p, A1, scratch_vcpu[0], scratch_vcpu[1]);
 241 
 242         /* Offset into vcpu->arch */
 243         UASM_i_ADDIU(&p, K1, A1, offsetof(struct kvm_vcpu, arch));
 244 
 245         /*
 246          * Save the host stack to VCPU, used for exception processing
 247          * when we exit from the Guest
 248          */
 249         UASM_i_SW(&p, SP, offsetof(struct kvm_vcpu_arch, host_stack), K1);
 250 
 251         /* Save the kernel gp as well */
 252         UASM_i_SW(&p, GP, offsetof(struct kvm_vcpu_arch, host_gp), K1);
 253 
 254         /*
 255          * Setup status register for running the guest in UM, interrupts
 256          * are disabled
 257          */
 258         UASM_i_LA(&p, K0, ST0_EXL | KSU_USER | ST0_BEV | ST0_KX_IF_64);
 259         uasm_i_mtc0(&p, K0, C0_STATUS);
 260         uasm_i_ehb(&p);
 261 
 262         /* load up the new EBASE */
 263         UASM_i_LW(&p, K0, offsetof(struct kvm_vcpu_arch, guest_ebase), K1);
 264         build_set_exc_base(&p, K0);
 265 
 266         /*
 267          * Now that the new EBASE has been loaded, unset BEV, set
 268          * interrupt mask as it was but make sure that timer interrupts
 269          * are enabled
 270          */
 271         uasm_i_addiu(&p, K0, ZERO, ST0_EXL | KSU_USER | ST0_IE | ST0_KX_IF_64);
 272         uasm_i_andi(&p, V0, V0, ST0_IM);
 273         uasm_i_or(&p, K0, K0, V0);
 274         uasm_i_mtc0(&p, K0, C0_STATUS);
 275         uasm_i_ehb(&p);
 276 
 277         p = kvm_mips_build_enter_guest(p);
 278 
 279         return p;
 280 }
 281 
 282 /**
 283  * kvm_mips_build_enter_guest() - Assemble code to resume guest execution.
 284  * @addr:       Address to start writing code.
 285  *
 286  * Assemble the code to resume guest execution. This code is common between the
 287  * initial entry into the guest from the host, and returning from the exit
 288  * handler back to the guest.
 289  *
 290  * Returns:     Next address after end of written function.
 291  */
 292 static void *kvm_mips_build_enter_guest(void *addr)
 293 {
 294         u32 *p = addr;
 295         unsigned int i;
 296         struct uasm_label labels[2];
 297         struct uasm_reloc relocs[2];
 298         struct uasm_label __maybe_unused *l = labels;
 299         struct uasm_reloc __maybe_unused *r = relocs;
 300 
 301         memset(labels, 0, sizeof(labels));
 302         memset(relocs, 0, sizeof(relocs));
 303 
 304         /* Set Guest EPC */
 305         UASM_i_LW(&p, T0, offsetof(struct kvm_vcpu_arch, pc), K1);
 306         UASM_i_MTC0(&p, T0, C0_EPC);
 307 
 308 #ifdef CONFIG_KVM_MIPS_VZ
 309         /* Save normal linux process pgd (VZ guarantees pgd_reg is set) */
 310         UASM_i_MFC0(&p, K0, c0_kscratch(), pgd_reg);
 311         UASM_i_SW(&p, K0, offsetof(struct kvm_vcpu_arch, host_pgd), K1);
 312 
 313         /*
 314          * Set up KVM GPA pgd.
 315          * This does roughly the same as TLBMISS_HANDLER_SETUP_PGD():
 316          * - call tlbmiss_handler_setup_pgd(mm->pgd)
 317          * - write mm->pgd into CP0_PWBase
 318          *
 319          * We keep S0 pointing at struct kvm so we can load the ASID below.
 320          */
 321         UASM_i_LW(&p, S0, (int)offsetof(struct kvm_vcpu, kvm) -
 322                           (int)offsetof(struct kvm_vcpu, arch), K1);
 323         UASM_i_LW(&p, A0, offsetof(struct kvm, arch.gpa_mm.pgd), S0);
 324         UASM_i_LA(&p, T9, (unsigned long)tlbmiss_handler_setup_pgd);
 325         uasm_i_jalr(&p, RA, T9);
 326         /* delay slot */
 327         if (cpu_has_htw)
 328                 UASM_i_MTC0(&p, A0, C0_PWBASE);
 329         else
 330                 uasm_i_nop(&p);
 331 
 332         /* Set GM bit to setup eret to VZ guest context */
 333         uasm_i_addiu(&p, V1, ZERO, 1);
 334         uasm_i_mfc0(&p, K0, C0_GUESTCTL0);
 335         uasm_i_ins(&p, K0, V1, MIPS_GCTL0_GM_SHIFT, 1);
 336         uasm_i_mtc0(&p, K0, C0_GUESTCTL0);
 337 
 338         if (cpu_has_guestid) {
 339                 /*
 340                  * Set root mode GuestID, so that root TLB refill handler can
 341                  * use the correct GuestID in the root TLB.
 342                  */
 343 
 344                 /* Get current GuestID */
 345                 uasm_i_mfc0(&p, T0, C0_GUESTCTL1);
 346                 /* Set GuestCtl1.RID = GuestCtl1.ID */
 347                 uasm_i_ext(&p, T1, T0, MIPS_GCTL1_ID_SHIFT,
 348                            MIPS_GCTL1_ID_WIDTH);
 349                 uasm_i_ins(&p, T0, T1, MIPS_GCTL1_RID_SHIFT,
 350                            MIPS_GCTL1_RID_WIDTH);
 351                 uasm_i_mtc0(&p, T0, C0_GUESTCTL1);
 352 
 353                 /* GuestID handles dealiasing so we don't need to touch ASID */
 354                 goto skip_asid_restore;
 355         }
 356 
 357         /* Root ASID Dealias (RAD) */
 358 
 359         /* Save host ASID */
 360         UASM_i_MFC0(&p, K0, C0_ENTRYHI);
 361         UASM_i_SW(&p, K0, offsetof(struct kvm_vcpu_arch, host_entryhi),
 362                   K1);
 363 
 364         /* Set the root ASID for the Guest */
 365         UASM_i_ADDIU(&p, T1, S0,
 366                      offsetof(struct kvm, arch.gpa_mm.context.asid));
 367 #else
 368         /* Set the ASID for the Guest Kernel or User */
 369         UASM_i_LW(&p, T0, offsetof(struct kvm_vcpu_arch, cop0), K1);
 370         UASM_i_LW(&p, T0, offsetof(struct mips_coproc, reg[MIPS_CP0_STATUS][0]),
 371                   T0);
 372         uasm_i_andi(&p, T0, T0, KSU_USER | ST0_ERL | ST0_EXL);
 373         uasm_i_xori(&p, T0, T0, KSU_USER);
 374         uasm_il_bnez(&p, &r, T0, label_kernel_asid);
 375          UASM_i_ADDIU(&p, T1, K1, offsetof(struct kvm_vcpu_arch,
 376                                            guest_kernel_mm.context.asid));
 377         /* else user */
 378         UASM_i_ADDIU(&p, T1, K1, offsetof(struct kvm_vcpu_arch,
 379                                           guest_user_mm.context.asid));
 380         uasm_l_kernel_asid(&l, p);
 381 #endif
 382 
 383         /* t1: contains the base of the ASID array, need to get the cpu id  */
 384         /* smp_processor_id */
 385         uasm_i_lw(&p, T2, offsetof(struct thread_info, cpu), GP);
 386         /* index the ASID array */
 387         uasm_i_sll(&p, T2, T2, ilog2(sizeof(long)));
 388         UASM_i_ADDU(&p, T3, T1, T2);
 389         UASM_i_LW(&p, K0, 0, T3);
 390 #ifdef CONFIG_MIPS_ASID_BITS_VARIABLE
 391         /*
 392          * reuse ASID array offset
 393          * cpuinfo_mips is a multiple of sizeof(long)
 394          */
 395         uasm_i_addiu(&p, T3, ZERO, sizeof(struct cpuinfo_mips)/sizeof(long));
 396         uasm_i_mul(&p, T2, T2, T3);
 397 
 398         UASM_i_LA_mostly(&p, AT, (long)&cpu_data[0].asid_mask);
 399         UASM_i_ADDU(&p, AT, AT, T2);
 400         UASM_i_LW(&p, T2, uasm_rel_lo((long)&cpu_data[0].asid_mask), AT);
 401         uasm_i_and(&p, K0, K0, T2);
 402 #else
 403         uasm_i_andi(&p, K0, K0, MIPS_ENTRYHI_ASID);
 404 #endif
 405 
 406 #ifndef CONFIG_KVM_MIPS_VZ
 407         /*
 408          * Set up KVM T&E GVA pgd.
 409          * This does roughly the same as TLBMISS_HANDLER_SETUP_PGD():
 410          * - call tlbmiss_handler_setup_pgd(mm->pgd)
 411          * - but skips write into CP0_PWBase for now
 412          */
 413         UASM_i_LW(&p, A0, (int)offsetof(struct mm_struct, pgd) -
 414                           (int)offsetof(struct mm_struct, context.asid), T1);
 415 
 416         UASM_i_LA(&p, T9, (unsigned long)tlbmiss_handler_setup_pgd);
 417         uasm_i_jalr(&p, RA, T9);
 418          uasm_i_mtc0(&p, K0, C0_ENTRYHI);
 419 #else
 420         /* Set up KVM VZ root ASID (!guestid) */
 421         uasm_i_mtc0(&p, K0, C0_ENTRYHI);
 422 skip_asid_restore:
 423 #endif
 424         uasm_i_ehb(&p);
 425 
 426         /* Disable RDHWR access */
 427         uasm_i_mtc0(&p, ZERO, C0_HWRENA);
 428 
 429         /* load the guest context from VCPU and return */
 430         for (i = 1; i < 32; ++i) {
 431                 /* Guest k0/k1 loaded later */
 432                 if (i == K0 || i == K1)
 433                         continue;
 434                 UASM_i_LW(&p, i, offsetof(struct kvm_vcpu_arch, gprs[i]), K1);
 435         }
 436 
 437 #ifndef CONFIG_CPU_MIPSR6
 438         /* Restore hi/lo */
 439         UASM_i_LW(&p, K0, offsetof(struct kvm_vcpu_arch, hi), K1);
 440         uasm_i_mthi(&p, K0);
 441 
 442         UASM_i_LW(&p, K0, offsetof(struct kvm_vcpu_arch, lo), K1);
 443         uasm_i_mtlo(&p, K0);
 444 #endif
 445 
 446         /* Restore the guest's k0/k1 registers */
 447         UASM_i_LW(&p, K0, offsetof(struct kvm_vcpu_arch, gprs[K0]), K1);
 448         UASM_i_LW(&p, K1, offsetof(struct kvm_vcpu_arch, gprs[K1]), K1);
 449 
 450         /* Jump to guest */
 451         uasm_i_eret(&p);
 452 
 453         uasm_resolve_relocs(relocs, labels);
 454 
 455         return p;
 456 }
 457 
 458 /**
 459  * kvm_mips_build_tlb_refill_exception() - Assemble TLB refill handler.
 460  * @addr:       Address to start writing code.
 461  * @handler:    Address of common handler (within range of @addr).
 462  *
 463  * Assemble TLB refill exception fast path handler for guest execution.
 464  *
 465  * Returns:     Next address after end of written function.
 466  */
 467 void *kvm_mips_build_tlb_refill_exception(void *addr, void *handler)
 468 {
 469         u32 *p = addr;
 470         struct uasm_label labels[2];
 471         struct uasm_reloc relocs[2];
 472         struct uasm_label *l = labels;
 473         struct uasm_reloc *r = relocs;
 474 
 475         memset(labels, 0, sizeof(labels));
 476         memset(relocs, 0, sizeof(relocs));
 477 
 478         /* Save guest k1 into scratch register */
 479         UASM_i_MTC0(&p, K1, scratch_tmp[0], scratch_tmp[1]);
 480 
 481         /* Get the VCPU pointer from the VCPU scratch register */
 482         UASM_i_MFC0(&p, K1, scratch_vcpu[0], scratch_vcpu[1]);
 483 
 484         /* Save guest k0 into VCPU structure */
 485         UASM_i_SW(&p, K0, offsetof(struct kvm_vcpu, arch.gprs[K0]), K1);
 486 
 487         /*
 488          * Some of the common tlbex code uses current_cpu_type(). For KVM we
 489          * assume symmetry and just disable preemption to silence the warning.
 490          */
 491         preempt_disable();
 492 
 493         /*
 494          * Now for the actual refill bit. A lot of this can be common with the
 495          * Linux TLB refill handler, however we don't need to handle so many
 496          * cases. We only need to handle user mode refills, and user mode runs
 497          * with 32-bit addressing.
 498          *
 499          * Therefore the branch to label_vmalloc generated by build_get_pmde64()
 500          * that isn't resolved should never actually get taken and is harmless
 501          * to leave in place for now.
 502          */
 503 
 504 #ifdef CONFIG_64BIT
 505         build_get_pmde64(&p, &l, &r, K0, K1); /* get pmd in K1 */
 506 #else
 507         build_get_pgde32(&p, K0, K1); /* get pgd in K1 */
 508 #endif
 509 
 510         /* we don't support huge pages yet */
 511 
 512         build_get_ptep(&p, K0, K1);
 513         build_update_entries(&p, K0, K1);
 514         build_tlb_write_entry(&p, &l, &r, tlb_random);
 515 
 516         preempt_enable();
 517 
 518         /* Get the VCPU pointer from the VCPU scratch register again */
 519         UASM_i_MFC0(&p, K1, scratch_vcpu[0], scratch_vcpu[1]);
 520 
 521         /* Restore the guest's k0/k1 registers */
 522         UASM_i_LW(&p, K0, offsetof(struct kvm_vcpu, arch.gprs[K0]), K1);
 523         uasm_i_ehb(&p);
 524         UASM_i_MFC0(&p, K1, scratch_tmp[0], scratch_tmp[1]);
 525 
 526         /* Jump to guest */
 527         uasm_i_eret(&p);
 528 
 529         return p;
 530 }
 531 
 532 /**
 533  * kvm_mips_build_exception() - Assemble first level guest exception handler.
 534  * @addr:       Address to start writing code.
 535  * @handler:    Address of common handler (within range of @addr).
 536  *
 537  * Assemble exception vector code for guest execution. The generated vector will
 538  * branch to the common exception handler generated by kvm_mips_build_exit().
 539  *
 540  * Returns:     Next address after end of written function.
 541  */
 542 void *kvm_mips_build_exception(void *addr, void *handler)
 543 {
 544         u32 *p = addr;
 545         struct uasm_label labels[2];
 546         struct uasm_reloc relocs[2];
 547         struct uasm_label *l = labels;
 548         struct uasm_reloc *r = relocs;
 549 
 550         memset(labels, 0, sizeof(labels));
 551         memset(relocs, 0, sizeof(relocs));
 552 
 553         /* Save guest k1 into scratch register */
 554         UASM_i_MTC0(&p, K1, scratch_tmp[0], scratch_tmp[1]);
 555 
 556         /* Get the VCPU pointer from the VCPU scratch register */
 557         UASM_i_MFC0(&p, K1, scratch_vcpu[0], scratch_vcpu[1]);
 558         UASM_i_ADDIU(&p, K1, K1, offsetof(struct kvm_vcpu, arch));
 559 
 560         /* Save guest k0 into VCPU structure */
 561         UASM_i_SW(&p, K0, offsetof(struct kvm_vcpu_arch, gprs[K0]), K1);
 562 
 563         /* Branch to the common handler */
 564         uasm_il_b(&p, &r, label_exit_common);
 565          uasm_i_nop(&p);
 566 
 567         uasm_l_exit_common(&l, handler);
 568         uasm_resolve_relocs(relocs, labels);
 569 
 570         return p;
 571 }
 572 
 573 /**
 574  * kvm_mips_build_exit() - Assemble common guest exit handler.
 575  * @addr:       Address to start writing code.
 576  *
 577  * Assemble the generic guest exit handling code. This is called by the
 578  * exception vectors (generated by kvm_mips_build_exception()), and calls
 579  * kvm_mips_handle_exit(), then either resumes the guest or returns to the host
 580  * depending on the return value.
 581  *
 582  * Returns:     Next address after end of written function.
 583  */
 584 void *kvm_mips_build_exit(void *addr)
 585 {
 586         u32 *p = addr;
 587         unsigned int i;
 588         struct uasm_label labels[3];
 589         struct uasm_reloc relocs[3];
 590         struct uasm_label *l = labels;
 591         struct uasm_reloc *r = relocs;
 592 
 593         memset(labels, 0, sizeof(labels));
 594         memset(relocs, 0, sizeof(relocs));
 595 
 596         /*
 597          * Generic Guest exception handler. We end up here when the guest
 598          * does something that causes a trap to kernel mode.
 599          *
 600          * Both k0/k1 registers will have already been saved (k0 into the vcpu
 601          * structure, and k1 into the scratch_tmp register).
 602          *
 603          * The k1 register will already contain the kvm_vcpu_arch pointer.
 604          */
 605 
 606         /* Start saving Guest context to VCPU */
 607         for (i = 0; i < 32; ++i) {
 608                 /* Guest k0/k1 saved later */
 609                 if (i == K0 || i == K1)
 610                         continue;
 611                 UASM_i_SW(&p, i, offsetof(struct kvm_vcpu_arch, gprs[i]), K1);
 612         }
 613 
 614 #ifndef CONFIG_CPU_MIPSR6
 615         /* We need to save hi/lo and restore them on the way out */
 616         uasm_i_mfhi(&p, T0);
 617         UASM_i_SW(&p, T0, offsetof(struct kvm_vcpu_arch, hi), K1);
 618 
 619         uasm_i_mflo(&p, T0);
 620         UASM_i_SW(&p, T0, offsetof(struct kvm_vcpu_arch, lo), K1);
 621 #endif
 622 
 623         /* Finally save guest k1 to VCPU */
 624         uasm_i_ehb(&p);
 625         UASM_i_MFC0(&p, T0, scratch_tmp[0], scratch_tmp[1]);
 626         UASM_i_SW(&p, T0, offsetof(struct kvm_vcpu_arch, gprs[K1]), K1);
 627 
 628         /* Now that context has been saved, we can use other registers */
 629 
 630         /* Restore vcpu */
 631         UASM_i_MFC0(&p, S1, scratch_vcpu[0], scratch_vcpu[1]);
 632 
 633         /* Restore run (vcpu->run) */
 634         UASM_i_LW(&p, S0, offsetof(struct kvm_vcpu, run), S1);
 635 
 636         /*
 637          * Save Host level EPC, BadVaddr and Cause to VCPU, useful to process
 638          * the exception
 639          */
 640         UASM_i_MFC0(&p, K0, C0_EPC);
 641         UASM_i_SW(&p, K0, offsetof(struct kvm_vcpu_arch, pc), K1);
 642 
 643         UASM_i_MFC0(&p, K0, C0_BADVADDR);
 644         UASM_i_SW(&p, K0, offsetof(struct kvm_vcpu_arch, host_cp0_badvaddr),
 645                   K1);
 646 
 647         uasm_i_mfc0(&p, K0, C0_CAUSE);
 648         uasm_i_sw(&p, K0, offsetof(struct kvm_vcpu_arch, host_cp0_cause), K1);
 649 
 650         if (cpu_has_badinstr) {
 651                 uasm_i_mfc0(&p, K0, C0_BADINSTR);
 652                 uasm_i_sw(&p, K0, offsetof(struct kvm_vcpu_arch,
 653                                            host_cp0_badinstr), K1);
 654         }
 655 
 656         if (cpu_has_badinstrp) {
 657                 uasm_i_mfc0(&p, K0, C0_BADINSTRP);
 658                 uasm_i_sw(&p, K0, offsetof(struct kvm_vcpu_arch,
 659                                            host_cp0_badinstrp), K1);
 660         }
 661 
 662         /* Now restore the host state just enough to run the handlers */
 663 
 664         /* Switch EBASE to the one used by Linux */
 665         /* load up the host EBASE */
 666         uasm_i_mfc0(&p, V0, C0_STATUS);
 667 
 668         uasm_i_lui(&p, AT, ST0_BEV >> 16);
 669         uasm_i_or(&p, K0, V0, AT);
 670 
 671         uasm_i_mtc0(&p, K0, C0_STATUS);
 672         uasm_i_ehb(&p);
 673 
 674         UASM_i_LA_mostly(&p, K0, (long)&ebase);
 675         UASM_i_LW(&p, K0, uasm_rel_lo((long)&ebase), K0);
 676         build_set_exc_base(&p, K0);
 677 
 678         if (raw_cpu_has_fpu) {
 679                 /*
 680                  * If FPU is enabled, save FCR31 and clear it so that later
 681                  * ctc1's don't trigger FPE for pending exceptions.
 682                  */
 683                 uasm_i_lui(&p, AT, ST0_CU1 >> 16);
 684                 uasm_i_and(&p, V1, V0, AT);
 685                 uasm_il_beqz(&p, &r, V1, label_fpu_1);
 686                  uasm_i_nop(&p);
 687                 uasm_i_cfc1(&p, T0, 31);
 688                 uasm_i_sw(&p, T0, offsetof(struct kvm_vcpu_arch, fpu.fcr31),
 689                           K1);
 690                 uasm_i_ctc1(&p, ZERO, 31);
 691                 uasm_l_fpu_1(&l, p);
 692         }
 693 
 694         if (cpu_has_msa) {
 695                 /*
 696                  * If MSA is enabled, save MSACSR and clear it so that later
 697                  * instructions don't trigger MSAFPE for pending exceptions.
 698                  */
 699                 uasm_i_mfc0(&p, T0, C0_CONFIG5);
 700                 uasm_i_ext(&p, T0, T0, 27, 1); /* MIPS_CONF5_MSAEN */
 701                 uasm_il_beqz(&p, &r, T0, label_msa_1);
 702                  uasm_i_nop(&p);
 703                 uasm_i_cfcmsa(&p, T0, MSA_CSR);
 704                 uasm_i_sw(&p, T0, offsetof(struct kvm_vcpu_arch, fpu.msacsr),
 705                           K1);
 706                 uasm_i_ctcmsa(&p, MSA_CSR, ZERO);
 707                 uasm_l_msa_1(&l, p);
 708         }
 709 
 710 #ifdef CONFIG_KVM_MIPS_VZ
 711         /* Restore host ASID */
 712         if (!cpu_has_guestid) {
 713                 UASM_i_LW(&p, K0, offsetof(struct kvm_vcpu_arch, host_entryhi),
 714                           K1);
 715                 UASM_i_MTC0(&p, K0, C0_ENTRYHI);
 716         }
 717 
 718         /*
 719          * Set up normal Linux process pgd.
 720          * This does roughly the same as TLBMISS_HANDLER_SETUP_PGD():
 721          * - call tlbmiss_handler_setup_pgd(mm->pgd)
 722          * - write mm->pgd into CP0_PWBase
 723          */
 724         UASM_i_LW(&p, A0,
 725                   offsetof(struct kvm_vcpu_arch, host_pgd), K1);
 726         UASM_i_LA(&p, T9, (unsigned long)tlbmiss_handler_setup_pgd);
 727         uasm_i_jalr(&p, RA, T9);
 728         /* delay slot */
 729         if (cpu_has_htw)
 730                 UASM_i_MTC0(&p, A0, C0_PWBASE);
 731         else
 732                 uasm_i_nop(&p);
 733 
 734         /* Clear GM bit so we don't enter guest mode when EXL is cleared */
 735         uasm_i_mfc0(&p, K0, C0_GUESTCTL0);
 736         uasm_i_ins(&p, K0, ZERO, MIPS_GCTL0_GM_SHIFT, 1);
 737         uasm_i_mtc0(&p, K0, C0_GUESTCTL0);
 738 
 739         /* Save GuestCtl0 so we can access GExcCode after CPU migration */
 740         uasm_i_sw(&p, K0,
 741                   offsetof(struct kvm_vcpu_arch, host_cp0_guestctl0), K1);
 742 
 743         if (cpu_has_guestid) {
 744                 /*
 745                  * Clear root mode GuestID, so that root TLB operations use the
 746                  * root GuestID in the root TLB.
 747                  */
 748                 uasm_i_mfc0(&p, T0, C0_GUESTCTL1);
 749                 /* Set GuestCtl1.RID = MIPS_GCTL1_ROOT_GUESTID (i.e. 0) */
 750                 uasm_i_ins(&p, T0, ZERO, MIPS_GCTL1_RID_SHIFT,
 751                            MIPS_GCTL1_RID_WIDTH);
 752                 uasm_i_mtc0(&p, T0, C0_GUESTCTL1);
 753         }
 754 #endif
 755 
 756         /* Now that the new EBASE has been loaded, unset BEV and KSU_USER */
 757         uasm_i_addiu(&p, AT, ZERO, ~(ST0_EXL | KSU_USER | ST0_IE));
 758         uasm_i_and(&p, V0, V0, AT);
 759         uasm_i_lui(&p, AT, ST0_CU0 >> 16);
 760         uasm_i_or(&p, V0, V0, AT);
 761 #ifdef CONFIG_64BIT
 762         uasm_i_ori(&p, V0, V0, ST0_SX | ST0_UX);
 763 #endif
 764         uasm_i_mtc0(&p, V0, C0_STATUS);
 765         uasm_i_ehb(&p);
 766 
 767         /* Load up host GP */
 768         UASM_i_LW(&p, GP, offsetof(struct kvm_vcpu_arch, host_gp), K1);
 769 
 770         /* Need a stack before we can jump to "C" */
 771         UASM_i_LW(&p, SP, offsetof(struct kvm_vcpu_arch, host_stack), K1);
 772 
 773         /* Saved host state */
 774         UASM_i_ADDIU(&p, SP, SP, -(int)sizeof(struct pt_regs));
 775 
 776         /*
 777          * XXXKYMA do we need to load the host ASID, maybe not because the
 778          * kernel entries are marked GLOBAL, need to verify
 779          */
 780 
 781         /* Restore host scratch registers, as we'll have clobbered them */
 782         kvm_mips_build_restore_scratch(&p, K0, SP);
 783 
 784         /* Restore RDHWR access */
 785         UASM_i_LA_mostly(&p, K0, (long)&hwrena);
 786         uasm_i_lw(&p, K0, uasm_rel_lo((long)&hwrena), K0);
 787         uasm_i_mtc0(&p, K0, C0_HWRENA);
 788 
 789         /* Jump to handler */
 790         /*
 791          * XXXKYMA: not sure if this is safe, how large is the stack??
 792          * Now jump to the kvm_mips_handle_exit() to see if we can deal
 793          * with this in the kernel
 794          */
 795         uasm_i_move(&p, A0, S0);
 796         uasm_i_move(&p, A1, S1);
 797         UASM_i_LA(&p, T9, (unsigned long)kvm_mips_handle_exit);
 798         uasm_i_jalr(&p, RA, T9);
 799          UASM_i_ADDIU(&p, SP, SP, -CALLFRAME_SIZ);
 800 
 801         uasm_resolve_relocs(relocs, labels);
 802 
 803         p = kvm_mips_build_ret_from_exit(p);
 804 
 805         return p;
 806 }
 807 
 808 /**
 809  * kvm_mips_build_ret_from_exit() - Assemble guest exit return handler.
 810  * @addr:       Address to start writing code.
 811  *
 812  * Assemble the code to handle the return from kvm_mips_handle_exit(), either
 813  * resuming the guest or returning to the host depending on the return value.
 814  *
 815  * Returns:     Next address after end of written function.
 816  */
 817 static void *kvm_mips_build_ret_from_exit(void *addr)
 818 {
 819         u32 *p = addr;
 820         struct uasm_label labels[2];
 821         struct uasm_reloc relocs[2];
 822         struct uasm_label *l = labels;
 823         struct uasm_reloc *r = relocs;
 824 
 825         memset(labels, 0, sizeof(labels));
 826         memset(relocs, 0, sizeof(relocs));
 827 
 828         /* Return from handler Make sure interrupts are disabled */
 829         uasm_i_di(&p, ZERO);
 830         uasm_i_ehb(&p);
 831 
 832         /*
 833          * XXXKYMA: k0/k1 could have been blown away if we processed
 834          * an exception while we were handling the exception from the
 835          * guest, reload k1
 836          */
 837 
 838         uasm_i_move(&p, K1, S1);
 839         UASM_i_ADDIU(&p, K1, K1, offsetof(struct kvm_vcpu, arch));
 840 
 841         /*
 842          * Check return value, should tell us if we are returning to the
 843          * host (handle I/O etc)or resuming the guest
 844          */
 845         uasm_i_andi(&p, T0, V0, RESUME_HOST);
 846         uasm_il_bnez(&p, &r, T0, label_return_to_host);
 847          uasm_i_nop(&p);
 848 
 849         p = kvm_mips_build_ret_to_guest(p);
 850 
 851         uasm_l_return_to_host(&l, p);
 852         p = kvm_mips_build_ret_to_host(p);
 853 
 854         uasm_resolve_relocs(relocs, labels);
 855 
 856         return p;
 857 }
 858 
 859 /**
 860  * kvm_mips_build_ret_to_guest() - Assemble code to return to the guest.
 861  * @addr:       Address to start writing code.
 862  *
 863  * Assemble the code to handle return from the guest exit handler
 864  * (kvm_mips_handle_exit()) back to the guest.
 865  *
 866  * Returns:     Next address after end of written function.
 867  */
 868 static void *kvm_mips_build_ret_to_guest(void *addr)
 869 {
 870         u32 *p = addr;
 871 
 872         /* Put the saved pointer to vcpu (s1) back into the scratch register */
 873         UASM_i_MTC0(&p, S1, scratch_vcpu[0], scratch_vcpu[1]);
 874 
 875         /* Load up the Guest EBASE to minimize the window where BEV is set */
 876         UASM_i_LW(&p, T0, offsetof(struct kvm_vcpu_arch, guest_ebase), K1);
 877 
 878         /* Switch EBASE back to the one used by KVM */
 879         uasm_i_mfc0(&p, V1, C0_STATUS);
 880         uasm_i_lui(&p, AT, ST0_BEV >> 16);
 881         uasm_i_or(&p, K0, V1, AT);
 882         uasm_i_mtc0(&p, K0, C0_STATUS);
 883         uasm_i_ehb(&p);
 884         build_set_exc_base(&p, T0);
 885 
 886         /* Setup status register for running guest in UM */
 887         uasm_i_ori(&p, V1, V1, ST0_EXL | KSU_USER | ST0_IE);
 888         UASM_i_LA(&p, AT, ~(ST0_CU0 | ST0_MX | ST0_SX | ST0_UX));
 889         uasm_i_and(&p, V1, V1, AT);
 890         uasm_i_mtc0(&p, V1, C0_STATUS);
 891         uasm_i_ehb(&p);
 892 
 893         p = kvm_mips_build_enter_guest(p);
 894 
 895         return p;
 896 }
 897 
 898 /**
 899  * kvm_mips_build_ret_to_host() - Assemble code to return to the host.
 900  * @addr:       Address to start writing code.
 901  *
 902  * Assemble the code to handle return from the guest exit handler
 903  * (kvm_mips_handle_exit()) back to the host, i.e. to the caller of the vcpu_run
 904  * function generated by kvm_mips_build_vcpu_run().
 905  *
 906  * Returns:     Next address after end of written function.
 907  */
 908 static void *kvm_mips_build_ret_to_host(void *addr)
 909 {
 910         u32 *p = addr;
 911         unsigned int i;
 912 
 913         /* EBASE is already pointing to Linux */
 914         UASM_i_LW(&p, K1, offsetof(struct kvm_vcpu_arch, host_stack), K1);
 915         UASM_i_ADDIU(&p, K1, K1, -(int)sizeof(struct pt_regs));
 916 
 917         /*
 918          * r2/v0 is the return code, shift it down by 2 (arithmetic)
 919          * to recover the err code
 920          */
 921         uasm_i_sra(&p, K0, V0, 2);
 922         uasm_i_move(&p, V0, K0);
 923 
 924         /* Load context saved on the host stack */
 925         for (i = 16; i < 31; ++i) {
 926                 if (i == 24)
 927                         i = 28;
 928                 UASM_i_LW(&p, i, offsetof(struct pt_regs, regs[i]), K1);
 929         }
 930 
 931         /* Restore RDHWR access */
 932         UASM_i_LA_mostly(&p, K0, (long)&hwrena);
 933         uasm_i_lw(&p, K0, uasm_rel_lo((long)&hwrena), K0);
 934         uasm_i_mtc0(&p, K0, C0_HWRENA);
 935 
 936         /* Restore RA, which is the address we will return to */
 937         UASM_i_LW(&p, RA, offsetof(struct pt_regs, regs[RA]), K1);
 938         uasm_i_jr(&p, RA);
 939          uasm_i_nop(&p);
 940 
 941         return p;
 942 }
 943