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/mipsregs.h>
17 #include <asm/mmu_context.h>
18 #include <asm/msa.h>
19 #include <asm/regdef.h>
20 #include <asm/setup.h>
21 #include <asm/tlbex.h>
22 #include <asm/uasm.h>
23
24 #define CALLFRAME_SIZ 32
25
26 static unsigned int scratch_vcpu[2] = { C0_DDATALO };
27 static unsigned int scratch_tmp[2] = { C0_ERROREPC };
28
29 enum label_id {
30 label_fpu_1 = 1,
31 label_msa_1,
32 label_return_to_host,
33 label_kernel_asid,
34 label_exit_common,
35 };
36
37 UASM_L_LA(_fpu_1)
38 UASM_L_LA(_msa_1)
39 UASM_L_LA(_return_to_host)
40 UASM_L_LA(_kernel_asid)
41 UASM_L_LA(_exit_common)
42
43 static void *kvm_mips_build_enter_guest(void *addr);
44 static void *kvm_mips_build_ret_from_exit(void *addr);
45 static void *kvm_mips_build_ret_to_guest(void *addr);
46 static void *kvm_mips_build_ret_to_host(void *addr);
47
48 /*
49 * The version of this function in tlbex.c uses current_cpu_type(), but for KVM
50 * we assume symmetry.
51 */
c0_kscratch(void)52 static int c0_kscratch(void)
53 {
54 return 31;
55 }
56
57 /**
58 * kvm_mips_entry_setup() - Perform global setup for entry code.
59 *
60 * Perform global setup for entry code, such as choosing a scratch register.
61 *
62 * Returns: 0 on success.
63 * -errno on failure.
64 */
kvm_mips_entry_setup(void)65 int kvm_mips_entry_setup(void)
66 {
67 /*
68 * We prefer to use KScratchN registers if they are available over the
69 * defaults above, which may not work on all cores.
70 */
71 unsigned int kscratch_mask = cpu_data[0].kscratch_mask;
72
73 if (pgd_reg != -1)
74 kscratch_mask &= ~BIT(pgd_reg);
75
76 /* Pick a scratch register for storing VCPU */
77 if (kscratch_mask) {
78 scratch_vcpu[0] = c0_kscratch();
79 scratch_vcpu[1] = ffs(kscratch_mask) - 1;
80 kscratch_mask &= ~BIT(scratch_vcpu[1]);
81 }
82
83 /* Pick a scratch register to use as a temp for saving state */
84 if (kscratch_mask) {
85 scratch_tmp[0] = c0_kscratch();
86 scratch_tmp[1] = ffs(kscratch_mask) - 1;
87 kscratch_mask &= ~BIT(scratch_tmp[1]);
88 }
89
90 return 0;
91 }
92
kvm_mips_build_save_scratch(u32 ** p,unsigned int tmp,unsigned int frame)93 static void kvm_mips_build_save_scratch(u32 **p, unsigned int tmp,
94 unsigned int frame)
95 {
96 /* Save the VCPU scratch register value in cp0_epc of the stack frame */
97 UASM_i_MFC0(p, tmp, scratch_vcpu[0], scratch_vcpu[1]);
98 UASM_i_SW(p, tmp, offsetof(struct pt_regs, cp0_epc), frame);
99
100 /* Save the temp scratch register value in cp0_cause of stack frame */
101 if (scratch_tmp[0] == c0_kscratch()) {
102 UASM_i_MFC0(p, tmp, scratch_tmp[0], scratch_tmp[1]);
103 UASM_i_SW(p, tmp, offsetof(struct pt_regs, cp0_cause), frame);
104 }
105 }
106
kvm_mips_build_restore_scratch(u32 ** p,unsigned int tmp,unsigned int frame)107 static void kvm_mips_build_restore_scratch(u32 **p, unsigned int tmp,
108 unsigned int frame)
109 {
110 /*
111 * Restore host scratch register values saved by
112 * kvm_mips_build_save_scratch().
113 */
114 UASM_i_LW(p, tmp, offsetof(struct pt_regs, cp0_epc), frame);
115 UASM_i_MTC0(p, tmp, scratch_vcpu[0], scratch_vcpu[1]);
116
117 if (scratch_tmp[0] == c0_kscratch()) {
118 UASM_i_LW(p, tmp, offsetof(struct pt_regs, cp0_cause), frame);
119 UASM_i_MTC0(p, tmp, scratch_tmp[0], scratch_tmp[1]);
120 }
121 }
122
123 /**
124 * build_set_exc_base() - Assemble code to write exception base address.
125 * @p: Code buffer pointer.
126 * @reg: Source register (generated code may set WG bit in @reg).
127 *
128 * Assemble code to modify the exception base address in the EBase register,
129 * using the appropriately sized access and setting the WG bit if necessary.
130 */
build_set_exc_base(u32 ** p,unsigned int reg)131 static inline void build_set_exc_base(u32 **p, unsigned int reg)
132 {
133 if (cpu_has_ebase_wg) {
134 /* Set WG so that all the bits get written */
135 uasm_i_ori(p, reg, reg, MIPS_EBASE_WG);
136 UASM_i_MTC0(p, reg, C0_EBASE);
137 } else {
138 uasm_i_mtc0(p, reg, C0_EBASE);
139 }
140 }
141
142 /**
143 * kvm_mips_build_vcpu_run() - Assemble function to start running a guest VCPU.
144 * @addr: Address to start writing code.
145 *
146 * Assemble the start of the vcpu_run function to run a guest VCPU. The function
147 * conforms to the following prototype:
148 *
149 * int vcpu_run(struct kvm_vcpu *vcpu);
150 *
151 * The exit from the guest and return to the caller is handled by the code
152 * generated by kvm_mips_build_ret_to_host().
153 *
154 * Returns: Next address after end of written function.
155 */
kvm_mips_build_vcpu_run(void * addr)156 void *kvm_mips_build_vcpu_run(void *addr)
157 {
158 u32 *p = addr;
159 unsigned int i;
160
161 /*
162 * GPR_A0: vcpu
163 */
164
165 /* k0/k1 not being used in host kernel context */
166 UASM_i_ADDIU(&p, GPR_K1, GPR_SP, -(int)sizeof(struct pt_regs));
167 for (i = 16; i < 32; ++i) {
168 if (i == 24)
169 i = 28;
170 UASM_i_SW(&p, i, offsetof(struct pt_regs, regs[i]), GPR_K1);
171 }
172
173 /* Save host status */
174 uasm_i_mfc0(&p, GPR_V0, C0_STATUS);
175 UASM_i_SW(&p, GPR_V0, offsetof(struct pt_regs, cp0_status), GPR_K1);
176
177 /* Save scratch registers, will be used to store pointer to vcpu etc */
178 kvm_mips_build_save_scratch(&p, GPR_V1, GPR_K1);
179
180 /* VCPU scratch register has pointer to vcpu */
181 UASM_i_MTC0(&p, GPR_A0, scratch_vcpu[0], scratch_vcpu[1]);
182
183 /* Offset into vcpu->arch */
184 UASM_i_ADDIU(&p, GPR_K1, GPR_A0, offsetof(struct kvm_vcpu, arch));
185
186 /*
187 * Save the host stack to VCPU, used for exception processing
188 * when we exit from the Guest
189 */
190 UASM_i_SW(&p, GPR_SP, offsetof(struct kvm_vcpu_arch, host_stack), GPR_K1);
191
192 /* Save the kernel gp as well */
193 UASM_i_SW(&p, GPR_GP, offsetof(struct kvm_vcpu_arch, host_gp), GPR_K1);
194
195 /*
196 * Setup status register for running the guest in UM, interrupts
197 * are disabled
198 */
199 UASM_i_LA(&p, GPR_K0, ST0_EXL | KSU_USER | ST0_BEV | ST0_KX_IF_64);
200 uasm_i_mtc0(&p, GPR_K0, C0_STATUS);
201 uasm_i_ehb(&p);
202
203 /* load up the new EBASE */
204 UASM_i_LW(&p, GPR_K0, offsetof(struct kvm_vcpu_arch, guest_ebase), GPR_K1);
205 build_set_exc_base(&p, GPR_K0);
206
207 /*
208 * Now that the new EBASE has been loaded, unset BEV, set
209 * interrupt mask as it was but make sure that timer interrupts
210 * are enabled
211 */
212 uasm_i_addiu(&p, GPR_K0, GPR_ZERO, ST0_EXL | KSU_USER | ST0_IE | ST0_KX_IF_64);
213 uasm_i_andi(&p, GPR_V0, GPR_V0, ST0_IM);
214 uasm_i_or(&p, GPR_K0, GPR_K0, GPR_V0);
215 uasm_i_mtc0(&p, GPR_K0, C0_STATUS);
216 uasm_i_ehb(&p);
217
218 p = kvm_mips_build_enter_guest(p);
219
220 return p;
221 }
222
223 /**
224 * kvm_mips_build_enter_guest() - Assemble code to resume guest execution.
225 * @addr: Address to start writing code.
226 *
227 * Assemble the code to resume guest execution. This code is common between the
228 * initial entry into the guest from the host, and returning from the exit
229 * handler back to the guest.
230 *
231 * Returns: Next address after end of written function.
232 */
kvm_mips_build_enter_guest(void * addr)233 static void *kvm_mips_build_enter_guest(void *addr)
234 {
235 u32 *p = addr;
236 unsigned int i;
237 struct uasm_label labels[2];
238 struct uasm_reloc relocs[2];
239 struct uasm_label __maybe_unused *l = labels;
240 struct uasm_reloc __maybe_unused *r = relocs;
241
242 memset(labels, 0, sizeof(labels));
243 memset(relocs, 0, sizeof(relocs));
244
245 /* Set Guest EPC */
246 UASM_i_LW(&p, GPR_T0, offsetof(struct kvm_vcpu_arch, pc), GPR_K1);
247 UASM_i_MTC0(&p, GPR_T0, C0_EPC);
248
249 /* Save normal linux process pgd (VZ guarantees pgd_reg is set) */
250 if (cpu_has_ldpte)
251 UASM_i_MFC0(&p, GPR_K0, C0_PWBASE);
252 else
253 UASM_i_MFC0(&p, GPR_K0, c0_kscratch(), pgd_reg);
254 UASM_i_SW(&p, GPR_K0, offsetof(struct kvm_vcpu_arch, host_pgd), GPR_K1);
255
256 /*
257 * Set up KVM GPA pgd.
258 * This does roughly the same as TLBMISS_HANDLER_SETUP_PGD():
259 * - call tlbmiss_handler_setup_pgd(mm->pgd)
260 * - write mm->pgd into CP0_PWBase
261 *
262 * We keep GPR_S0 pointing at struct kvm so we can load the ASID below.
263 */
264 UASM_i_LW(&p, GPR_S0, (int)offsetof(struct kvm_vcpu, kvm) -
265 (int)offsetof(struct kvm_vcpu, arch), GPR_K1);
266 UASM_i_LW(&p, GPR_A0, offsetof(struct kvm, arch.gpa_mm.pgd), GPR_S0);
267 UASM_i_LA(&p, GPR_T9, (unsigned long)tlbmiss_handler_setup_pgd);
268 uasm_i_jalr(&p, GPR_RA, GPR_T9);
269 /* delay slot */
270 if (cpu_has_htw)
271 UASM_i_MTC0(&p, GPR_A0, C0_PWBASE);
272 else
273 uasm_i_nop(&p);
274
275 /* Set GM bit to setup eret to VZ guest context */
276 uasm_i_addiu(&p, GPR_V1, GPR_ZERO, 1);
277 uasm_i_mfc0(&p, GPR_K0, C0_GUESTCTL0);
278 uasm_i_ins(&p, GPR_K0, GPR_V1, MIPS_GCTL0_GM_SHIFT, 1);
279 uasm_i_mtc0(&p, GPR_K0, C0_GUESTCTL0);
280
281 if (cpu_has_guestid) {
282 /*
283 * Set root mode GuestID, so that root TLB refill handler can
284 * use the correct GuestID in the root TLB.
285 */
286
287 /* Get current GuestID */
288 uasm_i_mfc0(&p, GPR_T0, C0_GUESTCTL1);
289 /* Set GuestCtl1.RID = GuestCtl1.ID */
290 uasm_i_ext(&p, GPR_T1, GPR_T0, MIPS_GCTL1_ID_SHIFT,
291 MIPS_GCTL1_ID_WIDTH);
292 uasm_i_ins(&p, GPR_T0, GPR_T1, MIPS_GCTL1_RID_SHIFT,
293 MIPS_GCTL1_RID_WIDTH);
294 uasm_i_mtc0(&p, GPR_T0, C0_GUESTCTL1);
295
296 /* GuestID handles dealiasing so we don't need to touch ASID */
297 goto skip_asid_restore;
298 }
299
300 /* Root ASID Dealias (RAD) */
301
302 /* Save host ASID */
303 UASM_i_MFC0(&p, GPR_K0, C0_ENTRYHI);
304 UASM_i_SW(&p, GPR_K0, offsetof(struct kvm_vcpu_arch, host_entryhi),
305 GPR_K1);
306
307 /* Set the root ASID for the Guest */
308 UASM_i_ADDIU(&p, GPR_T1, GPR_S0,
309 offsetof(struct kvm, arch.gpa_mm.context.asid));
310
311 /* t1: contains the base of the ASID array, need to get the cpu id */
312 /* smp_processor_id */
313 uasm_i_lw(&p, GPR_T2, offsetof(struct thread_info, cpu), GPR_GP);
314 /* index the ASID array */
315 uasm_i_sll(&p, GPR_T2, GPR_T2, ilog2(sizeof(long)));
316 UASM_i_ADDU(&p, GPR_T3, GPR_T1, GPR_T2);
317 UASM_i_LW(&p, GPR_K0, 0, GPR_T3);
318 #ifdef CONFIG_MIPS_ASID_BITS_VARIABLE
319 /*
320 * reuse ASID array offset
321 * cpuinfo_mips is a multiple of sizeof(long)
322 */
323 uasm_i_addiu(&p, GPR_T3, GPR_ZERO, sizeof(struct cpuinfo_mips)/sizeof(long));
324 uasm_i_mul(&p, GPR_T2, GPR_T2, GPR_T3);
325
326 UASM_i_LA_mostly(&p, GPR_AT, (long)&cpu_data[0].asid_mask);
327 UASM_i_ADDU(&p, GPR_AT, GPR_AT, GPR_T2);
328 UASM_i_LW(&p, GPR_T2, uasm_rel_lo((long)&cpu_data[0].asid_mask), GPR_AT);
329 uasm_i_and(&p, GPR_K0, GPR_K0, GPR_T2);
330 #else
331 uasm_i_andi(&p, GPR_K0, GPR_K0, MIPS_ENTRYHI_ASID);
332 #endif
333
334 /* Set up KVM VZ root ASID (!guestid) */
335 uasm_i_mtc0(&p, GPR_K0, C0_ENTRYHI);
336 skip_asid_restore:
337 uasm_i_ehb(&p);
338
339 /* Disable RDHWR access */
340 uasm_i_mtc0(&p, GPR_ZERO, C0_HWRENA);
341
342 /* load the guest context from VCPU and return */
343 for (i = 1; i < 32; ++i) {
344 /* Guest k0/k1 loaded later */
345 if (i == GPR_K0 || i == GPR_K1)
346 continue;
347 UASM_i_LW(&p, i, offsetof(struct kvm_vcpu_arch, gprs[i]), GPR_K1);
348 }
349
350 #ifndef CONFIG_CPU_MIPSR6
351 /* Restore hi/lo */
352 UASM_i_LW(&p, GPR_K0, offsetof(struct kvm_vcpu_arch, hi), GPR_K1);
353 uasm_i_mthi(&p, GPR_K0);
354
355 UASM_i_LW(&p, GPR_K0, offsetof(struct kvm_vcpu_arch, lo), GPR_K1);
356 uasm_i_mtlo(&p, GPR_K0);
357 #endif
358
359 /* Restore the guest's k0/k1 registers */
360 UASM_i_LW(&p, GPR_K0, offsetof(struct kvm_vcpu_arch, gprs[GPR_K0]), GPR_K1);
361 UASM_i_LW(&p, GPR_K1, offsetof(struct kvm_vcpu_arch, gprs[GPR_K1]), GPR_K1);
362
363 /* Jump to guest */
364 uasm_i_eret(&p);
365
366 uasm_resolve_relocs(relocs, labels);
367
368 return p;
369 }
370
371 /**
372 * kvm_mips_build_tlb_refill_exception() - Assemble TLB refill handler.
373 * @addr: Address to start writing code.
374 * @handler: Address of common handler (within range of @addr).
375 *
376 * Assemble TLB refill exception fast path handler for guest execution.
377 *
378 * Returns: Next address after end of written function.
379 */
kvm_mips_build_tlb_refill_exception(void * addr,void * handler)380 void *kvm_mips_build_tlb_refill_exception(void *addr, void *handler)
381 {
382 u32 *p = addr;
383 struct uasm_label labels[2];
384 struct uasm_reloc relocs[2];
385 #ifndef CONFIG_CPU_LOONGSON64
386 struct uasm_label *l = labels;
387 struct uasm_reloc *r = relocs;
388 #endif
389
390 memset(labels, 0, sizeof(labels));
391 memset(relocs, 0, sizeof(relocs));
392
393 /* Save guest k1 into scratch register */
394 UASM_i_MTC0(&p, GPR_K1, scratch_tmp[0], scratch_tmp[1]);
395
396 /* Get the VCPU pointer from the VCPU scratch register */
397 UASM_i_MFC0(&p, GPR_K1, scratch_vcpu[0], scratch_vcpu[1]);
398
399 /* Save guest k0 into VCPU structure */
400 UASM_i_SW(&p, GPR_K0, offsetof(struct kvm_vcpu, arch.gprs[GPR_K0]), GPR_K1);
401
402 /*
403 * Some of the common tlbex code uses current_cpu_type(). For KVM we
404 * assume symmetry and just disable preemption to silence the warning.
405 */
406 preempt_disable();
407
408 #ifdef CONFIG_CPU_LOONGSON64
409 UASM_i_MFC0(&p, GPR_K1, C0_PGD);
410 uasm_i_lddir(&p, GPR_K0, GPR_K1, 3); /* global page dir */
411 #ifndef __PAGETABLE_PMD_FOLDED
412 uasm_i_lddir(&p, GPR_K1, GPR_K0, 1); /* middle page dir */
413 #endif
414 uasm_i_ldpte(&p, GPR_K1, 0); /* even */
415 uasm_i_ldpte(&p, GPR_K1, 1); /* odd */
416 uasm_i_tlbwr(&p);
417 #else
418 /*
419 * Now for the actual refill bit. A lot of this can be common with the
420 * Linux TLB refill handler, however we don't need to handle so many
421 * cases. We only need to handle user mode refills, and user mode runs
422 * with 32-bit addressing.
423 *
424 * Therefore the branch to label_vmalloc generated by build_get_pmde64()
425 * that isn't resolved should never actually get taken and is harmless
426 * to leave in place for now.
427 */
428
429 #ifdef CONFIG_64BIT
430 build_get_pmde64(&p, &l, &r, GPR_K0, GPR_K1); /* get pmd in GPR_K1 */
431 #else
432 build_get_pgde32(&p, GPR_K0, GPR_K1); /* get pgd in GPR_K1 */
433 #endif
434
435 /* we don't support huge pages yet */
436
437 build_get_ptep(&p, GPR_K0, GPR_K1);
438 build_update_entries(&p, GPR_K0, GPR_K1);
439 build_tlb_write_entry(&p, &l, &r, tlb_random);
440 #endif
441
442 preempt_enable();
443
444 /* Get the VCPU pointer from the VCPU scratch register again */
445 UASM_i_MFC0(&p, GPR_K1, scratch_vcpu[0], scratch_vcpu[1]);
446
447 /* Restore the guest's k0/k1 registers */
448 UASM_i_LW(&p, GPR_K0, offsetof(struct kvm_vcpu, arch.gprs[GPR_K0]), GPR_K1);
449 uasm_i_ehb(&p);
450 UASM_i_MFC0(&p, GPR_K1, scratch_tmp[0], scratch_tmp[1]);
451
452 /* Jump to guest */
453 uasm_i_eret(&p);
454
455 return p;
456 }
457
458 /**
459 * kvm_mips_build_exception() - Assemble first level guest exception handler.
460 * @addr: Address to start writing code.
461 * @handler: Address of common handler (within range of @addr).
462 *
463 * Assemble exception vector code for guest execution. The generated vector will
464 * branch to the common exception handler generated by kvm_mips_build_exit().
465 *
466 * Returns: Next address after end of written function.
467 */
kvm_mips_build_exception(void * addr,void * handler)468 void *kvm_mips_build_exception(void *addr, void *handler)
469 {
470 u32 *p = addr;
471 struct uasm_label labels[2];
472 struct uasm_reloc relocs[2];
473 struct uasm_label *l = labels;
474 struct uasm_reloc *r = relocs;
475
476 memset(labels, 0, sizeof(labels));
477 memset(relocs, 0, sizeof(relocs));
478
479 /* Save guest k1 into scratch register */
480 UASM_i_MTC0(&p, GPR_K1, scratch_tmp[0], scratch_tmp[1]);
481
482 /* Get the VCPU pointer from the VCPU scratch register */
483 UASM_i_MFC0(&p, GPR_K1, scratch_vcpu[0], scratch_vcpu[1]);
484 UASM_i_ADDIU(&p, GPR_K1, GPR_K1, offsetof(struct kvm_vcpu, arch));
485
486 /* Save guest k0 into VCPU structure */
487 UASM_i_SW(&p, GPR_K0, offsetof(struct kvm_vcpu_arch, gprs[GPR_K0]), GPR_K1);
488
489 /* Branch to the common handler */
490 uasm_il_b(&p, &r, label_exit_common);
491 uasm_i_nop(&p);
492
493 uasm_l_exit_common(&l, handler);
494 uasm_resolve_relocs(relocs, labels);
495
496 return p;
497 }
498
499 /**
500 * kvm_mips_build_exit() - Assemble common guest exit handler.
501 * @addr: Address to start writing code.
502 *
503 * Assemble the generic guest exit handling code. This is called by the
504 * exception vectors (generated by kvm_mips_build_exception()), and calls
505 * kvm_mips_handle_exit(), then either resumes the guest or returns to the host
506 * depending on the return value.
507 *
508 * Returns: Next address after end of written function.
509 */
kvm_mips_build_exit(void * addr)510 void *kvm_mips_build_exit(void *addr)
511 {
512 u32 *p = addr;
513 unsigned int i;
514 struct uasm_label labels[3];
515 struct uasm_reloc relocs[3];
516 struct uasm_label *l = labels;
517 struct uasm_reloc *r = relocs;
518
519 memset(labels, 0, sizeof(labels));
520 memset(relocs, 0, sizeof(relocs));
521
522 /*
523 * Generic Guest exception handler. We end up here when the guest
524 * does something that causes a trap to kernel mode.
525 *
526 * Both k0/k1 registers will have already been saved (k0 into the vcpu
527 * structure, and k1 into the scratch_tmp register).
528 *
529 * The k1 register will already contain the kvm_vcpu_arch pointer.
530 */
531
532 /* Start saving Guest context to VCPU */
533 for (i = 0; i < 32; ++i) {
534 /* Guest k0/k1 saved later */
535 if (i == GPR_K0 || i == GPR_K1)
536 continue;
537 UASM_i_SW(&p, i, offsetof(struct kvm_vcpu_arch, gprs[i]), GPR_K1);
538 }
539
540 #ifndef CONFIG_CPU_MIPSR6
541 /* We need to save hi/lo and restore them on the way out */
542 uasm_i_mfhi(&p, GPR_T0);
543 UASM_i_SW(&p, GPR_T0, offsetof(struct kvm_vcpu_arch, hi), GPR_K1);
544
545 uasm_i_mflo(&p, GPR_T0);
546 UASM_i_SW(&p, GPR_T0, offsetof(struct kvm_vcpu_arch, lo), GPR_K1);
547 #endif
548
549 /* Finally save guest k1 to VCPU */
550 uasm_i_ehb(&p);
551 UASM_i_MFC0(&p, GPR_T0, scratch_tmp[0], scratch_tmp[1]);
552 UASM_i_SW(&p, GPR_T0, offsetof(struct kvm_vcpu_arch, gprs[GPR_K1]), GPR_K1);
553
554 /* Now that context has been saved, we can use other registers */
555
556 /* Restore vcpu */
557 UASM_i_MFC0(&p, GPR_S0, scratch_vcpu[0], scratch_vcpu[1]);
558
559 /*
560 * Save Host level EPC, BadVaddr and Cause to VCPU, useful to process
561 * the exception
562 */
563 UASM_i_MFC0(&p, GPR_K0, C0_EPC);
564 UASM_i_SW(&p, GPR_K0, offsetof(struct kvm_vcpu_arch, pc), GPR_K1);
565
566 UASM_i_MFC0(&p, GPR_K0, C0_BADVADDR);
567 UASM_i_SW(&p, GPR_K0, offsetof(struct kvm_vcpu_arch, host_cp0_badvaddr),
568 GPR_K1);
569
570 uasm_i_mfc0(&p, GPR_K0, C0_CAUSE);
571 uasm_i_sw(&p, GPR_K0, offsetof(struct kvm_vcpu_arch, host_cp0_cause), GPR_K1);
572
573 if (cpu_has_badinstr) {
574 uasm_i_mfc0(&p, GPR_K0, C0_BADINSTR);
575 uasm_i_sw(&p, GPR_K0, offsetof(struct kvm_vcpu_arch,
576 host_cp0_badinstr), GPR_K1);
577 }
578
579 if (cpu_has_badinstrp) {
580 uasm_i_mfc0(&p, GPR_K0, C0_BADINSTRP);
581 uasm_i_sw(&p, GPR_K0, offsetof(struct kvm_vcpu_arch,
582 host_cp0_badinstrp), GPR_K1);
583 }
584
585 /* Now restore the host state just enough to run the handlers */
586
587 /* Switch EBASE to the one used by Linux */
588 /* load up the host EBASE */
589 uasm_i_mfc0(&p, GPR_V0, C0_STATUS);
590
591 uasm_i_lui(&p, GPR_AT, ST0_BEV >> 16);
592 uasm_i_or(&p, GPR_K0, GPR_V0, GPR_AT);
593
594 uasm_i_mtc0(&p, GPR_K0, C0_STATUS);
595 uasm_i_ehb(&p);
596
597 UASM_i_LA_mostly(&p, GPR_K0, (long)&ebase);
598 UASM_i_LW(&p, GPR_K0, uasm_rel_lo((long)&ebase), GPR_K0);
599 build_set_exc_base(&p, GPR_K0);
600
601 if (raw_cpu_has_fpu) {
602 /*
603 * If FPU is enabled, save FCR31 and clear it so that later
604 * ctc1's don't trigger FPE for pending exceptions.
605 */
606 uasm_i_lui(&p, GPR_AT, ST0_CU1 >> 16);
607 uasm_i_and(&p, GPR_V1, GPR_V0, GPR_AT);
608 uasm_il_beqz(&p, &r, GPR_V1, label_fpu_1);
609 uasm_i_nop(&p);
610 uasm_i_cfc1(&p, GPR_T0, 31);
611 uasm_i_sw(&p, GPR_T0, offsetof(struct kvm_vcpu_arch, fpu.fcr31),
612 GPR_K1);
613 uasm_i_ctc1(&p, GPR_ZERO, 31);
614 uasm_l_fpu_1(&l, p);
615 }
616
617 if (cpu_has_msa) {
618 /*
619 * If MSA is enabled, save MSACSR and clear it so that later
620 * instructions don't trigger MSAFPE for pending exceptions.
621 */
622 uasm_i_mfc0(&p, GPR_T0, C0_CONFIG5);
623 uasm_i_ext(&p, GPR_T0, GPR_T0, 27, 1); /* MIPS_CONF5_MSAEN */
624 uasm_il_beqz(&p, &r, GPR_T0, label_msa_1);
625 uasm_i_nop(&p);
626 uasm_i_cfcmsa(&p, GPR_T0, MSA_CSR);
627 uasm_i_sw(&p, GPR_T0, offsetof(struct kvm_vcpu_arch, fpu.msacsr),
628 GPR_K1);
629 uasm_i_ctcmsa(&p, MSA_CSR, GPR_ZERO);
630 uasm_l_msa_1(&l, p);
631 }
632
633 /* Restore host ASID */
634 if (!cpu_has_guestid) {
635 UASM_i_LW(&p, GPR_K0, offsetof(struct kvm_vcpu_arch, host_entryhi),
636 GPR_K1);
637 UASM_i_MTC0(&p, GPR_K0, C0_ENTRYHI);
638 }
639
640 /*
641 * Set up normal Linux process pgd.
642 * This does roughly the same as TLBMISS_HANDLER_SETUP_PGD():
643 * - call tlbmiss_handler_setup_pgd(mm->pgd)
644 * - write mm->pgd into CP0_PWBase
645 */
646 UASM_i_LW(&p, GPR_A0,
647 offsetof(struct kvm_vcpu_arch, host_pgd), GPR_K1);
648 UASM_i_LA(&p, GPR_T9, (unsigned long)tlbmiss_handler_setup_pgd);
649 uasm_i_jalr(&p, GPR_RA, GPR_T9);
650 /* delay slot */
651 if (cpu_has_htw)
652 UASM_i_MTC0(&p, GPR_A0, C0_PWBASE);
653 else
654 uasm_i_nop(&p);
655
656 /* Clear GM bit so we don't enter guest mode when EXL is cleared */
657 uasm_i_mfc0(&p, GPR_K0, C0_GUESTCTL0);
658 uasm_i_ins(&p, GPR_K0, GPR_ZERO, MIPS_GCTL0_GM_SHIFT, 1);
659 uasm_i_mtc0(&p, GPR_K0, C0_GUESTCTL0);
660
661 /* Save GuestCtl0 so we can access GExcCode after CPU migration */
662 uasm_i_sw(&p, GPR_K0,
663 offsetof(struct kvm_vcpu_arch, host_cp0_guestctl0), GPR_K1);
664
665 if (cpu_has_guestid) {
666 /*
667 * Clear root mode GuestID, so that root TLB operations use the
668 * root GuestID in the root TLB.
669 */
670 uasm_i_mfc0(&p, GPR_T0, C0_GUESTCTL1);
671 /* Set GuestCtl1.RID = MIPS_GCTL1_ROOT_GUESTID (i.e. 0) */
672 uasm_i_ins(&p, GPR_T0, GPR_ZERO, MIPS_GCTL1_RID_SHIFT,
673 MIPS_GCTL1_RID_WIDTH);
674 uasm_i_mtc0(&p, GPR_T0, C0_GUESTCTL1);
675 }
676
677 /* Now that the new EBASE has been loaded, unset BEV and KSU_USER */
678 uasm_i_addiu(&p, GPR_AT, GPR_ZERO, ~(ST0_EXL | KSU_USER | ST0_IE));
679 uasm_i_and(&p, GPR_V0, GPR_V0, GPR_AT);
680 uasm_i_lui(&p, GPR_AT, ST0_CU0 >> 16);
681 uasm_i_or(&p, GPR_V0, GPR_V0, GPR_AT);
682 #ifdef CONFIG_64BIT
683 uasm_i_ori(&p, GPR_V0, GPR_V0, ST0_SX | ST0_UX);
684 #endif
685 uasm_i_mtc0(&p, GPR_V0, C0_STATUS);
686 uasm_i_ehb(&p);
687
688 /* Load up host GPR_GP */
689 UASM_i_LW(&p, GPR_GP, offsetof(struct kvm_vcpu_arch, host_gp), GPR_K1);
690
691 /* Need a stack before we can jump to "C" */
692 UASM_i_LW(&p, GPR_SP, offsetof(struct kvm_vcpu_arch, host_stack), GPR_K1);
693
694 /* Saved host state */
695 UASM_i_ADDIU(&p, GPR_SP, GPR_SP, -(int)sizeof(struct pt_regs));
696
697 /*
698 * XXXKYMA do we need to load the host ASID, maybe not because the
699 * kernel entries are marked GLOBAL, need to verify
700 */
701
702 /* Restore host scratch registers, as we'll have clobbered them */
703 kvm_mips_build_restore_scratch(&p, GPR_K0, GPR_SP);
704
705 /* Restore RDHWR access */
706 UASM_i_LA_mostly(&p, GPR_K0, (long)&hwrena);
707 uasm_i_lw(&p, GPR_K0, uasm_rel_lo((long)&hwrena), GPR_K0);
708 uasm_i_mtc0(&p, GPR_K0, C0_HWRENA);
709
710 /* Jump to handler */
711 /*
712 * XXXKYMA: not sure if this is safe, how large is the stack??
713 * Now jump to the kvm_mips_handle_exit() to see if we can deal
714 * with this in the kernel
715 */
716 uasm_i_move(&p, GPR_A0, GPR_S0);
717 UASM_i_LA(&p, GPR_T9, (unsigned long)kvm_mips_handle_exit);
718 uasm_i_jalr(&p, GPR_RA, GPR_T9);
719 UASM_i_ADDIU(&p, GPR_SP, GPR_SP, -CALLFRAME_SIZ);
720
721 uasm_resolve_relocs(relocs, labels);
722
723 p = kvm_mips_build_ret_from_exit(p);
724
725 return p;
726 }
727
728 /**
729 * kvm_mips_build_ret_from_exit() - Assemble guest exit return handler.
730 * @addr: Address to start writing code.
731 *
732 * Assemble the code to handle the return from kvm_mips_handle_exit(), either
733 * resuming the guest or returning to the host depending on the return value.
734 *
735 * Returns: Next address after end of written function.
736 */
kvm_mips_build_ret_from_exit(void * addr)737 static void *kvm_mips_build_ret_from_exit(void *addr)
738 {
739 u32 *p = addr;
740 struct uasm_label labels[2];
741 struct uasm_reloc relocs[2];
742 struct uasm_label *l = labels;
743 struct uasm_reloc *r = relocs;
744
745 memset(labels, 0, sizeof(labels));
746 memset(relocs, 0, sizeof(relocs));
747
748 /* Return from handler Make sure interrupts are disabled */
749 uasm_i_di(&p, GPR_ZERO);
750 uasm_i_ehb(&p);
751
752 /*
753 * XXXKYMA: k0/k1 could have been blown away if we processed
754 * an exception while we were handling the exception from the
755 * guest, reload k1
756 */
757
758 uasm_i_move(&p, GPR_K1, GPR_S0);
759 UASM_i_ADDIU(&p, GPR_K1, GPR_K1, offsetof(struct kvm_vcpu, arch));
760
761 /*
762 * Check return value, should tell us if we are returning to the
763 * host (handle I/O etc)or resuming the guest
764 */
765 uasm_i_andi(&p, GPR_T0, GPR_V0, RESUME_HOST);
766 uasm_il_bnez(&p, &r, GPR_T0, label_return_to_host);
767 uasm_i_nop(&p);
768
769 p = kvm_mips_build_ret_to_guest(p);
770
771 uasm_l_return_to_host(&l, p);
772 p = kvm_mips_build_ret_to_host(p);
773
774 uasm_resolve_relocs(relocs, labels);
775
776 return p;
777 }
778
779 /**
780 * kvm_mips_build_ret_to_guest() - Assemble code to return to the guest.
781 * @addr: Address to start writing code.
782 *
783 * Assemble the code to handle return from the guest exit handler
784 * (kvm_mips_handle_exit()) back to the guest.
785 *
786 * Returns: Next address after end of written function.
787 */
kvm_mips_build_ret_to_guest(void * addr)788 static void *kvm_mips_build_ret_to_guest(void *addr)
789 {
790 u32 *p = addr;
791
792 /* Put the saved pointer to vcpu (s0) back into the scratch register */
793 UASM_i_MTC0(&p, GPR_S0, scratch_vcpu[0], scratch_vcpu[1]);
794
795 /* Load up the Guest EBASE to minimize the window where BEV is set */
796 UASM_i_LW(&p, GPR_T0, offsetof(struct kvm_vcpu_arch, guest_ebase), GPR_K1);
797
798 /* Switch EBASE back to the one used by KVM */
799 uasm_i_mfc0(&p, GPR_V1, C0_STATUS);
800 uasm_i_lui(&p, GPR_AT, ST0_BEV >> 16);
801 uasm_i_or(&p, GPR_K0, GPR_V1, GPR_AT);
802 uasm_i_mtc0(&p, GPR_K0, C0_STATUS);
803 uasm_i_ehb(&p);
804 build_set_exc_base(&p, GPR_T0);
805
806 /* Setup status register for running guest in UM */
807 uasm_i_ori(&p, GPR_V1, GPR_V1, ST0_EXL | KSU_USER | ST0_IE);
808 UASM_i_LA(&p, GPR_AT, ~(ST0_CU0 | ST0_MX | ST0_SX | ST0_UX));
809 uasm_i_and(&p, GPR_V1, GPR_V1, GPR_AT);
810 uasm_i_mtc0(&p, GPR_V1, C0_STATUS);
811 uasm_i_ehb(&p);
812
813 p = kvm_mips_build_enter_guest(p);
814
815 return p;
816 }
817
818 /**
819 * kvm_mips_build_ret_to_host() - Assemble code to return to the host.
820 * @addr: Address to start writing code.
821 *
822 * Assemble the code to handle return from the guest exit handler
823 * (kvm_mips_handle_exit()) back to the host, i.e. to the caller of the vcpu_run
824 * function generated by kvm_mips_build_vcpu_run().
825 *
826 * Returns: Next address after end of written function.
827 */
kvm_mips_build_ret_to_host(void * addr)828 static void *kvm_mips_build_ret_to_host(void *addr)
829 {
830 u32 *p = addr;
831 unsigned int i;
832
833 /* EBASE is already pointing to Linux */
834 UASM_i_LW(&p, GPR_K1, offsetof(struct kvm_vcpu_arch, host_stack), GPR_K1);
835 UASM_i_ADDIU(&p, GPR_K1, GPR_K1, -(int)sizeof(struct pt_regs));
836
837 /*
838 * r2/v0 is the return code, shift it down by 2 (arithmetic)
839 * to recover the err code
840 */
841 uasm_i_sra(&p, GPR_K0, GPR_V0, 2);
842 uasm_i_move(&p, GPR_V0, GPR_K0);
843
844 /* Load context saved on the host stack */
845 for (i = 16; i < 31; ++i) {
846 if (i == 24)
847 i = 28;
848 UASM_i_LW(&p, i, offsetof(struct pt_regs, regs[i]), GPR_K1);
849 }
850
851 /* Restore RDHWR access */
852 UASM_i_LA_mostly(&p, GPR_K0, (long)&hwrena);
853 uasm_i_lw(&p, GPR_K0, uasm_rel_lo((long)&hwrena), GPR_K0);
854 uasm_i_mtc0(&p, GPR_K0, C0_HWRENA);
855
856 /* Restore GPR_RA, which is the address we will return to */
857 UASM_i_LW(&p, GPR_RA, offsetof(struct pt_regs, regs[GPR_RA]), GPR_K1);
858 uasm_i_jr(&p, GPR_RA);
859 uasm_i_nop(&p);
860
861 return p;
862 }
863
864