arch/mips/kvm/vz.c:391:10: warning: variable 'freeze_time' set but not used

From: kernel test robot
Date: Sun Jun 20 2021 - 14:23:11 EST

Hi Thomas,

First bad commit (maybe != root cause):

tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head: 913ec3c22ef425d63dd0bc81fb008ce7f9bcb07b
commit: 45c7e8af4a5e3f0bea4ac209eea34118dd57ac64 MIPS: Remove KVM_TE support
date: 3 months ago
config: mips-randconfig-r002-20210620 (attached as .config)
compiler: mipsel-linux-gcc (GCC) 9.3.0
reproduce (this is a W=1 build):
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=45c7e8af4a5e3f0bea4ac209eea34118dd57ac64
git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
git fetch --no-tags linus master
git checkout 45c7e8af4a5e3f0bea4ac209eea34118dd57ac64
# save the attached .config to linux build tree
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross ARCH=mips

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@xxxxxxxxx>

All warnings (new ones prefixed by >>):

arch/mips/kvm/vz.c: In function '_kvm_vz_restore_htimer':
>> arch/mips/kvm/vz.c:391:10: warning: variable 'freeze_time' set but not used [-Wunused-but-set-variable]
391 | ktime_t freeze_time;
| ^~~~~~~~~~~
--
arch/mips/kvm/vz.c:471: warning: Function parameter or member 'out_compare' not described in '_kvm_vz_save_htimer'
arch/mips/kvm/vz.c:471: warning: Function parameter or member 'out_cause' not described in '_kvm_vz_save_htimer'
arch/mips/kvm/vz.c:471: warning: Excess function parameter 'compare' description in '_kvm_vz_save_htimer'
arch/mips/kvm/vz.c:471: warning: Excess function parameter 'cause' description in '_kvm_vz_save_htimer'
>> arch/mips/kvm/vz.c:1552: warning: expecting prototype for kvm_trap_vz_handle_cop_unusuable(). Prototype was for kvm_trap_vz_handle_cop_unusable() instead


vim +/freeze_time +391 arch/mips/kvm/vz.c

c992a4f6a9b0a3 James Hogan 2017-03-14 377
c992a4f6a9b0a3 James Hogan 2017-03-14 378 /**
f4474d50c7d483 James Hogan 2017-03-14 379 * _kvm_vz_restore_htimer() - Restore hard timer state.
f4474d50c7d483 James Hogan 2017-03-14 380 * @vcpu: Virtual CPU.
f4474d50c7d483 James Hogan 2017-03-14 381 * @compare: CP0_Compare register value, restored by caller.
f4474d50c7d483 James Hogan 2017-03-14 382 * @cause: CP0_Cause register to restore.
f4474d50c7d483 James Hogan 2017-03-14 383 *
f4474d50c7d483 James Hogan 2017-03-14 384 * Restore hard timer Guest.Count & Guest.Cause taking care to preserve the
f4474d50c7d483 James Hogan 2017-03-14 385 * value of Guest.CP0_Cause.TI while restoring Guest.CP0_Cause.
f4474d50c7d483 James Hogan 2017-03-14 386 */
f4474d50c7d483 James Hogan 2017-03-14 387 static void _kvm_vz_restore_htimer(struct kvm_vcpu *vcpu,
f4474d50c7d483 James Hogan 2017-03-14 388 u32 compare, u32 cause)
f4474d50c7d483 James Hogan 2017-03-14 389 {
f4474d50c7d483 James Hogan 2017-03-14 390 u32 start_count, after_count;
f4474d50c7d483 James Hogan 2017-03-14 @391 ktime_t freeze_time;
f4474d50c7d483 James Hogan 2017-03-14 392 unsigned long flags;
f4474d50c7d483 James Hogan 2017-03-14 393
f4474d50c7d483 James Hogan 2017-03-14 394 /*
f4474d50c7d483 James Hogan 2017-03-14 395 * Freeze the soft-timer and sync the guest CP0_Count with it. We do
f4474d50c7d483 James Hogan 2017-03-14 396 * this with interrupts disabled to avoid latency.
f4474d50c7d483 James Hogan 2017-03-14 397 */
f4474d50c7d483 James Hogan 2017-03-14 398 local_irq_save(flags);
f4474d50c7d483 James Hogan 2017-03-14 399 freeze_time = kvm_mips_freeze_hrtimer(vcpu, &start_count);
f4474d50c7d483 James Hogan 2017-03-14 400 write_c0_gtoffset(start_count - read_c0_count());
f4474d50c7d483 James Hogan 2017-03-14 401 local_irq_restore(flags);
f4474d50c7d483 James Hogan 2017-03-14 402
f4474d50c7d483 James Hogan 2017-03-14 403 /* restore guest CP0_Cause, as TI may already be set */
f4474d50c7d483 James Hogan 2017-03-14 404 back_to_back_c0_hazard();
f4474d50c7d483 James Hogan 2017-03-14 405 write_gc0_cause(cause);
f4474d50c7d483 James Hogan 2017-03-14 406
f4474d50c7d483 James Hogan 2017-03-14 407 /*
f4474d50c7d483 James Hogan 2017-03-14 408 * The above sequence isn't atomic and would result in lost timer
f4474d50c7d483 James Hogan 2017-03-14 409 * interrupts if we're not careful. Detect if a timer interrupt is due
f4474d50c7d483 James Hogan 2017-03-14 410 * and assert it.
f4474d50c7d483 James Hogan 2017-03-14 411 */
f4474d50c7d483 James Hogan 2017-03-14 412 back_to_back_c0_hazard();
f4474d50c7d483 James Hogan 2017-03-14 413 after_count = read_gc0_count();
f4474d50c7d483 James Hogan 2017-03-14 414 if (after_count - start_count > compare - start_count - 1)
f4474d50c7d483 James Hogan 2017-03-14 415 kvm_vz_queue_irq(vcpu, MIPS_EXC_INT_TIMER);
f4474d50c7d483 James Hogan 2017-03-14 416 }
f4474d50c7d483 James Hogan 2017-03-14 417
f4474d50c7d483 James Hogan 2017-03-14 418 /**
f4474d50c7d483 James Hogan 2017-03-14 419 * kvm_vz_restore_timer() - Restore timer state.
c992a4f6a9b0a3 James Hogan 2017-03-14 420 * @vcpu: Virtual CPU.
c992a4f6a9b0a3 James Hogan 2017-03-14 421 *
c992a4f6a9b0a3 James Hogan 2017-03-14 422 * Restore soft timer state from saved context.
c992a4f6a9b0a3 James Hogan 2017-03-14 423 */
c992a4f6a9b0a3 James Hogan 2017-03-14 424 static void kvm_vz_restore_timer(struct kvm_vcpu *vcpu)
c992a4f6a9b0a3 James Hogan 2017-03-14 425 {
c992a4f6a9b0a3 James Hogan 2017-03-14 426 struct mips_coproc *cop0 = vcpu->arch.cop0;
c992a4f6a9b0a3 James Hogan 2017-03-14 427 u32 cause, compare;
c992a4f6a9b0a3 James Hogan 2017-03-14 428
c992a4f6a9b0a3 James Hogan 2017-03-14 429 compare = kvm_read_sw_gc0_compare(cop0);
c992a4f6a9b0a3 James Hogan 2017-03-14 430 cause = kvm_read_sw_gc0_cause(cop0);
c992a4f6a9b0a3 James Hogan 2017-03-14 431
c992a4f6a9b0a3 James Hogan 2017-03-14 432 write_gc0_compare(compare);
c992a4f6a9b0a3 James Hogan 2017-03-14 433 _kvm_vz_restore_stimer(vcpu, compare, cause);
c992a4f6a9b0a3 James Hogan 2017-03-14 434 }
c992a4f6a9b0a3 James Hogan 2017-03-14 435
f4474d50c7d483 James Hogan 2017-03-14 436 /**
f4474d50c7d483 James Hogan 2017-03-14 437 * kvm_vz_acquire_htimer() - Switch to hard timer state.
f4474d50c7d483 James Hogan 2017-03-14 438 * @vcpu: Virtual CPU.
f4474d50c7d483 James Hogan 2017-03-14 439 *
f4474d50c7d483 James Hogan 2017-03-14 440 * Restore hard timer state on top of existing soft timer state if possible.
f4474d50c7d483 James Hogan 2017-03-14 441 *
f4474d50c7d483 James Hogan 2017-03-14 442 * Since hard timer won't remain active over preemption, preemption should be
f4474d50c7d483 James Hogan 2017-03-14 443 * disabled by the caller.
f4474d50c7d483 James Hogan 2017-03-14 444 */
f4474d50c7d483 James Hogan 2017-03-14 445 void kvm_vz_acquire_htimer(struct kvm_vcpu *vcpu)
f4474d50c7d483 James Hogan 2017-03-14 446 {
f4474d50c7d483 James Hogan 2017-03-14 447 u32 gctl0;
f4474d50c7d483 James Hogan 2017-03-14 448
f4474d50c7d483 James Hogan 2017-03-14 449 gctl0 = read_c0_guestctl0();
f4474d50c7d483 James Hogan 2017-03-14 450 if (!(gctl0 & MIPS_GCTL0_GT) && kvm_vz_should_use_htimer(vcpu)) {
f4474d50c7d483 James Hogan 2017-03-14 451 /* enable guest access to hard timer */
f4474d50c7d483 James Hogan 2017-03-14 452 write_c0_guestctl0(gctl0 | MIPS_GCTL0_GT);
f4474d50c7d483 James Hogan 2017-03-14 453
f4474d50c7d483 James Hogan 2017-03-14 454 _kvm_vz_restore_htimer(vcpu, read_gc0_compare(),
f4474d50c7d483 James Hogan 2017-03-14 455 read_gc0_cause());
f4474d50c7d483 James Hogan 2017-03-14 456 }
f4474d50c7d483 James Hogan 2017-03-14 457 }
f4474d50c7d483 James Hogan 2017-03-14 458
f4474d50c7d483 James Hogan 2017-03-14 459 /**
f4474d50c7d483 James Hogan 2017-03-14 460 * _kvm_vz_save_htimer() - Switch to software emulation of guest timer.
f4474d50c7d483 James Hogan 2017-03-14 461 * @vcpu: Virtual CPU.
f4474d50c7d483 James Hogan 2017-03-14 462 * @compare: Pointer to write compare value to.
f4474d50c7d483 James Hogan 2017-03-14 463 * @cause: Pointer to write cause value to.
f4474d50c7d483 James Hogan 2017-03-14 464 *
f4474d50c7d483 James Hogan 2017-03-14 465 * Save VZ guest timer state and switch to software emulation of guest CP0
f4474d50c7d483 James Hogan 2017-03-14 466 * timer. The hard timer must already be in use, so preemption should be
f4474d50c7d483 James Hogan 2017-03-14 467 * disabled.
f4474d50c7d483 James Hogan 2017-03-14 468 */
f4474d50c7d483 James Hogan 2017-03-14 469 static void _kvm_vz_save_htimer(struct kvm_vcpu *vcpu,
f4474d50c7d483 James Hogan 2017-03-14 470 u32 *out_compare, u32 *out_cause)
f4474d50c7d483 James Hogan 2017-03-14 @471 {
f4474d50c7d483 James Hogan 2017-03-14 472 u32 cause, compare, before_count, end_count;
f4474d50c7d483 James Hogan 2017-03-14 473 ktime_t before_time;
f4474d50c7d483 James Hogan 2017-03-14 474
f4474d50c7d483 James Hogan 2017-03-14 475 compare = read_gc0_compare();
f4474d50c7d483 James Hogan 2017-03-14 476 *out_compare = compare;
f4474d50c7d483 James Hogan 2017-03-14 477
f4474d50c7d483 James Hogan 2017-03-14 478 before_time = ktime_get();
f4474d50c7d483 James Hogan 2017-03-14 479
f4474d50c7d483 James Hogan 2017-03-14 480 /*
f4474d50c7d483 James Hogan 2017-03-14 481 * Record the CP0_Count *prior* to saving CP0_Cause, so we have a time
f4474d50c7d483 James Hogan 2017-03-14 482 * at which no pending timer interrupt is missing.
f4474d50c7d483 James Hogan 2017-03-14 483 */
f4474d50c7d483 James Hogan 2017-03-14 484 before_count = read_gc0_count();
f4474d50c7d483 James Hogan 2017-03-14 485 back_to_back_c0_hazard();
f4474d50c7d483 James Hogan 2017-03-14 486 cause = read_gc0_cause();
f4474d50c7d483 James Hogan 2017-03-14 487 *out_cause = cause;
f4474d50c7d483 James Hogan 2017-03-14 488
f4474d50c7d483 James Hogan 2017-03-14 489 /*
f4474d50c7d483 James Hogan 2017-03-14 490 * Record a final CP0_Count which we will transfer to the soft-timer.
f4474d50c7d483 James Hogan 2017-03-14 491 * This is recorded *after* saving CP0_Cause, so we don't get any timer
f4474d50c7d483 James Hogan 2017-03-14 492 * interrupts from just after the final CP0_Count point.
f4474d50c7d483 James Hogan 2017-03-14 493 */
f4474d50c7d483 James Hogan 2017-03-14 494 back_to_back_c0_hazard();
f4474d50c7d483 James Hogan 2017-03-14 495 end_count = read_gc0_count();
f4474d50c7d483 James Hogan 2017-03-14 496
f4474d50c7d483 James Hogan 2017-03-14 497 /*
f4474d50c7d483 James Hogan 2017-03-14 498 * The above sequence isn't atomic, so we could miss a timer interrupt
f4474d50c7d483 James Hogan 2017-03-14 499 * between reading CP0_Cause and end_count. Detect and record any timer
f4474d50c7d483 James Hogan 2017-03-14 500 * interrupt due between before_count and end_count.
f4474d50c7d483 James Hogan 2017-03-14 501 */
f4474d50c7d483 James Hogan 2017-03-14 502 if (end_count - before_count > compare - before_count - 1)
f4474d50c7d483 James Hogan 2017-03-14 503 kvm_vz_queue_irq(vcpu, MIPS_EXC_INT_TIMER);
f4474d50c7d483 James Hogan 2017-03-14 504
f4474d50c7d483 James Hogan 2017-03-14 505 /*
f4474d50c7d483 James Hogan 2017-03-14 506 * Restore soft-timer, ignoring a small amount of negative drift due to
f4474d50c7d483 James Hogan 2017-03-14 507 * delay between freeze_hrtimer and setting CP0_GTOffset.
f4474d50c7d483 James Hogan 2017-03-14 508 */
f4474d50c7d483 James Hogan 2017-03-14 509 kvm_mips_restore_hrtimer(vcpu, before_time, end_count, -0x10000);
f4474d50c7d483 James Hogan 2017-03-14 510 }
f4474d50c7d483 James Hogan 2017-03-14 511

:::::: The code at line 391 was first introduced by commit
:::::: f4474d50c7d483dd4432d5b0891b0bb9ad0eefc9 KVM: MIPS/VZ: Support hardware guest timer

:::::: TO: James Hogan <james.hogan@xxxxxxxxxx>
:::::: CC: James Hogan <james.hogan@xxxxxxxxxx>

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@xxxxxxxxxxxx

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