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... 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(a)intel.com&gt; All warnings (new ones prefixed by >>): arch/mips/kvm/vz.c: In function '_kvm_vz_restore_htimer': 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' 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(a)imgtec.com&gt; :::::: CC: James Hogan <james.hogan(a)imgtec.com&gt; --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org