diff options
| -rw-r--r-- | arch/mips/include/asm/kvm_host.h | 14 | ||||
| -rw-r--r-- | arch/mips/kvm/emulate.c | 81 | ||||
| -rw-r--r-- | arch/mips/kvm/mips.c | 6 | ||||
| -rw-r--r-- | arch/mips/kvm/vz.c | 197 |
4 files changed, 287 insertions, 11 deletions
diff --git a/arch/mips/include/asm/kvm_host.h b/arch/mips/include/asm/kvm_host.h index a662a80..5c518c1 100644 --- a/arch/mips/include/asm/kvm_host.h +++ b/arch/mips/include/asm/kvm_host.h @@ -1068,6 +1068,20 @@ void kvm_mips_count_enable_cause(struct kvm_vcpu *vcpu); void kvm_mips_count_disable_cause(struct kvm_vcpu *vcpu); enum hrtimer_restart kvm_mips_count_timeout(struct kvm_vcpu *vcpu); +/* fairly internal functions requiring some care to use */ +int kvm_mips_count_disabled(struct kvm_vcpu *vcpu); +ktime_t kvm_mips_freeze_hrtimer(struct kvm_vcpu *vcpu, u32 *count); +int kvm_mips_restore_hrtimer(struct kvm_vcpu *vcpu, ktime_t before, + u32 count, int min_drift); + +#ifdef CONFIG_KVM_MIPS_VZ +void kvm_vz_acquire_htimer(struct kvm_vcpu *vcpu); +void kvm_vz_lose_htimer(struct kvm_vcpu *vcpu); +#else +static inline void kvm_vz_acquire_htimer(struct kvm_vcpu *vcpu) {} +static inline void kvm_vz_lose_htimer(struct kvm_vcpu *vcpu) {} +#endif + enum emulation_result kvm_mips_check_privilege(u32 cause, u32 *opc, struct kvm_run *run, diff --git a/arch/mips/kvm/emulate.c b/arch/mips/kvm/emulate.c index bb04492..2070864 100644 --- a/arch/mips/kvm/emulate.c +++ b/arch/mips/kvm/emulate.c @@ -308,7 +308,7 @@ int kvm_get_badinstrp(u32 *opc, struct kvm_vcpu *vcpu, u32 *out) * CP0_Cause.DC bit or the count_ctl.DC bit. * 0 otherwise (in which case CP0_Count timer is running). */ -static inline int kvm_mips_count_disabled(struct kvm_vcpu *vcpu) +int kvm_mips_count_disabled(struct kvm_vcpu *vcpu) { struct mips_coproc *cop0 = vcpu->arch.cop0; @@ -467,7 +467,7 @@ u32 kvm_mips_read_count(struct kvm_vcpu *vcpu) * * Returns: The ktime at the point of freeze. */ -static ktime_t kvm_mips_freeze_hrtimer(struct kvm_vcpu *vcpu, u32 *count) +ktime_t kvm_mips_freeze_hrtimer(struct kvm_vcpu *vcpu, u32 *count) { ktime_t now; @@ -517,6 +517,82 @@ static void kvm_mips_resume_hrtimer(struct kvm_vcpu *vcpu, } /** + * kvm_mips_restore_hrtimer() - Restore hrtimer after a gap, updating expiry. + * @vcpu: Virtual CPU. + * @before: Time before Count was saved, lower bound of drift calculation. + * @count: CP0_Count at point of restore. + * @min_drift: Minimum amount of drift permitted before correction. + * Must be <= 0. + * + * Restores the timer from a particular @count, accounting for drift. This can + * be used in conjunction with kvm_mips_freeze_timer() when a hardware timer is + * to be used for a period of time, but the exact ktime corresponding to the + * final Count that must be restored is not known. + * + * It is gauranteed that a timer interrupt immediately after restore will be + * handled, but not if CP0_Compare is exactly at @count. That case should + * already be handled when the hardware timer state is saved. + * + * Assumes !kvm_mips_count_disabled(@vcpu) (guest CP0_Count timer is not + * stopped). + * + * Returns: Amount of correction to count_bias due to drift. + */ +int kvm_mips_restore_hrtimer(struct kvm_vcpu *vcpu, ktime_t before, + u32 count, int min_drift) +{ + ktime_t now, count_time; + u32 now_count, before_count; + u64 delta; + int drift, ret = 0; + + /* Calculate expected count at before */ + before_count = vcpu->arch.count_bias + + kvm_mips_ktime_to_count(vcpu, before); + + /* + * Detect significantly negative drift, where count is lower than + * expected. Some negative drift is expected when hardware counter is + * set after kvm_mips_freeze_timer(), and it is harmless to allow the + * time to jump forwards a little, within reason. If the drift is too + * significant, adjust the bias to avoid a big Guest.CP0_Count jump. + */ + drift = count - before_count; + if (drift < min_drift) { + count_time = before; + vcpu->arch.count_bias += drift; + ret = drift; + goto resume; + } + + /* Calculate expected count right now */ + now = ktime_get(); + now_count = vcpu->arch.count_bias + kvm_mips_ktime_to_count(vcpu, now); + + /* + * Detect positive drift, where count is higher than expected, and + * adjust the bias to avoid guest time going backwards. + */ + drift = count - now_count; + if (drift > 0) { + count_time = now; + vcpu->arch.count_bias += drift; + ret = drift; + goto resume; + } + + /* Subtract nanosecond delta to find ktime when count was read */ + delta = (u64)(u32)(now_count - count); + delta = div_u64(delta * NSEC_PER_SEC, vcpu->arch.count_hz); + count_time = ktime_sub_ns(now, delta); + +resume: + /* Resume using the calculated ktime */ + kvm_mips_resume_hrtimer(vcpu, count_time, count); + return ret; +} + +/** * kvm_mips_write_count() - Modify the count and update timer. * @vcpu: Virtual CPU. * @count: Guest CP0_Count value to set. @@ -897,6 +973,7 @@ enum emulation_result kvm_mips_emul_wait(struct kvm_vcpu *vcpu) ++vcpu->stat.wait_exits; trace_kvm_exit(vcpu, KVM_TRACE_EXIT_WAIT); if (!vcpu->arch.pending_exceptions) { + kvm_vz_lose_htimer(vcpu); vcpu->arch.wait = 1; kvm_vcpu_block(vcpu); diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c index 1bb5d01..e8ddb12 100644 --- a/arch/mips/kvm/mips.c +++ b/arch/mips/kvm/mips.c @@ -1094,7 +1094,8 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) int kvm_cpu_has_pending_timer(struct kvm_vcpu *vcpu) { - return kvm_mips_pending_timer(vcpu); + return kvm_mips_pending_timer(vcpu) || + kvm_read_c0_guest_cause(vcpu->arch.cop0) & C_TI; } int kvm_arch_vcpu_dump_regs(struct kvm_vcpu *vcpu) @@ -1382,6 +1383,9 @@ int kvm_mips_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu) skip_emul: local_irq_disable(); + if (ret == RESUME_GUEST) + kvm_vz_acquire_htimer(vcpu); + if (er == EMULATE_DONE && !(ret & RESUME_HOST)) kvm_mips_deliver_interrupts(vcpu, cause); diff --git a/arch/mips/kvm/vz.c b/arch/mips/kvm/vz.c index cbc6850..44dad9a 100644 --- a/arch/mips/kvm/vz.c +++ b/arch/mips/kvm/vz.c @@ -354,12 +354,37 @@ static int kvm_vz_irq_clear_cb(struct kvm_vcpu *vcpu, unsigned int priority, */ /** + * kvm_vz_should_use_htimer() - Find whether to use the VZ hard guest timer. + * @vcpu: Virtual CPU. + * + * Returns: true if the VZ GTOffset & real guest CP0_Count should be used + * instead of software emulation of guest timer. + * false otherwise. + */ +static bool kvm_vz_should_use_htimer(struct kvm_vcpu *vcpu) +{ + if (kvm_mips_count_disabled(vcpu)) + return false; + + /* Chosen frequency must match real frequency */ + if (mips_hpt_frequency != vcpu->arch.count_hz) + return false; + + /* We don't support a CP0_GTOffset with fewer bits than CP0_Count */ + if (current_cpu_data.gtoffset_mask != 0xffffffff) + return false; + + return true; +} + +/** * _kvm_vz_restore_stimer() - Restore soft timer state. * @vcpu: Virtual CPU. * @compare: CP0_Compare register value, restored by caller. * @cause: CP0_Cause register to restore. * - * Restore VZ state relating to the soft timer. + * Restore VZ state relating to the soft timer. The hard timer can be enabled + * later. */ static void _kvm_vz_restore_stimer(struct kvm_vcpu *vcpu, u32 compare, u32 cause) @@ -375,7 +400,47 @@ static void _kvm_vz_restore_stimer(struct kvm_vcpu *vcpu, u32 compare, } /** - * kvm_vz_restore_timer() - Restore guest timer state. + * _kvm_vz_restore_htimer() - Restore hard timer state. + * @vcpu: Virtual CPU. + * @compare: CP0_Compare register value, restored by caller. + * @cause: CP0_Cause register to restore. + * + * Restore hard timer Guest.Count & Guest.Cause taking care to preserve the + * value of Guest.CP0_Cause.TI while restoring Guest.CP0_Cause. + */ +static void _kvm_vz_restore_htimer(struct kvm_vcpu *vcpu, + u32 compare, u32 cause) +{ + u32 start_count, after_count; + ktime_t freeze_time; + unsigned long flags; + + /* + * Freeze the soft-timer and sync the guest CP0_Count with it. We do + * this with interrupts disabled to avoid latency. + */ + local_irq_save(flags); + freeze_time = kvm_mips_freeze_hrtimer(vcpu, &start_count); + write_c0_gtoffset(start_count - read_c0_count()); + local_irq_restore(flags); + + /* restore guest CP0_Cause, as TI may already be set */ + back_to_back_c0_hazard(); + write_gc0_cause(cause); + + /* + * The above sequence isn't atomic and would result in lost timer + * interrupts if we're not careful. Detect if a timer interrupt is due + * and assert it. + */ + back_to_back_c0_hazard(); + after_count = read_gc0_count(); + if (after_count - start_count > compare - start_count - 1) + kvm_vz_queue_irq(vcpu, MIPS_EXC_INT_TIMER); +} + +/** + * kvm_vz_restore_timer() - Restore timer state. * @vcpu: Virtual CPU. * * Restore soft timer state from saved context. @@ -393,18 +458,104 @@ static void kvm_vz_restore_timer(struct kvm_vcpu *vcpu) } /** + * kvm_vz_acquire_htimer() - Switch to hard timer state. + * @vcpu: Virtual CPU. + * + * Restore hard timer state on top of existing soft timer state if possible. + * + * Since hard timer won't remain active over preemption, preemption should be + * disabled by the caller. + */ +void kvm_vz_acquire_htimer(struct kvm_vcpu *vcpu) +{ + u32 gctl0; + + gctl0 = read_c0_guestctl0(); + if (!(gctl0 & MIPS_GCTL0_GT) && kvm_vz_should_use_htimer(vcpu)) { + /* enable guest access to hard timer */ + write_c0_guestctl0(gctl0 | MIPS_GCTL0_GT); + + _kvm_vz_restore_htimer(vcpu, read_gc0_compare(), + read_gc0_cause()); + } +} + +/** + * _kvm_vz_save_htimer() - Switch to software emulation of guest timer. + * @vcpu: Virtual CPU. + * @compare: Pointer to write compare value to. + * @cause: Pointer to write cause value to. + * + * Save VZ guest timer state and switch to software emulation of guest CP0 + * timer. The hard timer must already be in use, so preemption should be + * disabled. + */ +static void _kvm_vz_save_htimer(struct kvm_vcpu *vcpu, + u32 *out_compare, u32 *out_cause) +{ + u32 cause, compare, before_count, end_count; + ktime_t before_time; + + compare = read_gc0_compare(); + *out_compare = compare; + + before_time = ktime_get(); + + /* + * Record the CP0_Count *prior* to saving CP0_Cause, so we have a time + * at which no pending timer interrupt is missing. + */ + before_count = read_gc0_count(); + back_to_back_c0_hazard(); + cause = read_gc0_cause(); + *out_cause = cause; + + /* + * Record a final CP0_Count which we will transfer to the soft-timer. + * This is recorded *after* saving CP0_Cause, so we don't get any timer + * interrupts from just after the final CP0_Count point. + */ + back_to_back_c0_hazard(); + end_count = read_gc0_count(); + + /* + * The above sequence isn't atomic, so we could miss a timer interrupt + * between reading CP0_Cause and end_count. Detect and record any timer + * interrupt due between before_count and end_count. + */ + if (end_count - before_count > compare - before_count - 1) + kvm_vz_queue_irq(vcpu, MIPS_EXC_INT_TIMER); + + /* + * Restore soft-timer, ignoring a small amount of negative drift due to + * delay between freeze_hrtimer and setting CP0_GTOffset. + */ + kvm_mips_restore_hrtimer(vcpu, before_time, end_count, -0x10000); +} + +/** * kvm_vz_save_timer() - Save guest timer state. * @vcpu: Virtual CPU. * - * Save VZ guest timer state. + * Save VZ guest timer state and switch to soft guest timer if hard timer was in + * use. */ static void kvm_vz_save_timer(struct kvm_vcpu *vcpu) { struct mips_coproc *cop0 = vcpu->arch.cop0; - u32 compare, cause; + u32 gctl0, compare, cause; - compare = read_gc0_compare(); - cause = read_gc0_cause(); + gctl0 = read_c0_guestctl0(); + if (gctl0 & MIPS_GCTL0_GT) { + /* disable guest use of hard timer */ + write_c0_guestctl0(gctl0 & ~MIPS_GCTL0_GT); + + /* save hard timer state */ + _kvm_vz_save_htimer(vcpu, &compare, &cause); + } else { + compare = read_gc0_compare(); + cause = read_gc0_cause(); + } /* save timer-related state to VCPU context */ kvm_write_sw_gc0_cause(cop0, cause); @@ -412,6 +563,32 @@ static void kvm_vz_save_timer(struct kvm_vcpu *vcpu) } /** + * kvm_vz_lose_htimer() - Ensure hard guest timer is not in use. + * @vcpu: Virtual CPU. + * + * Transfers the state of the hard guest timer to the soft guest timer, leaving + * guest state intact so it can continue to be used with the soft timer. + */ +void kvm_vz_lose_htimer(struct kvm_vcpu *vcpu) +{ + u32 gctl0, compare, cause; + + preempt_disable(); + gctl0 = read_c0_guestctl0(); + if (gctl0 & MIPS_GCTL0_GT) { + /* disable guest use of timer */ + write_c0_guestctl0(gctl0 & ~MIPS_GCTL0_GT); + + /* switch to soft timer */ + _kvm_vz_save_htimer(vcpu, &compare, &cause); + + /* leave soft timer in usable state */ + _kvm_vz_restore_stimer(vcpu, compare, cause); + } + preempt_enable(); +} + +/** * is_eva_access() - Find whether an instruction is an EVA memory accessor. * @inst: 32-bit instruction encoding. * @@ -826,6 +1003,7 @@ static enum emulation_result kvm_vz_gpsi_cop0(union mips_instruction inst, if (rd == MIPS_CP0_COUNT && sel == 0) { /* Count */ + kvm_vz_lose_htimer(vcpu); kvm_mips_write_count(vcpu, vcpu->arch.gprs[rt]); } else if (rd == MIPS_CP0_COMPARE && sel == 0) { /* Compare */ @@ -1090,10 +1268,12 @@ static enum emulation_result kvm_trap_vz_handle_gsfc(u32 cause, u32 *opc, /* DC bit enabling/disabling timer? */ if (change & CAUSEF_DC) { - if (val & CAUSEF_DC) + if (val & CAUSEF_DC) { + kvm_vz_lose_htimer(vcpu); kvm_mips_count_disable_cause(vcpu); - else + } else { kvm_mips_count_enable_cause(vcpu); + } } /* Only certain bits are RW to the guest */ @@ -2863,6 +3043,7 @@ static int kvm_vz_vcpu_run(struct kvm_run *run, struct kvm_vcpu *vcpu) int cpu = smp_processor_id(); int r; + kvm_vz_acquire_htimer(vcpu); /* Check if we have any exceptions/interrupts pending */ kvm_mips_deliver_interrupts(vcpu, read_gc0_cause()); |
