From: "Scott J. Goldman" <[email protected]> Commit b5f8f77271 ("accel/hvf: Implement WFI without using pselect()") changed hvf_wfi() from blocking the vCPU thread with pselect() to returning EXCP_HLT, intending QEMU's main event loop to handle the idle wait. However, cpu->halted was never set, so cpu_thread_is_idle() always returns false and the vCPU thread spins at 100% CPU per core while the guest is idle.
Fix this by: 1. Setting cpu->halted = 1 in hvf_wfi() so the vCPU thread sleeps on halt_cond in qemu_process_cpu_events(). 2. Arming a per-vCPU QEMU_CLOCK_VIRTUAL timer to fire when the guest's virtual timer (CNTV_CVAL_EL0) would expire. This is necessary because HVF only delivers HV_EXIT_REASON_VTIMER_ACTIVATED during hv_vcpu_run(), which is not called while the CPU is halted. The timer callback mirrors the VTIMER_ACTIVATED handler: it raises the vtimer IRQ through the GIC and marks vtimer_masked, causing the interrupt delivery chain to wake the vCPU via qemu_cpu_kick(). 3. Clearing cpu->halted in hvf_arch_vcpu_exec() when cpu_has_work() indicates a pending interrupt, and cancelling the WFI timer. 4. Re-arming the WFI timer from hvf_vm_state_change() on the resume transition for any halted vCPU, since the QEMUTimer is per-instance state and is not migrated. After cpu_synchronize_all_states() the migrated vtimer state is mirrored in env, so we can read CNTV_CTL and CNTV_CVAL from there. If the vtimer has already expired by the time the destination resumes, hvf_wfi_timer_cb() is invoked directly so the halted vCPU is woken up. All wfi_timer handling (allocation, arming, deletion, and the resume re-arm) is gated on !hvf_irqchip_in_kernel(): with the Apple in-kernel vGIC, HVF owns the vtimer and delivers wake-ups itself. Note for stable backports: this commit won't apply to 11.0 as it has changes to handle the hvf in-kernel irqchip support that landed after the 11.0 release. The v3 version of this commit: https://patchew.org/QEMU/[email protected]/ should be suitable for 11.0 backporting (it is essentially identical except that it doesn't make the changes conditional on !hvf_irqchip_in_kernel()). Cc: [email protected] Fixes: b5f8f77271 ("accel/hvf: Implement WFI without using pselect()") Signed-off-by: Scott J. Goldman <[email protected]> Reviewed-by: Mohamed Mediouni <[email protected]> [PMM: added note about stable backports to commit message] Signed-off-by: Peter Maydell <[email protected]> (cherry picked from commit a86024eb2df56f7664cef16ec8e9a50a1dc3dd2f) (Mjt: add hvf_irqchip_in_kernel() define) Signed-off-by: Michael Tokarev <[email protected]> diff --git a/include/system/hvf_int.h b/include/system/hvf_int.h index 2621164cb2..58fb865eba 100644 --- a/include/system/hvf_int.h +++ b/include/system/hvf_int.h @@ -48,6 +48,7 @@ struct AccelCPUState { hv_vcpu_exit_t *exit; bool vtimer_masked; bool guest_debug_enabled; + struct QEMUTimer *wfi_timer; #endif }; diff --git a/target/arm/hvf/hvf.c b/target/arm/hvf/hvf.c index 5fc8f6bbbd..5016783062 100644 --- a/target/arm/hvf/hvf.c +++ b/target/arm/hvf/hvf.c @@ -28,6 +28,7 @@ #include "hw/core/boards.h" #include "hw/core/irq.h" #include "qemu/main-loop.h" +#include "qemu/timer.h" #include "system/cpus.h" #include "arm-powerctl.h" #include "target/arm/cpu.h" @@ -40,6 +41,8 @@ #include "gdbstub/enums.h" +#define hvf_irqchip_in_kernel() 0 /* stub for qemu 11.0.x */ + #define MDSCR_EL1_SS_SHIFT 0 #define MDSCR_EL1_MDE_SHIFT 15 @@ -301,6 +304,8 @@ void hvf_arm_init_debug(void) #define TMR_CTL_IMASK (1 << 1) #define TMR_CTL_ISTATUS (1 << 2) +static void hvf_wfi_timer_cb(void *opaque); + static uint32_t chosen_ipa_bit_size; typedef struct HVFVTimer { @@ -1214,6 +1219,11 @@ void hvf_arch_vcpu_destroy(CPUState *cpu) { hv_return_t ret; + if (!hvf_irqchip_in_kernel()) { + timer_free(cpu->accel->wfi_timer); + cpu->accel->wfi_timer = NULL; + } + ret = hv_vcpu_destroy(cpu->accel->fd); assert_hvf_ok(ret); } @@ -1352,6 +1362,11 @@ int hvf_arch_init_vcpu(CPUState *cpu) arm_cpu->isar.idregs[ID_AA64MMFR0_EL1_IDX]); assert_hvf_ok(ret); + if (!hvf_irqchip_in_kernel()) { + cpu->accel->wfi_timer = timer_new_ns(QEMU_CLOCK_VIRTUAL, + hvf_wfi_timer_cb, cpu); + } + aarch64_add_sme_properties(OBJECT(cpu)); return 0; } @@ -2027,6 +2042,62 @@ static uint64_t hvf_vtimer_val_raw(void) return mach_absolute_time() - hvf_state->vtimer_offset; } +static void hvf_wfi_timer_cb(void *opaque) +{ + CPUState *cpu = opaque; + ARMCPU *arm_cpu = ARM_CPU(cpu); + + /* + * vtimer expired while the CPU was halted for WFI. + * Mirror HV_EXIT_REASON_VTIMER_ACTIVATED: raise the vtimer + * interrupt and mark as masked so hvf_sync_vtimer() will + * check and unmask when the guest handles it. + * + * The interrupt delivery chain (GIC -> cpu_interrupt -> + * qemu_cpu_kick) wakes the vCPU thread from halt_cond. + */ + qemu_set_irq(arm_cpu->gt_timer_outputs[GTIMER_VIRT], 1); + cpu->accel->vtimer_masked = true; +} + +/* + * Arm a host-side QEMU_CLOCK_VIRTUAL timer to fire when the guest's + * vtimer (CNTV_CVAL_EL0) is scheduled to expire. HVF only delivers + * HV_EXIT_REASON_VTIMER_ACTIVATED during hv_vcpu_run(), which we won't + * call while the vCPU is halted, so we need this to wake the vCPU. + * + * QEMU_CLOCK_VIRTUAL pauses while the VM is stopped, which keeps the + * timer in lockstep with the guest's view of vtime across pause/resume. + * + * Caller must supply the current CNTV_CTL_EL0 and CNTV_CVAL_EL0 values, + * since the appropriate source (HVF vs. env) depends on context. + * + * Returns 0 if the timer was armed (or if the vtimer is disabled/masked + * and the vCPU should still halt waiting on another event), or -1 if + * the vtimer has already expired. + */ +static int hvf_arm_wfi_timer(CPUState *cpu, uint64_t ctl, uint64_t cval) +{ + ARMCPU *arm_cpu = ARM_CPU(cpu); + uint64_t now; + int64_t delta_ns; + + if (!(ctl & TMR_CTL_ENABLE) || (ctl & TMR_CTL_IMASK)) { + return 0; + } + + now = hvf_vtimer_val_raw(); + if (cval <= now) { + return -1; + } + + delta_ns = muldiv64(cval - now, NANOSECONDS_PER_SECOND, + arm_cpu->gt_cntfrq_hz); + timer_mod(cpu->accel->wfi_timer, + qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) + delta_ns); + return 0; +} + static int hvf_wfi(CPUState *cpu) { if (cpu_has_work(cpu)) { @@ -2037,6 +2108,29 @@ static int hvf_wfi(CPUState *cpu) return 0; } + if (!hvf_irqchip_in_kernel()) { + uint64_t ctl, cval; + hv_return_t r; + + /* + * Read the vtimer state directly from HVF. We're on the vCPU + * thread, just exited from hv_vcpu_run(), so HVF holds the + * authoritative values and env may be stale. + */ + r = hv_vcpu_get_sys_reg(cpu->accel->fd, HV_SYS_REG_CNTV_CTL_EL0, + &ctl); + assert_hvf_ok(r); + r = hv_vcpu_get_sys_reg(cpu->accel->fd, HV_SYS_REG_CNTV_CVAL_EL0, + &cval); + assert_hvf_ok(r); + + if (hvf_arm_wfi_timer(cpu, ctl, cval) < 0) { + /* vtimer already expired, don't halt */ + return 0; + } + } + + cpu->halted = 1; return EXCP_HLT; } @@ -2332,7 +2426,13 @@ int hvf_arch_vcpu_exec(CPUState *cpu) hv_return_t r; if (cpu->halted) { - return EXCP_HLT; + if (!cpu_has_work(cpu)) { + return EXCP_HLT; + } + cpu->halted = 0; + if (!hvf_irqchip_in_kernel()) { + timer_del(cpu->accel->wfi_timer); + } } flush_cpu_state(cpu); @@ -2381,6 +2481,46 @@ static void hvf_vm_state_change(void *opaque, bool running, RunState state) /* Update vtimer offset on all CPUs */ hvf_state->vtimer_offset = mach_absolute_time() - s->vtimer_val; cpu_synchronize_all_states(); + + /* + * After migration restore (or any resume), the wfi_timer is not + * scheduled on this QEMU instance, so re-arm it for any halted + * vCPU with a pending vtimer. For a non-migration resume the + * QEMU_CLOCK_VIRTUAL timer was already scheduled; recomputing the + * deadline produces the same value and is a harmless no-op. + * + * cpu_synchronize_all_states() above ensures env mirrors the + * authoritative vtimer state (whether that came from HVF or from + * the migration stream), so we can safely read it here from the + * iothread. + * + * Only applies when we own the wfi_timer; with an in-kernel vGIC + * the timer is never allocated and HVF handles vtimer wake-ups. + */ + if (!hvf_irqchip_in_kernel()) { + CPUState *cpu; + + CPU_FOREACH(cpu) { + ARMCPU *arm_cpu; + uint64_t ctl, cval; + + if (!cpu->accel || !cpu->halted) { + continue; + } + + arm_cpu = ARM_CPU(cpu); + ctl = arm_cpu->env.cp15.c14_timer[GTIMER_VIRT].ctl; + cval = arm_cpu->env.cp15.c14_timer[GTIMER_VIRT].cval; + + if (hvf_arm_wfi_timer(cpu, ctl, cval) < 0) { + /* + * vtimer already expired while we were paused; raise + * the IRQ now so the halted vCPU wakes up. + */ + hvf_wfi_timer_cb(cpu); + } + } + } } else { /* Remember vtimer value on every pause */ s->vtimer_val = hvf_vtimer_val_raw(); -- 2.47.3
