On Tue May 12, 2026 at 1:54 PM EDT, Mohamed Mediouni wrote: > > >> On 27. Apr 2026, at 21:55, Scott J. Goldman <[email protected]> wrote: >> >> 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. >> >> Fixes: b5f8f77271 ("accel/hvf: Implement WFI without using pselect()") >> Signed-off-by: Scott J. Goldman <[email protected]> > > Hi, > > A bit of a side note for reproducing this: > > To reproduce this on current master, as far as I can tell you need either > -M kernel-irqchip=off or -M virt-11.0 or earlier. -M virt(-11.1) on master > uses > the HVF vGIC path.
Just wanted to confirm that I re-tested and it seems like you are correct. This must have changed semi recently? I was just running with `-M virt` before. Either way, it's good that the defaults seem to work better now. Either way, I guess the fix still needs to go in for the non vGIC path?
