On 26 January 2018 at 17:05, Wei Xu <xuw...@hisilicon.com> wrote: > On 2018/1/26 16:36, Peter Maydell wrote: >> If the user presses keys before interrupts are enabled, >> what ought to happen is: >> * we put the key in the FIFO, and update the int_level flags >> * when the FIFO is full, can_receive starts returning 0 and >> QEMU stops passing us new characters >> * when the guest driver for the pl011 initializes the >> device and enables interrupts then either: >> (a) it does something that clears the FIFO, which will >> mean can_receive starts allowing new chars again, or >> (b) it leaves the FIFO as it is, and we should thus >> immediately raise an interrupt for the characters still >> in the FIFO; when the guest handles this interrupt and >> gets the characters, can_receive will permit new ones >> > > Yes, now it is handled like b. > >> What is happening in your situation that means this is not >> working as expected ? > > But in the kernel side, the pll011 is triggered as a level interruption. > During the booting, if any key is pressed ,the call stack is as below: > QEMU side: > pl011_update > -->qemu_set_irq(level as 0) > ---->kvm_arm_gic_set_irq > > Kernel side: > kvm_vm_ioctl_irq_line > -->kvm_vgic_inject_irq > ---->vgic_validate_injection (if level did not change, return) > ---->vgic_queue_irq_unlock > > Without above changes, in the vgic_validate_injection, because the > interruption level is always 0, this irq will not be queued into vgic. > And the guest will not read the pl011 fifo.
The pl011 code should call qemu_set_irq(..., 1) when the guest enables interrupts on the device by writing to the int_enabled (UARTIMSC) register. That will be a 0-to-1 level change and the KVM VGIC should report the interrupt to the guest. thanks -- PMM
