Hi Andrew, On 2018/1/29 10:29, Andrew Jones wrote: > On Fri, Jan 26, 2018 at 06:01:33PM +0000, Peter Maydell wrote: >> On 26 January 2018 at 17:33, Wei Xu <xuw...@hisilicon.com> wrote: >>> On 2018/1/26 17:15, Peter Maydell wrote: >>>> 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. >>>> >>> >>> Yes. >>> And in the pl011_update, the irq level is set by s->int_level & >>> s->int_enabled. >>> When writing to the int_enabled, not sure why the int_level is set to >>> 0x20(PL011_INT_TX) but int_enabled is 0x50. >>> >>> It still call qemu_set_irq(..., 0). >>> >>> I added "s->int_level |= PL011_INT_RX" before calling pl011_update >>> when writing to the int_enabled and tested it also works. >> >> No, that's not right either. int_level should already have the >> RX bit set, because pl011_put_fifo() sets that bit when it gets a >> character from QEMU and puts it into the FIFO. >> >> Does something else clear the int_level between the character >> going into the FIFO from QEMU and the guest enabling >> interrupts? > > As part of the boot process Linux restarts the UART a few times. When > Linux drives the PL011 with the SBSA driver then the FIFO doesn't get > reset prior to being used again, as the SBSA doesn't specify a way to > do that. I'm not sure if this issue is due to the SBSA attempting to > be overly simple, or something the Linux driver can deal with. See > this thread for a discussion I started once. > > https://www.spinics.net/lists/linux-serial/msg23163.html
I am not sure it is the same problem or not. I will check that. Thanks! > > Wei, > > I assume you're using UEFI/ACPI when booting, as I don't recall this > problem occurring with the Linux PL011 driver which would be used > when booting with DT. > I am using an ARM64 board, the guest is booted *without* UEFI but the host is booted with UEFI/ACPI. The command I am using is as below: "qemu-system-aarch64 -enable-kvm -m 1024 -cpu host -M virt \ -nographic --kernel Image --initrd roofs.cpio.gz" Thanks! Best Regards, Wei > Thanks, > drew > > . >