aarch64 u-boot reset loop with qemu USB and KVM

[Ilias Apalodimas]

Hi Mikko

On Mon, 2 Jun 2025 at 14:24, Mikko Rapeli <mikko.rapeli at linaro.org> wrote:
>
> Hi,
>
> On Mon, Jun 02, 2025 at 01:28:38PM +0300, Mikko Rapeli wrote:
> > As was discussed over yocto/OE-Core mailing list
> > https://lists.openembedded.org/g/openembedded-core/topic/113306017#msg217258
> > qemu machine with USB and KVM enabled goes into reset loop with
> > u-boot. I've tested u-boot 2025.04 and latest master branch 2025.07-rc3
> > ( b22a276f039f818d5564bec6637071cfc8a7e432 ) with qemu_arm64_defconfig
> > from tree and CONFIG_BLOBLIST disabled since that to has issues with KVM
> > ( https://lists.denx.de/pipermail/u-boot/2025-May/590101.html )-
> >
> > To reproduce:
> >
> >  * qemu 10 or 8.2.2, version does not seem to matter
> >
> >  * aarch64 native machine with KVM support
> >
> >  * qemu-system-aarch64 command line:
> >
> > $ qemu-system-aarch64 -machine virt -cpu host -machine gic-version=3 -smp 1 -enable-kvm \
> >   -m 256 -serial mon:stdio -serial null -nographic -vga none \
> >   -bios u-boot.bin \
> >   -device qemu-xhci -device usb-tablet -device usb-kbd
> >
> > U-Boot 2025.07-rc3 (May 30 2025 - 19:44:05 +0000)
> >
> > DRAM:  256 MiB
> > using memory 0x4e662000-0x4f6a2000 for malloc()
> > Core:  51 devices, 14 uclasses, devicetree: board
> > Flash: 64 MiB
> > Loading Environment from Flash... *** Warning - bad CRC, using default environment
> >
> > In:    serial,usbkbd
> > Out:   serial,vidconsole
> > Err:   serial,vidconsole
> > Register 8001040 NbrPorts 8
> > Starting the controller
> > "Synchronous Abort" handler, esr 0x96000010, far 0x10100040
> > elr: 000000000005a360 lr : 000000000005a344 (reloc)
> > elr: 000000004f6fc360 lr : 000000004f6fc344
> > x0 : 0000000010100040 x1 : 0000000000000001
> > x2 : 0000000000000000 x3 : 0000000000003e80
> > x4 : 0000000000000038 x5 : 000000004e66fed2
> > x6 : 0000000000000000 x7 : 0000000000000000
> > x8 : 0000000000000000 x9 : 000000000001869f
> > x10: 000000000000000d x11: 0000000000000006
> > x12: 000000004e561a68 x13: 000000004e561dd0
> > x14: 0000000000000002 x15: 0000000000000000
> > x16: 000000004f6ee774 x17: 0000000000000000
> > x18: 000000004e661dd0 x19: 000000004e670480
> > x20: 0000000000000000 x21: 0000000010100040
> > x22: 0000000010100000 x23: 0000000000000000
> > x24: 0000000000000000 x25: 0000000000000000
> > x26: 0000000000000000 x27: 0000000000000000
> > x28: 0000000000000000 x29: 000000004e670360
> >
> > Code: d5033fbf aa1503e0 5287d003 52800002 (b8004401)
> > Resetting CPU ...
> >
> > resetting ...
> >
> > With KVM disabled, or the qemu USB devices disabled, boot with u-boot prompt and
> > to full target system works.
>
> I've bisected this now and first breaking commit is:

Thanks for looking into this.
The commit just enables the support for a usb keyboard, so I think the
root cause was always there.

Cheers
/Ilias
>
> 05e2fa79310ab30dd3e3fe522333aef3cfb1c421 is the first bad commit
> commit 05e2fa79310ab30dd3e3fe522333aef3cfb1c421
> Author: Alper Nebi Yasak <alpernebiyasak at gmail.com>
> Date:   Mon Aug 14 20:39:43 2023 +0300
>
>     arm: qemu: Enable usb keyboard as an input device
>
>     Commit 02be57caf730 ("riscv: qemu: Enable usb keyboard as an input
>     device") adds PCI xHCI support to QEMU RISC-V virtual machines and
>     enables using a USB keyboard as one of the input devices. Similarly,
>     enable those for ARM virtual machines as well.
>
>     Signed-off-by: Alper Nebi Yasak <alpernebiyasak at gmail.com>
>     Reviewed-by: Simon Glass <sjg at chromium.org>
>     Reviewed-by: Bin Meng <bmeng at tinylab.org>
>
>  arch/arm/Kconfig                      | 5 +++++
>  board/emulation/qemu-arm/qemu-arm.c   | 5 +++++
>  board/emulation/qemu-arm/qemu-arm.env | 2 +-
>  configs/qemu_arm64_defconfig          | 2 --
>  configs/qemu_arm_defconfig            | 2 --
>  doc/board/emulation/qemu-arm.rst      | 4 ++++
>  6 files changed, 15 insertions(+), 5 deletions(-)
>
> So looks like with KVM, CONFIG_USB=y triggers the reset loop.
>
> Cheers,
>
> -Mikko