Re: [wrynose][PATCH] qemuriscv.inc: use fw_dynamic.elf as BIOS when KERNEL_DEBUG is enabled

["Trevor Gamblin" <tgamblin@baylibre.com>]

On Wed Sep 16, 2026 at 8:15 AM EDT, Harish.Sadineni wrote:
> From: Harish Sadineni <Harish.Sadineni@windriver.com>
>
> QEMU RISC-V hangs (qemu hang-up) when using fw_jump.elf as the
> default BIOS while kernel debugging is enabled. This has been
> observed with the 6.18 kernel (exact version where it was
> introduced is not known).
>
> As a workaround, switch to fw_dynamic.elf when KERNEL_DEBUG is
> enabled, which avoids the hang and works correctly with debug
> builds. The default behaviour is unchanged and continues to use
> fw_jump.elf when KERNEL_DEBUG is not set.

It'd be good to understand exactly why this doesn't work and what changed
upstream. I'm looking into it in a local checkout, but I probably won't have an
answer for a day or two.

Trevor
>
> [YOCTO #16409]
>
> Signed-off-by: Harish Sadineni <Harish.Sadineni@windriver.com>
> ---
>  meta/conf/machine/include/riscv/qemuriscv.inc | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/meta/conf/machine/include/riscv/qemuriscv.inc b/meta/conf/machine/include/riscv/qemuriscv.inc
> index bac376ce5a..6e7d4a8adf 100644
> --- a/meta/conf/machine/include/riscv/qemuriscv.inc
> +++ b/meta/conf/machine/include/riscv/qemuriscv.inc
> @@ -29,7 +29,10 @@ QB_SMP ?= "-smp 4"
>  QB_KERNEL_CMDLINE_APPEND = "earlycon=sbi"
>  QB_CPU:riscv64 ?= "-cpu rva23s64,pmp=true"
>  QB_MACHINE = "-machine virt"
> -QB_DEFAULT_BIOS = "fw_jump.elf"
> +# Workaround: fw_jump.elf causes QEMU RISC-V to hang when KERNEL_DEBUG
> +# is enabled, use fw_dynamic.elf in that case instead.
> +# See https://bugzilla.yoctoproject.org/show_bug.cgi?id=16409 for more details.
> +QB_DEFAULT_BIOS = "${@bb.utils.contains('KERNEL_DEBUG', 'True', 'fw_dynamic.elf', 'fw_jump.elf', d)}"
>  QB_TAP_OPT = "-netdev tap,id=net0,ifname=@TAP@,script=no,downscript=no"
>  QB_NETWORK_DEVICE = "-device virtio-net-device,netdev=net0,mac=@MAC@"
>  QB_ROOTFS_OPT = "-drive id=disk0,file=@ROOTFS@,if=none,format=raw -device virtio-blk-device,drive=disk0"