RISC-V u-boot unable to boot QEMU using '-cpu max'

[Leo Liang]

On Mon, Apr 22, 2024 at 04:43:59PM -0300, Daniel Henrique Barboza wrote:
> [EXTERNAL MAIL]
> 
> Hi,
> 
> In QEMU we have a 'max' type CPU that implements (almost) all extensions that QEMU
> is able to emulate. Recently, in QEMU commit 249e0905d05, we bumped the extensions
> for this CPU.
> 
> And after this commit this CPU is now unable to boot a guest using upstream
> u-boot. Here's the error being thrown:
> 
> qemu-system-riscv64 \
>         -machine virt -nographic -m 8G -smp 8 \
>         -cpu max -kernel uboot.elf (...)
> (...)
> 
> initcall sequence 000000008027c3e8 failed at call 000000008021259e (err=-28)
> ### ERROR ### Please RESET the board ###
> 
> 
> I can get the guest to boot if I disable the following extensions from the 'max' CPU:
> 
>  -cpu max,zfbfmin=false,zvfbfmin=false,zvfbfwma=false
> 
> Due to QEMU extension dependencies I'm not able to disable these individually. What I can
> say is that u-boot isn't playing ball to at least one of them.
> 
> Is this an u-boot bug? Up to this point I was assuming that u-boot would silently ignore
> hart extensions that it doesn't support.

Hi Daniel,

Which u-boot version are you using?

I think this issue is fixed by the following patch set sent by Conor.

	f39b1b77d8 riscv: support extension probing using riscv, isa-extensions
	b90edde701 riscv: don't read riscv, isa in the riscv cpu's get_desc()

I've tested and can reproduce the issue you mentioned if these two patches are reverted.

Could you try with the lastest u-boot master branch again?


For reference, my testing commands are as follows:
1. cd ${u-boot} && make qemu-riscv64_defconfig && make -j`nproc`
2. ./${qemu}/build/qemu-system-riscv64 -nographic -machine virt -cpu max -bios u-boot.bin -m 8G -smp 8

- u-boot branch (commit): master (38ea74d6d5c0 "Prepare v2024.07-rc1")
- qemu branch (commit): master (62dbe54c24db "Update version for v9.0.0-rc4 release")


Best regards,
Leo

> 
> 
> Thanks,
> 
> 
> Daniel