[PATCH 06/13] selftests/nolibc: allow specify a bios for qemu

[Zhangjin Wu]

Hi, Conor.

> 
> On Fri, May 26, 2023 at 06:25:18PM +0800, Zhangjin Wu wrote:
> 
> > > On 2023-05-25 01:52:29+0800, Zhangjin Wu wrote:
> > > > riscv qemu has a builtin bios (opensbi), but it may not match the latest
> > > > kernel and some old versions may hang during boot, let's allow user pass
> > > > a newer version to qemu via the -bios option.
> > >
> > > Nitpick:
> > >
> > > This seems very specific and hopefully only necessary temporarily.
> > >
> >
> > RISC-V is such a new ISA and the Spec (especially the SBI) changes very
> > frequently ;-)
> 
> Huh. Could you please expand on which versions of QEMU will hang while
> booting an upstream or stable kernel? Which kernels would be good to
> know too.
> 

As the cover letter listed (in the Environment section), the softwares we
used are:

    // higher qemu version is better, latest version is v8.0.0+
    $ qemu-system-riscv64  --version
    QEMU emulator version 4.2.1 (Debian 1:4.2-3ubuntu6.18)
    Copyright (c) 2003-2019 Fabrice Bellard and the QEMU Project developers

    // opensbi version, higher is better, must match kernel version and qemu version
    // rv64: used version is 1.2, latest is 1.2
    $ head -2 /labs/linux-lab/src/linux-stable/tools/testing/selftests/nolibc/run.out | tail -1
    OpenSBI v1.2-116-g7919530
    // rv32: used version is v0.9, latest is 1.2
    $ head -2 /labs/linux-lab/src/linux-stable/tools/testing/selftests/nolibc/run.out | tail -1
    OpenSBI v0.9-152-g754d511

The kernel version is the one this patchset based on (Willy's nolibc
repo), it is v6.4-rc1.

qemu v4.2.1 is the one systematically installed (/usr/bin) from the
qemu-system-misc package and used to test this patchset in my Ubuntu
20.04 based test docker image.

Just installed a v7.0.0 qemu from ppa:canonical-server/server-backports,
there is no default opensbi, and re-checked, there is one prebuilt
opensbi for rv64, but still no prebuilt opensbi for rv32.

    $ sudo add-apt-repository ppa:canonical-server/server-backports
    $ sudo apt install qemu-system-misc

    $ sudo apt install opensbi
    $ dpkg -S opensbi | grep -E "fw_*bin|elf"
    qemu-system-data: /usr/share/qemu/opensbi-riscv64-generic-fw_dynamic.elf
    opensbi: /usr/lib/riscv64-linux-gnu/opensbi/generic/fw_dynamic.elf
    opensbi: /usr/lib/riscv64-linux-gnu/opensbi/generic/fw_jump.elf

    $ qemu-system-riscv32 -display none -no-reboot -kernel build/riscv32/virt/linux/v6.4-rc1/arch/riscv/boot/Image -serial stdio -M virt -append "console=ttyS0 panic=-1"
    qemu-system-riscv32: Unable to load the RISC-V firmware "opensbi-riscv32-generic-fw_dynamic.bin"

I used the one built myself, If not want to build such opensbi manually,
we can download one (1.2 currently) from qemu source code:

    https://gitlab.com/qemu-project/qemu/-/blob/master/pc-bios/opensbi-riscv32-generic-fw_dynamic.bin

Then, we can use it like this:

    $ qemu-system-riscv32 -display none -no-reboot -kernel build/riscv32/virt/linux/v6.4-rc1/arch/riscv/boot/Image -serial stdio -M virt -append "console=ttyS0 panic=-1" -bios /path/to/opensbi-riscv32-generic-fw_dynamic.bin

Will append this extra info in the commit message of the coming new
revision of this patch, thanks a lot.

The hang issue I mentioned may be using one of my older prebuilt version of
opensbi, I can not find which one it exactly is, so, please ignore that info,
will update that description too.

Btw, something not about this patch: qemu v8.0.0 seems not boot non-mmu
v6.3, both sides have issues, not dig into it carefully, so, not report
it yet.

Thanks,
Zhangjin

> Thanks,
> Conor.