Re: qemu direct kernel boot on LoongArch

["Thomas Weißschuh" <thomas@t-8ch.de>]

On 2024-09-05 16:53:55+0000, Jason A. Donenfeld wrote:
> On Thu, Sep 05, 2024 at 07:25:05AM +0200, Thomas Weißschuh wrote:
> > On 2024-09-05 06:04:12+0000, Jason A. Donenfeld wrote:
> > > On Thu, Sep 5, 2024 at 5:45 AM maobibo <maobibo@loongson.cn> wrote:
> > > >
> > > > Jason,
> > > >
> > > > With the latest qemu 9.1 version, elf format booting is supported.
> > > 
> > > Thanks, I just figured this out too, about 4 minutes ago. Excellent.
> > > And the 1G minimum ram limit is gone too.
> > > 
> > > Now working on how to trigger resets.
> > 
> > With "reset" do you mean normal (non-panic) system shutdown/poweroff?
> > Since QEMU 9.1 and a recent kernel you can use the pvpanic device for
> > that in a cross-architecture way.
> 
> What I mean is that I need for userspace calling `reboot(RB_AUTOBOOT);`
> to actually result in QEMU being told to reboot the system. Sounds like
> that's not possible (yet?) in 9.1?

With reboot(RB_POWER_OFF) this is indeed the exact usecase for pvpanic
shutdown support. Reboot is not supported, but maybe -action
shutdown=reboot works and is enough. It would also be trivial to extend
pvpanic for reboot support.

Use -device pvpanic-pci for QEMU and CONFIG_PVPANIC_PCI=y for Linux.
(That should work for most architectures)