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Date: Thu, 5 Sep 2024 17:16:12 +0200
From: Thomas =?utf-8?Q?Wei=C3=9Fschuh?= <thomas@t-8ch.de>
To: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: maobibo <maobibo@loongson.cn>, loongarch@lists.linux.dev, 
	qemu-devel@nongnu.org, xry111@xry111.site
Subject: Re: qemu direct kernel boot on LoongArch
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On 2024-09-05 17:07:22+0000, Jason A. Donenfeld wrote:
> On Thu, Sep 5, 2024 at 5:05 PM Thomas Weißschuh <thomas@t-8ch.de> wrote:
> >
> > 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
> 
> I'm actually using reboot(RB_AUTOBOOT) wth QEMU's -no-reboot, because
> that tends to be far more compatible with a greater number of
> platforms, for example, x86 without acpi. Shucks.

You can check that both QEMU and the kernel support pvpanic shutdown
through sysfs and if so use reboot(RB_POWER_OFF); and
reboot(RB_AUTOBOOT) otherwise.