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Subject: Re: [Qemu-devel] [PATCH v5 2/2] hw/arm: add Arm SBSA reference
 machine, devices part
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To: Peter Maydell <peter.maydell@linaro.org>
Cc: Hongbo Zhang <hongbo.zhang@linaro.org>, Radoslaw Biernacki <radoslaw.biernacki@linaro.org>, Ard Biesheuvel <ard.biesheuvel@linaro.org>, QEMU Developers <qemu-devel@nongnu.org>, Leif Lindholm <leif.lindholm@linaro.org>, qemu-arm <qemu-arm@nongnu.org>, Alex =?UTF-8?Q?Benn=C3=A9e?= <alex.bennee@linaro.org>

On Tue, 29 Jan 2019 15:26:29 +0000
Peter Maydell <peter.maydell@linaro.org> wrote:

> On Mon, 28 Jan 2019 at 09:46, Hongbo Zhang <hongbo.zhang@linaro.org> wrote:
> >
> > On Tue, 22 Jan 2019 at 19:49, Peter Maydell <peter.maydell@linaro.org> wrote:
> > >
> > > On Fri, 7 Dec 2018 at 09:08, Hongbo Zhang <hongbo.zhang@linaro.org> wrote:
> > > > +static void sbsa_ref_machine_done(Notifier *notifier, void *data)
> > > > +{
> > > > +    VirtMachineState *vms = container_of(notifier, VirtMachineState,
> > > > +                                         machine_done);
> > > > +    ARMCPU *cpu = ARM_CPU(first_cpu);
> > > > +    struct arm_boot_info *info = &vms->bootinfo;
> > > > +    AddressSpace *as = arm_boot_address_space(cpu, info);
> > > > +
> > > > +    if (arm_load_dtb(info->dtb_start, info, info->dtb_limit, as) < 0) {
> > > > +        exit(1);
> > > > +    }
> > > > +}
> > >
> > > I still don't understand why we need this -- it doesn't seem
> > > to be doing anything different from the default behaviour that
> > > boot.c implements if skip_dtb_autoload is false.
> > >
> >
> > According to the process of arm_load_kernel() in boot.c, If only
> > kernel loaded via -kernel but without any firmware, it works fine.
> > While in this case, we have have firmware loaded but no kernel (eg
> > firmware loads kernel from storage, firmware never come back to qemu
> > again), so the arm_load_kernel() returns in the middle before calling
> > arm_load_dtb(),  because arm_load_dtb() is the final step in
> > arm_load_kernel(), so there is no chance for the arm_load_dtb() to be
> > called, then we get error message and qemu quits.
> 
> Oh, I see now. I think this is a bug in boot.c and we should
> fix it by making the "this is a firmware boot" code path also
> do the arm_load_dtb() call. I'll send a patch.
pls, CC me on it as well.

I'm interested in it from hotplug + reboot perspective,
where we have a changed/bigger DTB on reboot as it contains new devices (cpus|memory)

loading rom like now doesn't work nice in case of reboot.

> 
> thanks
> -- PMM
>