Re: [Qemu-devel] [PATCH] hw/core/null-machine: Add the possibility to instantiate a CPU, RAM and kernel

[Eduardo Habkost]

On Tue, Jan 17, 2017 at 09:29:19AM +0000, Peter Maydell wrote:
> On 16 January 2017 at 19:44, Eduardo Habkost <address@hidden> wrote:
> > On Mon, Jan 16, 2017 at 07:27:21PM +0000, Peter Maydell wrote:
> >> On 16 January 2017 at 19:25, Eduardo Habkost <address@hidden> wrote:
> >> > On Mon, Jan 16, 2017 at 10:53:07AM -0800, Alistair Francis wrote:
> >> >> On Sun, Jan 15, 2017 at 11:59 PM, Thomas Huth <address@hidden> wrote:
> >> >> > But I think the users also expect the "-kernel" parameter to be 
> >> >> > working,
> >> >> > so I think we should add the loader code in null-machine.c anyway.
> >> >>
> >> >> I agree that uses probably expect the '-kernel' option to work as well.
> >> >
> >> > So, is it possible to write a generic load_kernel() function that
> >> > simply reuses the generic-loader code?
> >>
> >> No, because users expect -kernel to actually load a Linux kernel
> >> (meaning with the calling conventions etc the kernel requires),
> >> whereas generic-loader is just "load a binary blob and start there".
> >
> > I don't mean a generic function that works for all machines and
> > architectures, but a generic function that is good enough for
> > "-machine none". Isn't "load a binary blob and start there"
> > exactly what machine_none_load_kernel() in this patch does?
> 
> If you just want "load a blob and start it" then we already
> have -device loader. Making -kernel have yet another set of
> semantics that this time depends on the machine being selected
> seems like a bad idea. If -kernel doesn't do what it does
> for the other machines of the same architecture then we should
> just not accept it.

Good point. In this case, implementing -kernel on "-machine none"
will require calling an arch-specific hook from the beginning.
I'm not sure if it's worth the effort, but I won't object if
somebody really wants to implement that.

While this is not implemented, I suggest we make "-machine none"
reject -kernel instead of silently ignoring it.

-- 
Eduardo