Re: [Qemu-devel] [PATCH v3] hw/core/null-machine: Add the possibility to instantiate a CPU and RAM

[Alistair Francis <alistair.francis@xilinx.com>]

On Wed, Jan 18, 2017 at 10:56 AM, Thomas Huth <thuth@redhat.com> wrote:
> On 18.01.2017 18:57, Alistair Francis wrote:
>> On Wed, Jan 18, 2017 at 4:44 AM, Thomas Huth <thuth@redhat.com> wrote:
>>> Sometimes it is useful to have just a machine with CPU and RAM, without
>>> any further hardware in it, e.g. if you just want to do some instruction
>>> debugging for TCG with a remote GDB attached to QEMU, or run some embedded
>>> code with the "-semihosting" QEMU parameter. qemu-system-m68k already
>>> features a "dummy" machine, and xtensa a "sim" machine for exactly this
>>> purpose.
>>> All target architectures have nowadays also a "none" machine, which would
>>> be a perfect match for this, too - but it currently does not allow to add
>>> CPU and RAM yet. Thus let's add these possibilities in a generic way to the
>>> "none" machine, too, so that we hopefully do not need additional "dummy"
>>> machines in the future anymore (and maybe can also get rid of the already
>>> existing "dummy"/"sim" machines one day).
>>> Note that the default behaviour of the "none" machine is not changed, i.e.
>>> no CPU and no RAM is instantiated by default. You have explicitely got to
>>> specify the CPU model with "-cpu" and the amount of RAM with "-m" to get
>>> these new features.
>>>
>>> Signed-off-by: Thomas Huth <thuth@redhat.com>
>>> ---
>>>  v3:
>>>  - Get rid of the cpu_init_def() wrapper again, make null-machine.o
>>>    target dependent instead and use cpu_init() directly.
>>>  - Omit the loader code for the "-kernel" option for now (users can
>>>    use "-device loader,..." instead). We can add code for the -kernel
>>>    parameter later (either an implementation or a warning), once we've
>>>    decided how it should behave for the "none" machine.
>>
>> I think there should at least be a warning to start with though. It
>> seems confusing that no errors are reported but the argument is
>> ignored.
>
> I'm still rather in favor of adding the hunk here that calls the generic
> loader for "-kernel" ... anyway, we can add either behavior with a later
> patch. So far the "none" machine never reported an error here, so this
> is not a regression if we do not have this right from the start.

Your right, it isn't a regression. I still think we should try to get
some sort of action in there before the next release.

Reviewed-by: Alistair Francis <alistair.francis@xilinx.com>

Thanks,

Alistair

>
>  Thomas
>
>