Re: [PATCH v3 17/19] hw/arm: Automatically select the 'virt' machine on KVM

[Philippe Mathieu-Daudé]

On 9/29/20 10:11 PM, Peter Maydell wrote:
> On Tue, 29 Sep 2020 at 21:06, Peter Maydell <peter.maydell@linaro.org> wrote:
>>
>> On Mon, 16 Mar 2020 at 16:08, Philippe Mathieu-Daudé <philmd@redhat.com> 
>> wrote:
>>>
>>> When building a KVM-only QEMU, the 'virt' machine is a good
>>> default :)
>>>
>>> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
>>> ---
>>>  hw/arm/Kconfig | 1 +
>>>  1 file changed, 1 insertion(+)
>>>
>>> diff --git a/hw/arm/Kconfig b/hw/arm/Kconfig
>>> index d0903d8544..8e801cd15f 100644
>>> --- a/hw/arm/Kconfig
>>> +++ b/hw/arm/Kconfig
>>> @@ -1,5 +1,6 @@
>>>  config ARM_VIRT
>>>      bool
>>> +    default y if KVM
>>>      imply PCI_DEVICES
>>>      imply TEST_DEVICES
>>>      imply VFIO_AMD_XGBE
>>
>> What does this actually do ? Why should the choice of
>> accelerator affect what boards we pull in by default?
> 
> Put another way, our current default is "build everything",
> so "default y if ..." on a board is a no-op...

Yes, the problem if I don't restrict to KVM, when
using the Xen accelerator odd things occur
(using configure --enable-xen --disable-tcg --disable-kvm):

Compiling C object libqemu-i386-softmmu.fa.p/hw_cpu_a15mpcore.c.o
hw/cpu/a15mpcore.c:28:10: fatal error: kvm_arm.h: No such file or directory

See
https://wiki.xenproject.org/wiki/Xen_ARM_with_Virtualization_Extensions#Use_of_qemu-system-i386_on_ARM

We can't have the 'virt' machine automatically selected if
Xen is the only accelerator...

I'm looking for a simple way to avoid modifying the Xen code.

> 
> -- PMM
>