Re: [Xen-devel] [PATCH v3 18/19] hw/arm: Do not build to 'virt' machine on Xen

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Mon, 16 Mar 2020, Philippe Mathieu-Daudé wrote:
> Xen on ARM does not use QEMU machines [*]. Disable the 'virt'
> machine there to avoid odd errors such:
> 
>     CC      i386-softmmu/hw/cpu/a15mpcore.o
>   hw/cpu/a15mpcore.c:28:10: fatal error: kvm_arm.h: No such file or directory
> 
> [*] 
> https://wiki.xenproject.org/wiki/Xen_ARM_with_Virtualization_Extensions#Use_of_qemu-system-i386_on_ARM


I confirm that what's written on that wikipage is correct: Xen on ARM
doesn't use QEMU for emulation, only as a PV backends provider. As such,
and also because the code is a bit entangled with the x86 platform, even
on ARM we are building and running qemu-system-i386 to get the PV disk
and PV framebuffer. Of course, no x86 emulation is actually done.

Ideally we would have a non-arch-specific machine type for the PV
backends, but that doesn't exist today.

In short, I think this patch is fine, at least until somebody comes
around and tries to add emulation to Xen on ARM.



> Signed-off-by: Philippe Mathieu-Daudé <philmd@xxxxxxxxxx>
> ---
> Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
> Cc: Anthony Perard <anthony.perard@xxxxxxxxxx>
> Cc: Paul Durrant <paul@xxxxxxx>
> Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx
> ---
>  hw/arm/Kconfig | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/hw/arm/Kconfig b/hw/arm/Kconfig
> index 8e801cd15f..69a8e30125 100644
> --- a/hw/arm/Kconfig
> +++ b/hw/arm/Kconfig
> @@ -1,5 +1,6 @@
>  config ARM_VIRT
>      bool
> +    depends on !XEN
>      default y if KVM
>      imply PCI_DEVICES
>      imply TEST_DEVICES
> -- 
> 2.21.1
>

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