Re: [Qemu-devel] [PATCH 01/22] configure: factor out list of supported Xen/KVM/HAX targets

[Paolo Bonzini]

On 04/07/2017 10:28, Daniel P. Berrange wrote:
>> +supported_kvm_target() {
>> +    test "$kvm" = "yes" || return 1
>> +    glob "$1" "*-softmmu" || return 1
>> +    case "${1%-softmmu}:$cpu" in
>> +        arm:arm | aarch64:aarch64 | \
>> +        i386:i386 | i386:x86_64 | i386:x32 | \
>> +        x86_64:i386 | x86_64:x86_64 | x86_64:x32 | \
> 
> IIUC, 'x86_64:i386' is claiming that you can run x86_64
> KVM guests on an i386 host. I thought that was impossible,
> only 32-on-64 being allowed not 64-on-32.

You can use qemu-system-x86_64 to run i386 KVM guests, by disabling long
mode with -cpu.  It's not a common scenario though.

>> +        mips:mips | mipsel:mips | \
>> +        ppc:ppc | ppcemb:ppc | ppc64:ppc | \
>> +        ppc:ppc64 | ppcemb:ppc64 | ppc64:ppc64 | \
> 
> Same question here with ppc64:ppc suggesting you can
> run 64-bit guest with KVM on a 32-bit host ?

I'm not sure about this one, but right now it is allowed so this patch
is not changing anything.

>> +        s390x:s390x)
>> +            return 0
>> +        ;;
>> +    esac
>> +    return 1
>> +}
>> +
>> +supported_xen_target() {
>> +    test "$xen" = "yes" || return 1
>> +    glob "$1" "*-softmmu" || return 1
>> +    case "${1%-softmmu}:$cpu" in
>> +        arm:arm | aarch64:aarch64 | \
>> +        i386:i386 | i386:x86_64 | x86_64:i386 | x86_64:x86_64)
> This again is claiming support for 64-bit guests with Xen on a
> 32-bit host, which AFAIK is impossible.

32-bit dom0 with 64-bit guests actually is not only possible, but also
widely used.

Paolo