Re: [PATCH RESEND v7 9/9] tests/qtest: Fix tests when no KVM or TCG are present

["Alex Bennée" <alex.bennee@linaro.org>]

Fabiano Rosas <farosas@suse.de> writes:

> Juan Quintela <quintela@redhat.com> writes:
>
>> Fabiano Rosas <farosas@suse.de> wrote:
>>> It is possible to have a build with both TCG and KVM disabled due to
>>> Xen requiring the i386 and x86_64 binaries to be present in an aarch64
>>> host.
>>
>> Ouch.
>>
>> Just curious: why are they needed?
>>
>
> From https://wiki.xenproject.org/wiki/QEMU_Upstream:
>
>   Why is qemu-system-i386 used even on x86_64 and even non-x86?
>   
>   QEMU in a Xen system only provides device model (DM) emulation and not
>   any CPU instruction emulation, so the nominal arch doesn't actually
>   matter and Xen builds i386 everywhere as a basically arbitrary choice.
>   
>   It happens that the Xen DM part of QEMU is quite closely tied to the x86
>   scaffolding for various historical reasons, so we end up using
>   qemu-system-i386 even e.g. on ARM!  There is no practical difference
>   between qemu-system-i386 and qemu-system-x86_64, they should be
>   interchangeable. However only qemu-system-i386 is regularly tested by
>   Xen Project (via osstest).

That said with the xenpvh model that was added recently we should be
able to finally build a Xen only qemu-system-aarch64 which while
functionally the same will be less head scratching for users.

>
>>>
>>> If we build with --disable-tcg on the aarch64 host, we will end-up
>>> with a QEMU binary (x86) that does not support TCG nor KVM.
>>>
>>> Fix tests that crash or hang in the above scenario. Do not include any
>>> test cases if TCG and KVM are missing.
>>>
>>> Signed-off-by: Fabiano Rosas <farosas@suse.de>
>>> ---
>>> This currently affects Arm, but will also affect x86 after the xenpvh
>>> series gets merged. This patch fixes both scenarios.
>>
>> Reviewed-by: Juan Quintela <quintela@redhat.com>
>
> Thanks!


-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro