Re: [RFC 0/3] qtest: pick tests that require KVM at runtime

From: Thomas Huth <thuth@redhat.com>
To: "Philippe Mathieu-Daudé" <philmd@redhat.com>,
	"Igor Mammedov" <imammedo@redhat.com>,
	qemu-devel@nongnu.org
Cc: lvivier@redhat.com, mst@redhat.com
Subject: Re: [RFC 0/3] qtest: pick tests that require KVM at runtime
Date: Tue, 22 Jun 2021 09:59:48 +0200	[thread overview]
Message-ID: <bb1b17d4-6da5-aebf-329a-905dd566ec6b@redhat.com> (raw)
In-Reply-To: <75263d99-5da8-bdc5-e977-13c83a31b532@redhat.com>

On 22/06/2021 09.26, Philippe Mathieu-Daudé wrote:
> On 6/22/21 9:20 AM, Thomas Huth wrote:
>> On 16/06/2021 17.24, Igor Mammedov wrote:
>>>
>>> Sometimes it's necessary to execute a test that depends on KVM,
>>> however qtest is not aware if tested QEMU binary supports KVM
>>> on the host it the test is executed.
>>>
>>> For an example:
>>>    test q35 machine with intel_iommu
>>>    This test will run only is KVM is available and fail
>>>    to start QEMU if it fallsback to TCG, thus failing whole test.
>>>    So if test is executed in VM where nested KVM is not enabled
>>>    or on other than x86 host, it will break 'make check-qtest'
>>>
>>> Series adds a lightweight qtest_has_kvm() check, which abuses
>>> build system and should help to avoid running KVM only tests
>>> on hosts that do not support it.
>>
>> You also might want to update the check in tests/qtest/migration-test.c
>> while you're at it.
>>
>>> PS:
>>> there is an alternative 'query-accels' QMP command proposal
>>> https://patchwork.kernel.org/project/qemu-devel/patch/20210503211020.894589-3-philmd@redhat.com/
>>>
>>> which I think is more robust compared to qtest_has_kvm() and
>>> could be extended to take into account machine type.
>>
>> Could you please get in touch with Philippe directly and discuss which
>> way to go? We certainly don't need two approaches in the end...
> 
> I'm certainly fine if Igor wants to restart this effort :)
> 
> Maybe doing as Claudio suggested, start have qtest_has_accel()
> tests accel with Igor's shortpath first, then fallback to
> 'query-accels' QMP command?

Yeah, that's maybe a good idea ...
But I'm currently wondering whether we need query-accels at all? For 
detecting kvm, we already have "query-kvm" ... and we don't have tests for 
any other accelerators yet (hax, hvf, etc.) ... so it's likely just about 
having a way to detect whether TCG is compiled into the binary? Is there 
already another command that could be used to check for the availability of TCG?

  Thomas