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

[Claudio Fontana]

On 6/18/21 1:26 PM, Igor Mammedov wrote:
> On Thu, 17 Jun 2021 18:49:17 +0200
> Claudio Fontana <cfontana@suse.de> wrote:
> 
>> On 6/16/21 5:24 PM, 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.  
>>
>> Hello,
>>
>> It seems to me that we are constantly re-implementing the same feature with 
>> slight variations?
>>
>> Didn't we have a generic series to introduce qtest_has_accel() from Philippe 
>> before?
> It's mentioned in cover letter (PS: part) and in [1/3] with rationale
> why this was posted.

Thought it was separate, but now I see that it uses query-accel underneath.

Seems strange to add another check to do the same thing, it may point to 
qtest_has_accel() needing some update?
You mention it is time consuming to use qtest_has_accel(), have you measured an 
important overhead?
With qtest_has_accel() not even being committed yet, is it already necessary to 
work around it because it's too slow? 
 
> 
>> Does this series work with --disable-kvm builds? (TCG-only builds?)
> I'll test. But on the first glance it should work without issues.
> (i.e. kvm only tests will be skipped).
> 
>>
>> Thanks,
>>
>> CLaudio
>>
>>
>>>
>>> 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.
>>>
>>> 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.
>>> But it's more complex and what I dislike about it most,
>>> it requires execution of 'probing' QEMU instance to find
>>> execute 'query-accels' QMP command, which is rather resource
>>> consuming. So I'd use query-accels approach only when it's
>>> the only possible option to minimize load on CI systems.
>>>
>>> Igor Mammedov (2):
>>>   tests: acpi: q35: test for x2APIC entries in SRAT
>>>   tests: acpi: update expected tables blobs
>>>
>>> root (1):
>>>   tests: qtest: add qtest_has_kvm() to check if tested bynary supports
>>>     KVM
>>>
>>>  tests/qtest/libqos/libqtest.h    |   7 +++++++
>>>  meson.build                      |   1 +
>>>  tests/data/acpi/q35/APIC.numamem | Bin 0 -> 2686 bytes
>>>  tests/data/acpi/q35/DSDT.numamem | Bin 7865 -> 35222 bytes
>>>  tests/data/acpi/q35/FACP.numamem | Bin 0 -> 244 bytes
>>>  tests/data/acpi/q35/SRAT.numamem | Bin 224 -> 5080 bytes
>>>  tests/qtest/bios-tables-test.c   |  10 +++++++---
>>>  tests/qtest/libqtest.c           |  20 ++++++++++++++++++++
>>>  8 files changed, 35 insertions(+), 3 deletions(-)
>>>  create mode 100644 tests/data/acpi/q35/APIC.numamem
>>>  create mode 100644 tests/data/acpi/q35/FACP.numamem
>>>   
>>
>