[RFC PATCH] tests/qemuxml2*/graphics-spice-timeout: skip CPU model check

[Daniel Henrique Barboza]

On 11/17/21 07:51, Peter Krempa wrote:
> On Tue, Nov 16, 2021 at 21:11:50 -0300, Daniel Henrique Barboza wrote:
>> Commit 65b0b746b516 changed spice tests to use latest caps. Before this
>> change, "FLAG_REAL_CAPS" wasn't being set in testQemuInfoInitArgs(). The
>> absence of this flag triggered the code path inside
>> testCompareXMLToArgv() that executed testUpdateQEMUCaps(). This function
>> will update the host CPU via virQEMUCapsUpdateHostCPUModel() into
>> virQEMUCapsInitHostCPUModel().  In this function,
>> virQEMUCapsInitCPUModel() would end up updating the hostCPU inside the
>> qemuCaps (via virQEMUCapsProbeHostCPU()). Before the forementioned
>> commit, the host CPU was being defaulted to x86_64, vendor Intel, for
>> the 'graphics-spice-timeout' test that is using the 'pc' machine type
>> and 'accel=kvm'.
>>
>> Today, "FLAG_REAL_CAPS" is being set because we're using the latest caps
>> from x86_64. This means that the whole code path mentioned above is
>> skipped. qemuCaps are now being loaded via virQEMUCapsLoadCache()
>> directly.  Without the handling being done by testUpdateQEMUCaps(), the
>> host CPU is being retrieved later on, down below
>> qemuProcessCreatePretendCmdPrepare() into qemuProcessUpdateGuestCPU().
>> The latter will attempt to update the domain cpu and executing a
>> virCPUCompare with the hostCPU and def->cpu.
>>
>> All this logic ended up causing a failure of the
>> 'graphics-spice-timeout' test in ppc64 and s390x hosts. This test is
>> being run with KVM acceleration, and the KVM driver for ppc64 and s390x
>> will return a default x86_64 CPU with vendor "AMD", making
>> virCPUCompare() fail with the following message:
> 
> With all of this description which sounds plausible and pointing to the
> root cause of tests not being stable enough when used with real caps,
> the fix you are proposing seems to really just fix the symptom.
> 
> This patch itself is acceptable as is, but doesn't really fix the real
> issue. If you don't plan on addressing the root cause, please:


I'll wait to see if that fixes the problem Boris was experiencing with
s390x. Meanwhile I'll dig further to see if I can detect the root cause
of the problem (e.g. can we default to an Intel CPU instead of AMD).

> 
> 1) note in the commit message for this commit that it's not really
>     fixing the root cause, just the symptom
> 
> 2) file an upstream issue with your analysis so that we don't forget
>     that this is still broken

If I fail to fix the root cause in a sensible time I'll end up pushing this
patch - with the adjustments you suggested - to not let the tests being
broken for too long.

I'll file the bug shortly.


Thanks,


Daniel

> 
>> "QEMU XML-2-ARGV graphics-spice-timeout.x86_64-latest   ... libvirt: CPU
>> Driver error : the CPU is incompatible with host CPU: host CPU vendor does
>> not match required CPU vendor Intel"
>>
>> Fix this test by setting cpu check='none' and avoid the virCPUCompare()
>> that causes the problem for ppc64 and s390x hosts.
> 
> To resolve point 1), be more explicit that it's just a symptom fix in
> this sentence.
> 
>>
>> Reported-by: Boris Fiuczynski <fiuczy at linux.ibm.com>
>> Signed-off-by: Daniel Henrique Barboza <danielhb413 at gmail.com>
>> ---
>>
>> Sending as a RFC because I'm not sure if this patch fixes the
>> problem for s390x. Boris, can you please test and see if this
>> fix works for you?
> 
> It is plausible it will work, there are other cases which use
> match='exact' check='none' using real caps on X86 and they don't seem to
> be causing problems.
>