Re: [RFC kvm-unit-tests PATCH 4/4] x86/apic: Add test for xapic-split

[Sean Christopherson <seanjc@google.com>]

On Tue, Feb 25, 2025, Naveen N Rao (AMD) wrote:
> The current apic-split test actually uses x2apic. Rename the same, and
> add a separate test for xapic in split irqchip mode.

I would actually prefer we go in the opposite direction and rip out the testcases
that explicitly specify kernel_irqchip=split, not add more.  And instead either
defer to the user via ACCEL=, or make it a top-level switch.

While it would be nice for unittests.cfg to cover more scenarios by "default",
the flip side of doing so is that makes it annoying for an end user to do more,
and gives the false impression that the configurations in unittests.cfg are the
only ones that are worth testing.

E.g. svm_npt fails with kernel_irqchip=split on x2AVIC hardware due to test bugs
(patches incoming), hyperv_connections fails due to what is effectively a
QEMU bug that also got hoisted into KVM[1], and vmx_apic_passthrough_tpr_threshold_test
also fails with kernel_irqchip=split due to a KVM bug that happened to be masked
by another KVM bug with the in-kernel PIT emulation.

[1] https://lore.kernel.org/all/Z8ZBzEJ7--VWKdWd@google.com
[2] https://lore.kernel.org/all/202502271500.28201544-lkp@intel.com