selftests: kvm: irqfd_test: KVM_IRQFD failed, rc: -1 errno: 11 (Resource temporarily unavailable)

selftests: kvm: irqfd_test: KVM_IRQFD failed, rc: -1 errno: 11 (Resource temporarily unavailable)

[Naresh Kamboju]

The selftests: kvm: irqfd_test consistently fails across all test platforms
since its introduction in Linux next-20250625. The failure occurs due to
a KVM_IRQFD ioctl returning errno 11 (Resource temporarily unavailable).
This has been observed from day one and is reproducible on all test runs.

Reproducibility: 100% failure on all test platforms since
next-20250625..next-20250929

Test fails on the below list
 * graviton4
 * rk3399-rock-pi-4b

## Initial Observations:
The test is attempting to register an IRQFD but fails with EAGAIN (errno 11).
This likely indicates resource exhaustion or unsupported behavior on
affected ARM-based platforms.

Could you please advise on the way forward for this test?
Should we treat this as an unsupported case on ARM platforms,
or is there a missing implementation/configuration that needs to be addressed?

## Test log
selftests: kvm: irqfd_test
Random seed: 0x6b8b4567
==== Test Assertion Failure ====
  include/kvm_util.h:527: !ret
  pid=721 tid=721 errno=11 - Resource temporarily unavailable
     1 0x000000000040250f: kvm_irqfd at kvm_util.h:527
     2 0x000000000040222f: main at irqfd_test.c:100
     3 0x0000ffffbd43229b: ?? ??:0
     4 0x0000ffffbd43237b: ?? ??:0
addr2line:      5 0x000000000040206f: DWARF error: mangled line number
section (bad file number)
addr2line: DWARF error: mangled line number section (bad file number)
_start at ??:?
  KVM_IRQFD failed, rc: -1 errno: 11 (Resource temporarily unavailable)
not ok 4 selftests: kvm: irqfd_test exit=254

## Links
   * https://qa-reports.linaro.org/lkft/linux-next-master/build/next-20250929/testrun/30048394/suite/kselftest-kvm/test/kvm_irqfd_test/log
   * https://qa-reports.linaro.org/lkft/linux-next-master/build/next-20250929/testrun/30048394/suite/kselftest-kvm/test/kvm_irqfd_test/details/

Re: selftests: kvm: irqfd_test: KVM_IRQFD failed, rc: -1 errno: 11 (Resource temporarily unavailable)

[Sean Christopherson]

On Tue, Sep 30, 2025, Naresh Kamboju wrote:
> The selftests: kvm: irqfd_test consistently fails across all test platforms
> since its introduction in Linux next-20250625. The failure occurs due to
> a KVM_IRQFD ioctl returning errno 11 (Resource temporarily unavailable).
> This has been observed from day one and is reproducible on all test runs.

It's a known issue[*], that I think we kinda forgot about.  The underlying issue
is that KVM ARM needs the test to create a vGIC, but the fix stalled out a bit
because there isn't one single, "obviously correct" way to do that.

I'll Cc you and ping Oliver on the other thread.

[*] https://lore.kernel.org/all/20250825155203.71989-1-sebott@redhat.com