[0/4] KVM: selftests: dirty_log_test: fixes for running the test nested

Message

Maxim Levitsky Dec. 11, 2024, 7:37 p.m. UTC

As a part of the effort to start running kvm selftests nested, this patch
series contains several fixes to the dirty_log_test, which allows this test
to run nested very well.

I also included a mostly nop change to KVM, to reverse the order in which
the PML log is read to align more closely to the hardware. It should
not affect regular users of the dirty logging but it fixes a unit test
specific assumption in the dirty_log_test dirty-ring mode.

Patch 4 fixes a very rare problem, which is hard to reproduce with standard
test parameters, but due to some weird timing issue, it
actually happened a few times on my machine which prompted me to investigate
it.

The issue can be reproduced well by running the test nested
(without patch 4 applied) with a very short iteration time and with a
few iterations in a loop like this:

while ./dirty_log_test -i 10 -I 1 -M dirty-ring ; do true ; done

Or even better, it's possible to manually patch the test to not wait at all
(effectively setting iteration time to 0), then it fails pretty fast.

Best regards,
       Maxim Levitsky

Maxim Levitsky (4):
  KVM: VMX: read the PML log in the same order as it was written
  KVM: selftests: dirty_log_test: Limit s390x workaround to s390x
  KVM: selftests: dirty_log_test: run the guest until some dirty ring
    entries were harvested
  KVM: selftests: dirty_log_test: support multiple write retires

 arch/x86/kvm/vmx/vmx.c                       | 32 +++++---
 arch/x86/kvm/vmx/vmx.h                       |  1 +
 tools/testing/selftests/kvm/dirty_log_test.c | 79 +++++++++++++++++---
 3 files changed, 91 insertions(+), 21 deletions(-)