David Matlack recently added a feature known as eager page splitting to x86 KVM. This feature improves vCPU performance during dirty logging because the splitting operation is moved out of the page fault path, avoiding EPT/NPT violations or allowing the vCPU threads to resolve the violation in the fast path. While this feature is a great performance improvement, it does not have adequate testing in KVM selftests. Add a test to provide coverage of eager page splitting. Patch 1 is a quick refactor to be able to re-use some code from dirty_log_perf_test. Patch 2 adds the actual test. V4->V5: - V4: https://lore.kernel.org/all/Y9lIfGtMEEsaw6cd@xxxxxxxxxx/ - Separated a helper function to just run vCPUs for an iteration and not also collect the stats. Suggested by Vipin. - Added a log message when the host does not support MANUAL_PROTECT, and so testing with that capability is skipped. Also suggested by Vipin. - Added RB from Vipin. V3->V4: - Added the copyright notices back. Thanks Vipin for the right thing to do there. V2->V3: - Removed copyright notice from the top of dirty_log_page_splitting.c - Adopted ASSERT_EQ for test assertions - Now skipping testing with MANUAL_PROTECT if unsupported V1->V2: - Run test in multiple modes, as suggested by David and Ricardo - Cleanups from shameful copy-pasta, as suggested by David Ben Gardon (2): selftests: KVM: Move dirty logging functions to memstress.(c|h) selftests: KVM: Add dirty logging page splitting test tools/testing/selftests/kvm/Makefile | 1 + .../selftests/kvm/dirty_log_perf_test.c | 84 +----- .../selftests/kvm/include/kvm_util_base.h | 1 + .../testing/selftests/kvm/include/memstress.h | 8 + tools/testing/selftests/kvm/lib/kvm_util.c | 5 + tools/testing/selftests/kvm/lib/memstress.c | 72 +++++ .../x86_64/dirty_log_page_splitting_test.c | 260 ++++++++++++++++++ 7 files changed, 354 insertions(+), 77 deletions(-) create mode 100644 tools/testing/selftests/kvm/x86_64/dirty_log_page_splitting_test.c -- 2.39.1.456.gfc5497dd1b-goog
