KVM: selftests: nSVM: Add enlightened MSR-Bitmap selftest

2022-02-10T18:50:48Z

Introduce a new test for Hyper-V nSVM extensions (Hyper-V on KVM) and add a test for enlightened MSR-Bitmap feature: - Intercept access to MSR_FS_BASE in L1 and check that this works with enlightened MSR-Bitmap disabled. - Enabled enlightened MSR-Bitmap and check that the intercept still works as expected. - Intercept access to MSR_GS_BASE but don't clear the corresponding bit from clean fields mask, KVM is supposed to skip updating MSR-Bitmap02 and thus the consequent access to the MSR from L2 will not get intercepted. - Finally, clear the corresponding bit from clean fields mask and check that access to MSR_GS_BASE is now intercepted. The test works with the assumption, that access to MSR_FS_BASE/MSR_GS_BASE is not intercepted for L1. If this ever becomes not true the test will fail as nested_svm_exit_handled_msr() always checks L1's MSR-Bitmap for L2 irrespective of clean fields. The behavior is correct as enlightened MSR-Bitmap feature is just an optimization, KVM is not obliged to ignore updates when the corresponding bit in clean fields stays clear. Signed-off-by: Vitaly Kuznetsov Message-Id: <20220203104620.277031-7-vkuznets@redhat.com> Signed-off-by: Paolo Bonzini

linux-dev/tools/testing/selftests/kvm/x86_64/hyperv_svm_test.c, branch linus/master

KVM: selftests: nSVM: Add enlightened MSR-Bitmap selftest