On Thu, Jun 13, 2024, Maxim Levitsky wrote: > Hi! > > This kvm unit test tests that all reserved bits of the MSR_IA32_FLUSH_CMD #GP, but apparently > on some systems this test fails. > > For example I reproduced this on: > > model name : Intel(R) Xeon(R) CPU E3-1260L v5 @ 2.90GHz > stepping : 3 > microcode : 0xf0 > > > As I see in the 'vmx_vcpu_after_set_cpuid', we passthough this msr to the guest AS IS, > thus the unit test tests the microcode. > > So I suspect that the test actually caught a harmless microcode bug. Yeah, we encountered the same thing and came to the same conclusion. > What do you think we should do to workaround this? Maybe disable this check on > affected cpus or turn it into a warning because MSR_IA32_FLUSH_CMD reserved bits > test doesn't test KVM? Ya, Mingwei posted a patch[*] to force KVM to emulate the faulting accesses, which more or less does exactly that, but preserves a bit of KVM coverage. I'll get a KUT pull request sent to Paolo today, I've got a sizeable number of changes ready. [*] https://lore.kernel.org/all/20240417232906.3057638-3-mizhang@xxxxxxxxxx
