Sean Christopherson <seanjc@xxxxxxxxxx> writes: > On Tue, Nov 01, 2022, Vitaly Kuznetsov wrote: >> Hyper-V MSR-Bitmap tests do RDMSR from L2 to exit to L1. While 'evmcs_test' >> correctly clobbers all GPRs (which are not preserved), 'hyperv_svm_test' >> does not. Introduce and use common rdmsr_from_l2() to avoid code >> duplication and remove hardcoding of MSRs. >> >> Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx> >> --- >> .../selftests/kvm/include/x86_64/processor.h | 9 +++++++ >> .../testing/selftests/kvm/x86_64/evmcs_test.c | 24 ++++--------------- >> .../selftests/kvm/x86_64/hyperv_svm_test.c | 8 +++---- >> 3 files changed, 17 insertions(+), 24 deletions(-) >> >> diff --git a/tools/testing/selftests/kvm/include/x86_64/processor.h b/tools/testing/selftests/kvm/include/x86_64/processor.h >> index fbaf0b6cec4b..a14b7e4ea7c4 100644 >> --- a/tools/testing/selftests/kvm/include/x86_64/processor.h >> +++ b/tools/testing/selftests/kvm/include/x86_64/processor.h >> @@ -520,6 +520,15 @@ static inline void cpu_relax(void) >> "hlt\n" \ >> ) >> >> +/* Exit to L1 from L2 with RDMSR instruction */ >> +static inline void rdmsr_from_l2(uint32_t msr) > > I would prefer keeping this helper out of common x86-64 code, even if it means > duplicating code across multiple Hyper-V tests until the L1 VM-Enter/VM-Exit > sequences get cleaned up. The name is misleading, e.g. it doesn't really read > the MSR since there are no outputs It's somewhat similar to vmcall()/vmmcall() which are only used to exit from L2 to L1 (and thus nobody complained that all the register values are random) and not issue a hypercall and return some value. > and while we could obviously fix that with a > rename or a generic DO_VMEXIT_FROM_L2() macro, I would rather fix the underlying > problem of the world switches clobbering L2 state. That way all the helpers that > exist for L1 can be used verbatim for L2 instead of needing dedicated helpers for > every instruction that is used to trigger a VM-Exit. > I'm fine with keeping two copies of this in Hyper-V tests for now, of course. -- Vitaly
