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[91.219.240.2]) by smtp.gmail.com with ESMTPSA id v1-20020a05620a440100b006fa2dde9db8sm4257678qkp.95.2022.11.01.09.27.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 01 Nov 2022 09:27:33 -0700 (PDT) From: Vitaly Kuznetsov To: Sean Christopherson Cc: kvm@vger.kernel.org, Paolo Bonzini , Wanpeng Li , Jim Mattson , Michael Kelley , Siddharth Chandrasekaran , Yuan Yao , Maxim Levitsky , linux-hyperv@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v13 45/48] KVM: selftests: Introduce rdmsr_from_l2() and use it for MSR-Bitmap tests In-Reply-To: References: <20221101145426.251680-1-vkuznets@redhat.com> <20221101145426.251680-46-vkuznets@redhat.com> Date: Tue, 01 Nov 2022 17:27:29 +0100 Message-ID: <87bkpqskr2.fsf@ovpn-194-149.brq.redhat.com> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Sean Christopherson 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 >> --- >> .../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