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[213.175.37.10]) by smtp.gmail.com with ESMTPSA id x5sm19529043wrg.69.2019.09.23.02.31.59 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 23 Sep 2019 02:31:59 -0700 (PDT) From: Vitaly Kuznetsov To: Andrea Arcangeli , Paolo Bonzini Cc: "Dr. David Alan Gilbert" , Marcelo Tosatti , Peter Xu , kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 15/17] KVM: retpolines: x86: eliminate retpoline from vmx.c exit handlers In-Reply-To: <20190920212509.2578-16-aarcange@redhat.com> References: <20190920212509.2578-1-aarcange@redhat.com> <20190920212509.2578-16-aarcange@redhat.com> Date: Mon, 23 Sep 2019 11:31:58 +0200 Message-ID: <87o8zb8ik1.fsf@vitty.brq.redhat.com> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Andrea Arcangeli writes: > It's enough to check the exit value and issue a direct call to avoid > the retpoline for all the common vmexit reasons. > > Signed-off-by: Andrea Arcangeli > --- > arch/x86/kvm/vmx/vmx.c | 24 ++++++++++++++++++++++-- > 1 file changed, 22 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c > index a6e597025011..9aa73e216df2 100644 > --- a/arch/x86/kvm/vmx/vmx.c > +++ b/arch/x86/kvm/vmx/vmx.c > @@ -5866,9 +5866,29 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu) > } > > if (exit_reason < kvm_vmx_max_exit_handlers > - && kvm_vmx_exit_handlers[exit_reason]) > + && kvm_vmx_exit_handlers[exit_reason]) { > +#ifdef CONFIG_RETPOLINE > + if (exit_reason == EXIT_REASON_MSR_WRITE) > + return handle_wrmsr(vcpu); > + else if (exit_reason == EXIT_REASON_PREEMPTION_TIMER) > + return handle_preemption_timer(vcpu); > + else if (exit_reason == EXIT_REASON_PENDING_INTERRUPT) > + return handle_interrupt_window(vcpu); > + else if (exit_reason == EXIT_REASON_EXTERNAL_INTERRUPT) > + return handle_external_interrupt(vcpu); > + else if (exit_reason == EXIT_REASON_HLT) > + return handle_halt(vcpu); > + else if (exit_reason == EXIT_REASON_PAUSE_INSTRUCTION) > + return handle_pause(vcpu); > + else if (exit_reason == EXIT_REASON_MSR_READ) > + return handle_rdmsr(vcpu); > + else if (exit_reason == EXIT_REASON_CPUID) > + return handle_cpuid(vcpu); > + else if (exit_reason == EXIT_REASON_EPT_MISCONFIG) > + return handle_ept_misconfig(vcpu); > +#endif > return kvm_vmx_exit_handlers[exit_reason](vcpu); I agree with the identified set of most common vmexits, however, this still looks a bit random. Would it be too much if we get rid of kvm_vmx_exit_handlers completely replacing this code with one switch()? > - else { > + } else { > vcpu_unimpl(vcpu, "vmx: unexpected exit reason 0x%x\n", > exit_reason); > dump_vmcs(); -- Vitaly