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([2001:b07:6468:f312:a15b:f753:1ac4:56dc]) by smtp.gmail.com with ESMTPSA id z14sm6685230wrl.60.2019.11.14.03.58.55 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 14 Nov 2019 03:58:55 -0800 (PST) Subject: Re: [PATCH 1/2] KVM: X86: Single target IPI fastpath To: Wanpeng Li , linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel References: <1573283135-5502-1-git-send-email-wanpengli@tencent.com> From: Paolo Bonzini Message-ID: <6c2c7bbb-39f4-2a77-632e-7730e9887fc5@redhat.com> Date: Thu, 14 Nov 2019 12:58:56 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <1573283135-5502-1-git-send-email-wanpengli@tencent.com> Content-Language: en-US X-MC-Unique: XuyUh46nMr2DVtIprUzxTg-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Ok, it's not _so_ ugly after all. > --- > arch/x86/kvm/vmx/vmx.c | 39 +++++++++++++++++++++++++++++++++++++-- > include/linux/kvm_host.h | 1 + > 2 files changed, 38 insertions(+), 2 deletions(-) >=20 > diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c > index 5d21a4a..5c67061 100644 > --- a/arch/x86/kvm/vmx/vmx.c > +++ b/arch/x86/kvm/vmx/vmx.c > @@ -5924,7 +5924,9 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu) > =09=09} > =09} > =20 > -=09if (exit_reason < kvm_vmx_max_exit_handlers > +=09if (vcpu->fast_vmexit) > +=09=09return 1; > +=09else if (exit_reason < kvm_vmx_max_exit_handlers Instead of a separate vcpu->fast_vmexit, perhaps you can set exit_reason to vmx->exit_reason to -1 if the fast path succeeds. > +=09=09=09if (ret =3D=3D 0) > +=09=09=09=09ret =3D kvm_skip_emulated_instruction(vcpu); Please move the "kvm_skip_emulated_instruction(vcpu)" to vmx_handle_exit, so that this basically is #define EXIT_REASON_NEED_SKIP_EMULATED_INSN -1 =09if (ret =3D=3D 0) =09=09vcpu->exit_reason =3D EXIT_REASON_NEED_SKIP_EMULATED_INSN; and handle_ipi_fastpath can return void. Thanks, Paolo > +=09=09}; > +=09}; > + > +=09return ret; > +} > + > static void vmx_vcpu_run(struct kvm_vcpu *vcpu) > { > =09struct vcpu_vmx *vmx =3D to_vmx(vcpu); > @@ -6615,6 +6645,12 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu) > =09=09=09=09 | (1 << VCPU_EXREG_CR3)); > =09vcpu->arch.regs_dirty =3D 0; > =20 > +=09vmx->exit_reason =3D vmx->fail ? 0xdead : vmcs_read32(VM_EXIT_REASON)= ; > +=09vcpu->fast_vmexit =3D false; > +=09if (!is_guest_mode(vcpu) && > +=09=09vmx->exit_reason =3D=3D EXIT_REASON_MSR_WRITE) > +=09=09vcpu->fast_vmexit =3D handle_ipi_fastpath(vcpu); This should be done later, at least after kvm_put_guest_xcr0, because running with partially-loaded guest state is harder to audit. The best place to put it actually is right after the existing vmx->exit_reason assignment, where we already handle EXIT_REASON_MCE_DURING_VMENTRY. > =09pt_guest_exit(vmx); > =20 > =09/* > @@ -6634,7 +6670,6 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu) > =09vmx->nested.nested_run_pending =3D 0; > =09vmx->idt_vectoring_info =3D 0; > =20 > -=09vmx->exit_reason =3D vmx->fail ? 0xdead : vmcs_read32(VM_EXIT_REASON)= ; > =09if ((u16)vmx->exit_reason =3D=3D EXIT_REASON_MCE_DURING_VMENTRY) > =09=09kvm_machine_check(); > =20 > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h > index 719fc3e..7a7358b 100644 > --- a/include/linux/kvm_host.h > +++ b/include/linux/kvm_host.h > @@ -319,6 +319,7 @@ struct kvm_vcpu { > #endif > =09bool preempted; > =09bool ready; > +=09bool fast_vmexit; > =09struct kvm_vcpu_arch arch; > =09struct dentry *debugfs_dentry; > }; >=20