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([2001:b07:6468:f312:a0f7:472a:1e7:7ef]) by smtp.gmail.com with ESMTPSA id d13sm15611356wrq.51.2019.11.11.06.08.13 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 11 Nov 2019 06:08:14 -0800 (PST) Subject: Re: [PATCH] KVM: X86: avoid unused setup_syscalls_segments call when SYSCALL check failed To: linmiaohe , rkrcmar@redhat.com, sean.j.christopherson@intel.com, vkuznets@redhat.com, wanpengli@tencent.com, jmattson@google.com, joro@8bytes.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, hpa@zytor.com Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, x86@kernel.org References: <1573289934-14430-1-git-send-email-linmiaohe@huawei.com> From: Paolo Bonzini Openpgp: preference=signencrypt Message-ID: <37dcc0bb-b624-4ea2-976a-51f5bfbd81a6@redhat.com> Date: Mon, 11 Nov 2019 15:08:16 +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: <1573289934-14430-1-git-send-email-linmiaohe@huawei.com> Content-Language: en-US X-MC-Unique: UMH25rTiOz6KQd29kwUtLA-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 On 09/11/19 09:58, linmiaohe wrote: > From: Miaohe Lin >=20 > When SYSCALL/SYSENTER ability check failed, cs and ss is inited but > remain not used. Delay initializing cs and ss until SYSCALL/SYSENTER > ability check passed. >=20 > Signed-off-by: Miaohe Lin > --- > arch/x86/kvm/emulate.c | 6 ++---- > 1 file changed, 2 insertions(+), 4 deletions(-) >=20 > diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c > index 698efb8c3897..952d1a4f4d7e 100644 > --- a/arch/x86/kvm/emulate.c > +++ b/arch/x86/kvm/emulate.c > @@ -2770,11 +2770,10 @@ static int em_syscall(struct x86_emulate_ctxt *ct= xt) > =09=09return emulate_ud(ctxt); > =20 > =09ops->get_msr(ctxt, MSR_EFER, &efer); > -=09setup_syscalls_segments(ctxt, &cs, &ss); > - > =09if (!(efer & EFER_SCE)) > =09=09return emulate_ud(ctxt); > =20 > +=09setup_syscalls_segments(ctxt, &cs, &ss); > =09ops->get_msr(ctxt, MSR_STAR, &msr_data); > =09msr_data >>=3D 32; > =09cs_sel =3D (u16)(msr_data & 0xfffc); > @@ -2838,12 +2837,11 @@ static int em_sysenter(struct x86_emulate_ctxt *c= txt) > =09if (ctxt->mode =3D=3D X86EMUL_MODE_PROT64) > =09=09return X86EMUL_UNHANDLEABLE; > =20 > -=09setup_syscalls_segments(ctxt, &cs, &ss); > - > =09ops->get_msr(ctxt, MSR_IA32_SYSENTER_CS, &msr_data); > =09if ((msr_data & 0xfffc) =3D=3D 0x0) > =09=09return emulate_gp(ctxt, 0); > =20 > +=09setup_syscalls_segments(ctxt, &cs, &ss); > =09ctxt->eflags &=3D ~(X86_EFLAGS_VM | X86_EFLAGS_IF); > =09cs_sel =3D (u16)msr_data & ~SEGMENT_RPL_MASK; > =09ss_sel =3D cs_sel + 8; >=20 Queued, thanks. Paolo