From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751824AbeC0Ekh (ORCPT ); Tue, 27 Mar 2018 00:40:37 -0400 Received: from userp2120.oracle.com ([156.151.31.85]:58936 "EHLO userp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751202AbeC0Ekg (ORCPT ); Tue, 27 Mar 2018 00:40:36 -0400 Date: Tue, 27 Mar 2018 00:40:20 -0400 From: Konrad Rzeszutek Wilk To: Wanpeng Li Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Paolo Bonzini , Radim =?utf-8?B?S3LEjW3DocWZ?= , Andrew Cooper Subject: Re: [PATCH 2/2] KVM: VMX: Add Force Emulation Prefix for "emulate the next instruction" Message-ID: <20180327044020.GB16974@char.us.oracle.com> References: <1522116735-4861-1-git-send-email-wanpengli@tencent.com> <1522116735-4861-3-git-send-email-wanpengli@tencent.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <1522116735-4861-3-git-send-email-wanpengli@tencent.com> User-Agent: Mutt/1.8.3 (2017-05-23) X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=8844 signatures=668695 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1711220000 definitions=main-1803270044 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by mail.home.local id w2R4egle027959 On Mon, Mar 26, 2018 at 07:12:15PM -0700, Wanpeng Li wrote: > From: Wanpeng Li > > This patch introduces a Force Emulation Prefix (ud2a; .ascii "kvm") for > "emulate the next instruction", the codes will be executed by emulator > instead of processor, for testing purposes. Can you expand a bit ? Why do you want this in KVM in the first place? Should this be controlled by a boolean parameter? > > A testcase here: > > #include > #include > > #define HYPERVISOR_INFO 0x40000000 > > #define CPUID(idx, eax, ebx, ecx, edx)\ > asm volatile (\ > "ud2a; .ascii \"kvm\"; 1: cpuid" \ > :"=b" (*ebx), "=a" (*eax),"=c" (*ecx), "=d" (*edx)\ > :"0"(idx) ); > > void main() > { > unsigned int eax,ebx,ecx,edx; > char string[13]; > > CPUID(HYPERVISOR_INFO, &eax, &ebx, &ecx, &edx); > *(unsigned int *)(string+0) = ebx; > *(unsigned int *)(string+4) = ecx; > *(unsigned int *)(string+8) = edx; > > string[12] = 0; > if (strncmp(string, "KVMKVMKVM\0\0\0",12) == 0) > printf("kvm guest\n"); > else > printf("bare hardware\n"); > } > > Suggested-by: Andrew Cooper > Cc: Paolo Bonzini > Cc: Radim Krčmář > Cc: Andrew Cooper > Signed-off-by: Wanpeng Li > --- > arch/x86/kvm/vmx.c | 18 +++++++++++++++++- > 1 file changed, 17 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c > index 0f99833..90abed8 100644 > --- a/arch/x86/kvm/vmx.c > +++ b/arch/x86/kvm/vmx.c > @@ -108,6 +108,9 @@ module_param_named(enable_shadow_vmcs, enable_shadow_vmcs, bool, S_IRUGO); > static bool __read_mostly nested = 0; > module_param(nested, bool, S_IRUGO); > > +static bool __read_mostly fep = 0; > +module_param(fep, bool, S_IRUGO); > + > static u64 __read_mostly host_xss; > > static bool __read_mostly enable_pml = 1; > @@ -6218,8 +6221,21 @@ static int handle_machine_check(struct kvm_vcpu *vcpu) > static int handle_ud(struct kvm_vcpu *vcpu) > { > enum emulation_result er; > + int emulation_type = EMULTYPE_TRAP_UD; > + > + if (fep) { > + char sig[5]; /* ud2; .ascii "kvm" */ > + struct x86_exception e; Don't you want to do = { }; to memset it? > + > + kvm_read_guest_virt(&vcpu->arch.emulate_ctxt, > + kvm_get_linear_rip(vcpu), sig, sizeof(sig), &e); > + if (memcmp(sig, "\xf\xbkvm", sizeof(sig)) == 0) { > + emulation_type = 0; > + kvm_rip_write(vcpu, kvm_rip_read(vcpu) + sizeof(sig)); > + } > + } > > - er = emulate_instruction(vcpu, EMULTYPE_TRAP_UD); > + er = emulate_instruction(vcpu, emulation_type); > if (er == EMULATE_USER_EXIT) > return 0; > if (er != EMULATE_DONE) > -- > 2.7.4 >