Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754672AbaFRTJW (ORCPT ); Wed, 18 Jun 2014 15:09:22 -0400 Received: from mx1.redhat.com ([209.132.183.28]:44771 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754253AbaFRTJU (ORCPT ); Wed, 18 Jun 2014 15:09:20 -0400 From: Bandan Das To: "Gabriel L. Somlo" Cc: Eric Northup , Nadav Amit , Paolo Bonzini , gleb@kernel.org, Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , the arch/x86 maintainers , Linux Kernel Mailing List , KVM , joro@8bytes.org, mst@redhat.com, agraf@suse.de Subject: Re: [PATCH 3/3] KVM: x86: correct mwait and monitor emulation References: <20140618184601.GE1695@ERROL.INI.CMU.EDU> Date: Wed, 18 Jun 2014 15:09:00 -0400 Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.3 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org "Gabriel L. Somlo" writes: > On Wed, Jun 18, 2014 at 10:59:14AM -0700, Eric Northup wrote: >> On Wed, Jun 18, 2014 at 7:19 AM, Nadav Amit wrote: >> > mwait and monitor are currently handled as nop. Considering this behavior, they >> > should still be handled correctly, i.e., check execution conditions and generate >> > exceptions when required. mwait and monitor may also be executed in real-mode >> > and are not handled in that case. This patch performs the emulation of >> > monitor-mwait according to Intel SDM (other than checking whether interrupt can >> > be used as a break event). >> > >> > Signed-off-by: Nadav Amit > > How about this instead (details in the commit log below) ? Please let > me know what you think, and if you'd prefer me to send it out as a > separate patch rather than a reply to this thread. I am not saying we should "punish" guests that don't do the right thing. But if we can't emulate it the right way, we emulate it ? And the fact that a workaround exists for the guest is all the more better :) > Thanks, > --Gabriel > > > From 0375a0aceb54cdbc26a6c0e5b43c46324f830ec3 Mon Sep 17 00:00:00 2001 > From: "Gabriel L. Somlo" > Date: Wed, 18 Jun 2014 14:39:15 -0400 > Subject: [PATCH] kvm: x86: revert "emulate monitor and mwait instructions as nop" > > This reverts commit 87c00572ba05aa8c9db118da75c608f47eb10b9e. > > OS X <= 10.7.* are the only known guests which realistically required > this functionality. As it turns out, OS X can be told to forego using > monitor/mwait by passing it "idlehalt=0" as a kernel argument, so we're > better off removing this hack from KVM altogether. > > Signed-off-by: Gabriel L. Somlo > --- > arch/x86/kvm/cpuid.c | 2 -- > arch/x86/kvm/svm.c | 8 +++----- > arch/x86/kvm/vmx.c | 10 ++++------ > 3 files changed, 7 insertions(+), 13 deletions(-) > > diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c > index 38a0afe..17b42fa 100644 > --- a/arch/x86/kvm/cpuid.c > +++ b/arch/x86/kvm/cpuid.c > @@ -283,8 +283,6 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function, > 0 /* Reserved */ | f_lm | F(3DNOWEXT) | F(3DNOW); > /* cpuid 1.ecx */ > const u32 kvm_supported_word4_x86_features = > - /* NOTE: MONITOR (and MWAIT) are emulated as NOP, > - * but *not* advertised to guests via CPUID ! */ > F(XMM3) | F(PCLMULQDQ) | 0 /* DTES64, MONITOR */ | > 0 /* DS-CPL, VMX, SMX, EST */ | > 0 /* TM2 */ | F(SSSE3) | 0 /* CNXT-ID */ | 0 /* Reserved */ | > diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c > index ec8366c..0e8ef20 100644 > --- a/arch/x86/kvm/svm.c > +++ b/arch/x86/kvm/svm.c > @@ -3274,7 +3274,7 @@ static int pause_interception(struct vcpu_svm *svm) > return 1; > } > > -static int nop_interception(struct vcpu_svm *svm) > +static int invalid_op_interception(struct vcpu_svm *svm) > { > skip_emulated_instruction(&(svm->vcpu)); > return 1; > @@ -3282,14 +3282,12 @@ static int nop_interception(struct vcpu_svm *svm) > > static int monitor_interception(struct vcpu_svm *svm) > { > - printk_once(KERN_WARNING "kvm: MONITOR instruction emulated as NOP!\n"); > - return nop_interception(svm); > + return invalid_op_interception(svm); > } > > static int mwait_interception(struct vcpu_svm *svm) > { > - printk_once(KERN_WARNING "kvm: MWAIT instruction emulated as NOP!\n"); > - return nop_interception(svm); > + return invalid_op_interception(svm); > } > > static int (*const svm_exit_handlers[])(struct vcpu_svm *svm) = { > diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c > index 801332e..577c7df 100644 > --- a/arch/x86/kvm/vmx.c > +++ b/arch/x86/kvm/vmx.c > @@ -5672,22 +5672,20 @@ static int handle_pause(struct kvm_vcpu *vcpu) > return 1; > } > > -static int handle_nop(struct kvm_vcpu *vcpu) > +static int handle_invalid_op(struct kvm_vcpu *vcpu) > { > - skip_emulated_instruction(vcpu); > + kvm_queue_exception(vcpu, UD_VECTOR); > return 1; > } > > static int handle_mwait(struct kvm_vcpu *vcpu) > { > - printk_once(KERN_WARNING "kvm: MWAIT instruction emulated as NOP!\n"); > - return handle_nop(vcpu); > + return handle_invalid_op(vcpu); > } > > static int handle_monitor(struct kvm_vcpu *vcpu) > { > - printk_once(KERN_WARNING "kvm: MONITOR instruction emulated as NOP!\n"); > - return handle_nop(vcpu); > + return handle_invalid_op(vcpu); > } > > /* -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/