From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH 2/3] KVM: VMX: Short circuit STI; HLT while an interrupt is pending Date: Wed, 16 Feb 2011 11:01:47 +0200 Message-ID: <4D5B927B.50903@redhat.com> References: <1297694537-9268-1-git-send-email-avi@redhat.com> <1297694537-9268-3-git-send-email-avi@redhat.com> <20110215203654.GA16010@amt.cnet> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: kvm@vger.kernel.org To: Marcelo Tosatti Return-path: Received: from mx1.redhat.com ([209.132.183.28]:18548 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755636Ab1BPJBu (ORCPT ); Wed, 16 Feb 2011 04:01:50 -0500 Received: from int-mx09.intmail.prod.int.phx2.redhat.com (int-mx09.intmail.prod.int.phx2.redhat.com [10.5.11.22]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id p1G91ofI013228 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Wed, 16 Feb 2011 04:01:50 -0500 In-Reply-To: <20110215203654.GA16010@amt.cnet> Sender: kvm-owner@vger.kernel.org List-ID: On 02/15/2011 10:36 PM, Marcelo Tosatti wrote: > On Mon, Feb 14, 2011 at 04:42:16PM +0200, Avi Kivity wrote: > > Short-circuit an STI; HLT sequence while an interrupt is pending: > > instead of halting, re-entering the guest, and exiting immediately > > on an interrupt window exit, go directly to the last step. > > > > Saves a vmexit on workloads where interrupts are received synchronously; > > an example is a disk backed by the host page cache where there is no > > latency (from the guest's point of view) between the request and fulfilment. > > > > Signed-off-by: Avi Kivity > > --- > > arch/x86/kvm/vmx.c | 9 +++++++++ > > 1 files changed, 9 insertions(+), 0 deletions(-) > > > > diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c > > index ee1cd1a..541da0e 100644 > > --- a/arch/x86/kvm/vmx.c > > +++ b/arch/x86/kvm/vmx.c > > @@ -3437,6 +3437,15 @@ static int handle_interrupt_window(struct kvm_vcpu *vcpu) > > static int handle_halt(struct kvm_vcpu *vcpu) > > { > > skip_emulated_instruction(vcpu); > > + /* > > + * Short-circuit an STI; HLT sequence while an interrupt is pending: > > + * instead of halting, re-entering the guest, and exiting immediately > > + * on an interrupt window exit, go directly to the last step. > > + */ > > + if ((to_vmx(vcpu)->cpu_based_vm_exec_control > > + & CPU_BASED_VIRTUAL_INTR_PENDING) > > + && (kvm_get_rflags(vcpu)& X86_EFLAGS_IF)) > > + return handle_interrupt_window(vcpu); > > return kvm_emulate_halt(vcpu); > > } > > Why does the normal vcpu entry path fails to inject the interrupt? Because after halt, > KVM_REQ_EVENT is not set? Yes. Also, we want to clear CPU_BASED_VIRTUAL_INTR_PENDING. -- error compiling committee.c: too many arguments to function