From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: [PATCH 2/3] KVM: VMX: Short circuit STI; HLT while an interrupt is pending Date: Mon, 14 Feb 2011 16:42:16 +0200 Message-ID: <1297694537-9268-3-git-send-email-avi@redhat.com> References: <1297694537-9268-1-git-send-email-avi@redhat.com> To: Marcelo Tosatti , kvm@vger.kernel.org Return-path: Received: from mx1.redhat.com ([209.132.183.28]:47225 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755458Ab1BNOmd (ORCPT ); Mon, 14 Feb 2011 09:42:33 -0500 Received: from int-mx10.intmail.prod.int.phx2.redhat.com (int-mx10.intmail.prod.int.phx2.redhat.com [10.5.11.23]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id p1EEgXX4007480 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Mon, 14 Feb 2011 09:42:33 -0500 Received: from cleopatra.tlv.redhat.com (cleopatra.tlv.redhat.com [10.35.255.11]) by int-mx10.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id p1EEgWhP002951 for ; Mon, 14 Feb 2011 09:42:33 -0500 In-Reply-To: <1297694537-9268-1-git-send-email-avi@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: 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); } -- 1.7.1