Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752819AbdLMLpa (ORCPT ); Wed, 13 Dec 2017 06:45:30 -0500 Received: from mx1.redhat.com ([209.132.183.28]:59758 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752778AbdLMLpY (ORCPT ); Wed, 13 Dec 2017 06:45:24 -0500 Subject: Re: [PATCH v8 1/4] KVM: X86: Add vCPU running/preempted state To: Wanpeng Li Cc: "linux-kernel@vger.kernel.org" , kvm , Paolo Bonzini , =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , Peter Zijlstra , Wanpeng Li References: <1513128784-5924-1-git-send-email-wanpeng.li@hotmail.com> <1513128784-5924-2-git-send-email-wanpeng.li@hotmail.com> <3fb56993-3bb6-442c-f12e-0c99c06ef5c2@redhat.com> From: David Hildenbrand Organization: Red Hat GmbH Message-ID: <692741fa-ff8b-add6-36f2-87374ff9abaa@redhat.com> Date: Wed, 13 Dec 2017 12:45:21 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.27]); Wed, 13 Dec 2017 11:45:24 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1682 Lines: 49 On 13.12.2017 12:38, Wanpeng Li wrote: > 2017-12-13 18:20 GMT+08:00 David Hildenbrand : >> On 13.12.2017 02:33, Wanpeng Li wrote: >>> From: Wanpeng Li >>> >>> This patch reuses the preempted field in kvm_steal_time, and will export >>> the vcpu running/pre-empted information to the guest from host. This will >>> enable guest to intelligently send ipi to running vcpus and set flag for >>> pre-empted vcpus. This will prevent waiting for vcpus that are not running. >>> >>> Cc: Paolo Bonzini >>> Cc: Radim Krčmář >>> Cc: Peter Zijlstra >>> Signed-off-by: Wanpeng Li >>> --- >>> arch/x86/include/uapi/asm/kvm_para.h | 3 +++ >>> arch/x86/kernel/kvm.c | 2 +- >>> arch/x86/kvm/x86.c | 4 ++-- >>> 3 files changed, 6 insertions(+), 3 deletions(-) >>> >>> diff --git a/arch/x86/include/uapi/asm/kvm_para.h b/arch/x86/include/uapi/asm/kvm_para.h >>> index 09cc064..763b692 100644 >>> --- a/arch/x86/include/uapi/asm/kvm_para.h >>> +++ b/arch/x86/include/uapi/asm/kvm_para.h >>> @@ -51,6 +51,9 @@ struct kvm_steal_time { >>> __u32 pad[11]; >>> }; >>> >>> +#define KVM_VCPU_NOT_PREEMPTED (0 << 0) >>> +#define KVM_VCPU_PREEMPTED (1 << 0) >> >> Is it really helpful to have two flags? >> >> Just use KVM_VCPU_PREEMPTED and clear that one in record_steal_time() > > I think it is fine since there is a third flag introduced in patch > 2/4, it is more clear currently. > > Regards, > Wanpeng Li > Having two flags representing the same thing is not clear to me. -- Thanks, David / dhildenb