From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-11.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 607B7C433DF for ; Mon, 17 Aug 2020 09:49:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 47A4B206FA for ; Mon, 17 Aug 2020 09:49:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726858AbgHQJtS (ORCPT ); Mon, 17 Aug 2020 05:49:18 -0400 Received: from foss.arm.com ([217.140.110.172]:52262 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726089AbgHQJtP (ORCPT ); Mon, 17 Aug 2020 05:49:15 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id ECBB631B; Mon, 17 Aug 2020 02:49:14 -0700 (PDT) Received: from [192.168.1.179] (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 84E493F66B; Mon, 17 Aug 2020 02:49:13 -0700 (PDT) Subject: Re: [PATCH 2/3] KVM: uapi: Remove KVM_DEV_TYPE_ARM_PV_TIME in kvm_device_type To: zhukeqian , Marc Zyngier Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, Catalin Marinas , Will Deacon , James Morse , Suzuki K Poulose , wanghaibin.wang@huawei.com References: <20200817033729.10848-1-zhukeqian1@huawei.com> <20200817033729.10848-3-zhukeqian1@huawei.com> <4cd543a2-4d5b-882c-38d6-f5055512f0dc@huawei.com> From: Steven Price Message-ID: <72e34f84-5bea-8f69-6699-29e2970c80b4@arm.com> Date: Mon, 17 Aug 2020 10:49:12 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <4cd543a2-4d5b-882c-38d6-f5055512f0dc@huawei.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 17/08/2020 09:43, zhukeqian wrote: > Hi Marc, > > On 2020/8/17 15:39, Marc Zyngier wrote: >> On 2020-08-17 04:37, Keqian Zhu wrote: >>> ARM64 PV-time ST is configured by userspace through vCPU attribute, >>> and KVM_DEV_TYPE_ARM_PV_TIME is unused. >>> >>> Signed-off-by: Keqian Zhu >>> --- >>> include/uapi/linux/kvm.h | 2 -- >>> tools/include/uapi/linux/kvm.h | 2 -- >>> 2 files changed, 4 deletions(-) >>> >>> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h >>> index 4fdf303..9a6b97e 100644 >>> --- a/include/uapi/linux/kvm.h >>> +++ b/include/uapi/linux/kvm.h >>> @@ -1258,8 +1258,6 @@ enum kvm_device_type { >>> #define KVM_DEV_TYPE_ARM_VGIC_ITS KVM_DEV_TYPE_ARM_VGIC_ITS >>> KVM_DEV_TYPE_XIVE, >>> #define KVM_DEV_TYPE_XIVE KVM_DEV_TYPE_XIVE >>> - KVM_DEV_TYPE_ARM_PV_TIME, >>> -#define KVM_DEV_TYPE_ARM_PV_TIME KVM_DEV_TYPE_ARM_PV_TIME >>> KVM_DEV_TYPE_MAX, >>> }; >>> >>> diff --git a/tools/include/uapi/linux/kvm.h b/tools/include/uapi/linux/kvm.h >>> index 4fdf303..9a6b97e 100644 >>> --- a/tools/include/uapi/linux/kvm.h >>> +++ b/tools/include/uapi/linux/kvm.h >>> @@ -1258,8 +1258,6 @@ enum kvm_device_type { >>> #define KVM_DEV_TYPE_ARM_VGIC_ITS KVM_DEV_TYPE_ARM_VGIC_ITS >>> KVM_DEV_TYPE_XIVE, >>> #define KVM_DEV_TYPE_XIVE KVM_DEV_TYPE_XIVE >>> - KVM_DEV_TYPE_ARM_PV_TIME, >>> -#define KVM_DEV_TYPE_ARM_PV_TIME KVM_DEV_TYPE_ARM_PV_TIME >>> KVM_DEV_TYPE_MAX, >>> }; >> >> No. You can't drop anything from UAPI, used or not. Doing so will >> break the compilation of any userspace that, for any reason, references >> this value. We cannot reuse this value in the future either, as it would >> create a we wouldn't know which device to create. >> >> It is pretty unfortunate that PV time has turned into such a train wreck, >> but that's what we have now, and it has to stay. > Well, I see. It is a sad thing indeed. Sorry about that, this got refactored so many times I guess I lost track of what was actually needed and this hunk remained when it should have been removed. I would hope that I'm the only one who has any userspace code which uses this, but I guess we should still be cautious since this has been in several releases now. Steve