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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B2354C433F5 for ; Tue, 2 Nov 2021 16:37:11 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 5F12060E9C for ; Tue, 2 Nov 2021 16:37:11 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 5F12060E9C Authentication-Results: mail.kernel.org; dmarc=fail (p=quarantine dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=lists.xenproject.org Received: from list by lists.xenproject.org with outflank-mailman.220427.381704 (Exim 4.92) (envelope-from ) id 1mhwmD-0003rQ-IS; Tue, 02 Nov 2021 16:36:45 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 220427.381704; Tue, 02 Nov 2021 16:36:45 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1mhwmD-0003rJ-Ef; Tue, 02 Nov 2021 16:36:45 +0000 Received: by outflank-mailman (input) for mailman id 220427; Tue, 02 Nov 2021 16:36:43 +0000 Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1mhwmB-0003qx-Kz for xen-devel@lists.xenproject.org; Tue, 02 Nov 2021 16:36:43 +0000 Received: from de-smtp-delivery-102.mimecast.com (unknown [194.104.109.102]) by us1-rack-iad1.inumbo.com (Halon) with ESMTPS id d15fe036-757a-4759-b38c-5db01a67c164; Tue, 02 Nov 2021 16:36:42 +0000 (UTC) Received: from EUR03-DB5-obe.outbound.protection.outlook.com (mail-db5eur03lp2052.outbound.protection.outlook.com [104.47.10.52]) (Using TLS) by relay.mimecast.com with ESMTP id de-mta-3-fpMJvkbQNa2-BMI1ujX0Ew-1; Tue, 02 Nov 2021 17:36:40 +0100 Received: from VI1PR04MB5600.eurprd04.prod.outlook.com (2603:10a6:803:e7::16) by VE1PR04MB6382.eurprd04.prod.outlook.com (2603:10a6:803:122::31) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4649.17; Tue, 2 Nov 2021 16:36:38 +0000 Received: from VI1PR04MB5600.eurprd04.prod.outlook.com ([fe80::8062:d7cb:ca45:1898]) by VI1PR04MB5600.eurprd04.prod.outlook.com ([fe80::8062:d7cb:ca45:1898%3]) with mapi id 15.20.4649.020; Tue, 2 Nov 2021 16:36:38 +0000 Received: from [10.156.60.236] (37.24.206.209) by AM5PR04CA0017.eurprd04.prod.outlook.com (2603:10a6:206:1::30) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4649.15 via Frontend Transport; Tue, 2 Nov 2021 16:36:37 +0000 X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: d15fe036-757a-4759-b38c-5db01a67c164 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=mimecast20200619; t=1635871001; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=gXdttXKkhlq2EKKHB51M9XelpFL4mhE9EhXefEQ5kdM=; b=J6pyRG4WNUAtrqNNIQSq5dfnYrlLZZaRsmO2fPNbZ0rM9JNMQTvwV53glchZlcJoG7g/Py 3uVfDv9CYtL4m6rDWZ9/hpxdae+hN5PG8dSY+Xqiv/qT+VgcQnvzYZOnxMj/GzKr6zG6qH ZrjRJV4bmE8FGLLxjmydeeH330+OmXo= X-MC-Unique: fpMJvkbQNa2-BMI1ujX0Ew-1 ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=akGZbqHy0o0BP9L/w+hJ/CRklaspvbbn4JvKA3EX0ZDdoIKZaqI9rg59jpbgQDcd4Rh9JLUfHN2/wxeK9Dfz2ggHXe7JVV3O6hPnKYtDv8IZeSFRM3+dU83mq6MkMKm4amxK5+8Mp94SBudvuduTm2mG6CRISqfFAgib70KALrDFlh9OPESVI0OyptxC96spboPPUeE/oQ25tCMKHbRy9rJq5McIKL6sbGxGscuXKTlSiWwhAvBSvjyv2hlq/dwyCRphz0x0ucsixm4B0lFKcmU2zXZDOddz/RbU+xK3YQKvXapkhqB5moROpqH9OEwuOLkzqugoYmTnKpvZL2rS4Q== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector9901; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1; bh=gXdttXKkhlq2EKKHB51M9XelpFL4mhE9EhXefEQ5kdM=; b=DEoh9tQRm+SucEeNVU5NWmsBmH653ULWAc2C+bnGNS/6ERnh9FjAYD8FLqhj9Gi6TXtbf8HljYMheDKwMOyRclWN1KuWP+xGid7tWPoexoZ4bkQ94vNDPb4nIbZays+FwAMloRSBuHfH0TUUPu5YmLvb8t7HKmqdBUrVv4AtNvR8m53WWW0uRAIumD56ky8eKsuYvg2yFmKs2nHdiQVr6ZT3wz8g2qIypUYLRKdKn9wdv4avfMCmTC6gsO+9bdCrGOrK6Rr+D+znMUM+uxAqjUtF9TVUo9YH5Ybu/d5ZLhajSEkzmrqReRk+MuAjG8MZHb3+hj9IN+hbVdX6aQP3Hw== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=suse.com; dmarc=pass action=none header.from=suse.com; dkim=pass header.d=suse.com; arc=none Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=suse.com; Message-ID: Date: Tue, 2 Nov 2021 17:36:36 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.2.1 Subject: Re: [PATCH v2 1/1] xen: update system time immediately when VCPUOP_register_vcpu_info Content-Language: en-US To: Ian Jackson Cc: Dongli Zhang , sstabellini@kernel.org, julien@xen.org, Volodymyr_Babchuk@epam.com, andrew.cooper3@citrix.com, george.dunlap@citrix.com, wl@xen.org, joe.jin@oracle.com, xen-devel@lists.xenproject.org References: <20211025173523.3647-1-dongli.zhang@oracle.com> <24961.24756.236341.888900@mariner.uk.xensource.com> From: Jan Beulich In-Reply-To: <24961.24756.236341.888900@mariner.uk.xensource.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-ClientProxiedBy: AM5PR04CA0017.eurprd04.prod.outlook.com (2603:10a6:206:1::30) To VI1PR04MB5600.eurprd04.prod.outlook.com (2603:10a6:803:e7::16) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 8e02431e-dd4c-4385-e974-08d99e1ef134 X-MS-TrafficTypeDiagnostic: VE1PR04MB6382: X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:9508; X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:VI1PR04MB5600.eurprd04.prod.outlook.com;PTR:;CAT:NONE;SFS:(366004)(31686004)(15650500001)(26005)(508600001)(4326008)(316002)(16576012)(53546011)(186003)(956004)(2906002)(2616005)(31696002)(6486002)(7416002)(36756003)(83380400001)(6916009)(66946007)(8676002)(66556008)(5660300002)(86362001)(966005)(38100700002)(8936002)(66476007)(14773001)(45980500001)(43740500002);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?cC9McHg2aXdrbDBiWEZSZ3hvbFVLdnc5eVhmc2o1MDl2Qlh2TmxjVU9xNFh1?= =?utf-8?B?ZXIvN2cvYkFaN1BlcDBNL1dUd3lwRXRhb3d6a1BxQ09Kd2Q2aTcrTkUrUElR?= =?utf-8?B?MnVLVml0ZXUrdFRKNHpuN251Wkk5aCtxdDBsVWFzOWsrb0lvdkZFMWk5WEFV?= =?utf-8?B?RVl1d09NOHVmQ1hzUzdkSTgxNU5EWDJnMkRXUnY2aTFrN3hiUmNaMmRjUWhC?= =?utf-8?B?dmsvSzRHdCtTc2FZdUlxcUlpbThjWkhIOWRXd05lMmZGWHdaS0V0L094VTEy?= =?utf-8?B?eUR1UjAxVStzRDM4Nys3Q0JnTFBPOERTWWxXSHNRWkx1eU8zK0V6NnM2dk1P?= =?utf-8?B?UDcrOW95VWxNbFlIZlBUSHpEYUg2c1owRFVTTjJ2SGc1bksvb1dWVElLU0VQ?= =?utf-8?B?Y2E5LzBGY1JjVUxHYzNwMlQrZDJWS3cxaHNTTXBSMUU4L0lhSkhWbkZ3Vmho?= =?utf-8?B?dERzdjJrWlEwRWlXay95VW1OMytrNmE3WXBDSVlwWGxoMEZKY2c2WmRhTFhy?= =?utf-8?B?MU0yQXRGUG40Ymp1TmVLWjZWc3VpY0kwbldjaFU4WDZNMnIwa0FvUDdqZEhG?= =?utf-8?B?a3prT0VLSWtLcmREeUlIUXI4ZEppMjA5TlpRZTA4UlRKMmJJUXZEcFBweklE?= =?utf-8?B?SENCdUJVUlRWY3dVRjI0b3hCRmdhc3AzbElXZGNNWDVLajMybWY4ekE4S0I2?= =?utf-8?B?M015QzdKVHM5Ym9wekkvcmJzdWRiYmpablVVbXdNMVV1OFhlVDRxOFZQZVJK?= =?utf-8?B?L3ltRHVOd0JXNjlQcmxOaWthL3ZEYlZaL0o0cUV0cTBBcHd1eURSMXpkZDlN?= =?utf-8?B?dXN5QXdkV2sxMUhGWkFDemZLOFh3QldyM2VTdVp5UHhTM2Zod1Noa0tlaXl5?= =?utf-8?B?VUw5Rkh2NGtnK3AzSWhCMGhQZjRFMDQ0b3hJU3VYZDV6UVVreGQzV0hFWUkx?= =?utf-8?B?NWU4Nk55OExIS2pKdVJ0dkhnSFU4eDBEc0l5cGkxYVpWeGYrZTg1eXlRQmtl?= =?utf-8?B?bDVMdWtyWDk4U2R4NTlzREhFVzIrd2VyOVk1aklTVVRJVUpMV0RFQi9heUVU?= =?utf-8?B?VGd4VTRrMXBHNlRWQnE2cDVoRWhpa21xSDg1Ri96VUtBa0Z5a0gzeHZkb2hr?= =?utf-8?B?VVJ4anVtc3g2YnNIWkd0NzJpdU01Zmd0Z3AwOUhucWllcjBFN3JrQTNqbEx1?= =?utf-8?B?VjkxSzRjWDE0NGw5RlJaNUhzY3RxdSt1Rld1RHV6eDd0K1hkWHdqS2dWQ2Uy?= =?utf-8?B?SXkxQ1BTMzBhS3BtL2pkYm9OUEtZckNxZ1VTSTdJbkMwTkprRnlRcWJuQ2Ni?= =?utf-8?B?dVJ2bGFHYzI3akJtYVdwa29SNW9OVmtXd2F3RldwYkI3UzdIMXVLUWNIY01Y?= =?utf-8?B?VG5EZmtqTkc0REJsTG1VcW14MGFtNnJyS0RaN1U3aGE5VUFsZFE0a2ZLakwz?= =?utf-8?B?ZkhHRWdQUG45eGRiYmhUNFQrVnk3dGN6SzlnT3NMNVBWNlhaRHpObTBEdmxE?= =?utf-8?B?N0xUT1ViWVFMQlg0Z0NSVGUwczFGTWZQSTR1ZTkvNkxDZDBWd0ZWN1ZOQ3ZS?= =?utf-8?B?NVJDdStvOER4cjBZaVBDZDMxdTZhWVJHbmprQ1RRemFTR0c4eGNwMmtCdUZZ?= =?utf-8?B?TGNPRFVIajEzVWpqL1hBeUJYc2Qrb0FsWUJlQUlJQWNOSTdHU3hIWlVFemZr?= =?utf-8?B?aFI1VEM0OU80bnBIVkJiWWVRT3pOa1JYbm5udGxpakhPcS8xNHk2MTRpcEgv?= =?utf-8?B?cTIwY0ZseG5kVVV3c0JMY0FVc2dkVXRySkc5K2FvUmlTWmJxZ0Z4ZkRkWFox?= =?utf-8?B?ZFJwNi8vdXhjQit4TkNNcHE0VVo3eDRvY051Skp6WTRDTHYzL09vZU4yRWtr?= =?utf-8?B?dDN1bFllRGErTmV3MzkvY1lMVlVxR1VmWHhOYk5HVzNxRVhHTkx4RjR2TWU4?= =?utf-8?B?N0taNitiNHF3cTFBZW9xY3lQNXVOZU5rNzVnUy9uVDgwcTZLeDBaWmw1VEI3?= =?utf-8?B?TEJtcnRGTHFsenZtUnhmWWd2WlcyWlVqcEh4dmVwNHBFbktNTnk2U0k0Mmln?= =?utf-8?B?QTJyYUlEV3JzeG5hbGkvTnRIMHZFTEZEdnZtSm1wTjlsK2Zxd2l0RjRwZ2tS?= =?utf-8?B?NlJQUUZ1ejhnRVJzWEpoYmR0VkpyY0Z3YUVHMXNkVmRCRThDZkNkdXRsMjRE?= =?utf-8?Q?zJryssJ4vDFZChXSROeB4Wk=3D?= X-OriginatorOrg: suse.com X-MS-Exchange-CrossTenant-Network-Message-Id: 8e02431e-dd4c-4385-e974-08d99e1ef134 X-MS-Exchange-CrossTenant-AuthSource: VI1PR04MB5600.eurprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 02 Nov 2021 16:36:38.3969 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: f7a17af6-1c5c-4a36-aa8b-f5be247aa4ba X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: 40/MD7Sqr8OddPWItjblIokwu76u5dDwuG6K9dTDwAON/sCfX7EgqkdUOc5uBQ361nAsyL79uuOUedGccR60HA== X-MS-Exchange-Transport-CrossTenantHeadersStamped: VE1PR04MB6382 On 02.11.2021 17:00, Ian Jackson wrote: > Jan Beulich writes ("Re: [PATCH v2 1/1] xen: update system time immediately when VCPUOP_register_vcpu_info"): >> On 25.10.2021 19:35, Dongli Zhang wrote: >>> The guest may access the pv vcpu_time_info immediately after >>> VCPUOP_register_vcpu_info. This is to borrow the idea of >>> VCPUOP_register_vcpu_time_memory_area, where the >>> force_update_vcpu_system_time() is called immediately when the new memory >>> area is registered. >>> >>> Otherwise, we may observe clock drift at the VM side if the VM accesses >>> the clocksource immediately after VCPUOP_register_vcpu_info(). >>> >>> Reference: >>> https://lists.xenproject.org/archives/html/xen-devel/2021-10/msg00571.html >>> Cc: Joe Jin >>> Signed-off-by: Dongli Zhang >> >> Reviewed-by: Jan Beulich >> >> Ian - any thoughts towards 4.16 here either way? > > This looks like a bugfix to me, and the diff is certainly small. I am > positively inclined. I would like to know what the risks are. > Stefano says this does nothing on ARM so the risk would be to x86. > Can you advise ? I don't see any noteworthy risks - a call to a function gets added in a 2nd place; the function itself has been working fine for years, and it is fine to be used in this new context. Jan