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mx.microsoft.com 1; spf=pass smtp.mailfrom=citrix.com; dmarc=pass action=none header.from=citrix.com; dkim=pass header.d=citrix.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=citrix.onmicrosoft.com; s=selector2-citrix-onmicrosoft-com; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=Tr66IaaFKvdb6843PQjk0JRCDkL/c0JzHSQRIzV86/g=; b=C9Hb9Gbs9b5Wrj9GYshtKKuuWsD07Tm3SMSmtZyIZYgmvOKRAjtsxFTx6bPomZeJ/LTqU2diP3MH2SlZ+Cre9tgv+FkAA8p62ZOtUv2Wqdd67ja6+w8H5kdcrCE1vVbuyJnN+/vSmxCTnVphEd5EYEb3bm4F+LpuspqiKAuyQwM= To: Jan Beulich , "xen-devel@lists.xenproject.org" CC: Wei Liu , =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= , Juergen Gross , George Dunlap , Ian Jackson References: <0bebfe8c-6897-dc8b-7fe0-9127d4996eb8@suse.com> <668ef720-389f-4cf1-608e-64aca4f7c73d@suse.com> From: Andrew Cooper Subject: Re: [PATCH v2 03/13] libxenguest: deal with log-dirty op stats overflow Message-ID: Date: Mon, 5 Jul 2021 16:41:38 +0100 User-Agent: Mozilla/5.0 (X11; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?K01XeHBONEZ3bmtmaCtCUWV3YmN3Wmt5UHRBZm50Ym1VVXNBNHpHRTJNTGNh?= =?utf-8?B?WXZJU1FZSjBMcWxvQXRvdHlUS2dtVGFkNElCVjZsR1pUSVVEdklFVmZzbXJZ?= =?utf-8?B?UEJyUXc2Rzd5Skw0S2hQMDhtSFBVVjFsb3F2TjBxdUNKTlkrZTVKSnVNeENI?= =?utf-8?B?bi9KWEQ1Y0pSb1ZLVUJ5TUgwZEFmc2NhMk1IeWQvWERsZkxZNHo5aTRKZEtq?= =?utf-8?B?NHExV1FNa2hLTnlQbzkyTjg5QTJtT2s1bDRYaEo3WUNWUGUzdjQzYnlCaVpD?= =?utf-8?B?UjR0d0dSK1oyZlBDaFdwL3h5S1J2Z3FCTVlkLzRvZ2laMkZiTFkxaGE4WkF2?= =?utf-8?B?SklmdEljQ3FZZzNobUJma2hNbXkrZ3FUYVA0OERSakUxSWRzOU0vRDA4L0Z5?= =?utf-8?B?TnBYY29pU1VSVnAxVVhpZlZ3K0RNUUNMUFl3cjlOY0ZUQ2hIZll0bVVjcWRs?= =?utf-8?B?Z2k3Q3JScFZYYzV2WWtxbStTYndZQ1Zyd3UwenByRXpEV29VZ1RXMVc4ME5U?= =?utf-8?B?MzQ4YkNMSEpBcktRTUlIZGtVUDZoMEtwdVZSb214MTI5WUpJdTJkN0IxTTZt?= =?utf-8?B?aXNRSU5XMTBFTjJsUjUreUovRm5NUkgwM2ZJaysvOXdrUDJZeGJSWHUyM3Bo?= =?utf-8?B?SnhCR1VTek5IZDVOWlpqYWtVZ3hLOXROSXhTeXJYcm9LK3JqalRwLzUvQ04z?= =?utf-8?B?QVdLZ2JSZXR1eGZpbWhRRy9QbHJSbGlpeHZkUXQ4WlhaejNhdzBYVVNkblpx?= =?utf-8?B?TXVaaTdvTnlCTmZuUEZoVHpRS1AvK2IwUTR1RFBSZklHcGR3MVl5S2lUckJN?= =?utf-8?B?M0o4Mnl3TEtMbDFDVndTOFBBbCtOUmV5TnZKeWQ2ZCtMdGpiVkNUdUJ2S0hl?= =?utf-8?B?a1VvVWpjVkxxa05LMFdZWVNGQzRCeEJaRGQxZG1XQ2FOZXdkQm85d2t2dDEr?= =?utf-8?B?SzNLQ21lQWhNaEdya1ZBek5rNHhuY2lCZVNJV0pEM1FOTG5keG9GQ3Y2d3J6?= =?utf-8?B?QU82NUsrSThKVjhRcnM2T1RmQzB6VFQzb2o3UmhZYXdGWENoREd6ODR1NGkx?= =?utf-8?B?c01kTjFidUlSRkkwWTB6ZjJVemN5M1hRbVBybWZSeTZWSjQ5UU55MjJFdVg3?= =?utf-8?B?RFFZRm5HeHYzRGtEK1hVdDNlamdDc0J2L2lKQ1hhWUg1ZWhxL041OEltTTJI?= =?utf-8?B?MHJqYjdySWdMbEsva2tnc003cDZoWlJOUitXeGliRzhMTVJHclhRNFAzRmZS?= =?utf-8?B?TGw2Y2U5RTJiWGsxd0Q4QUZTV3kxYVBpU1RNMDl2T0FSL1V2T3RBdWQwajEy?= =?utf-8?B?MWQybHpLV0pYMDVrYmdUNUNYdFU3aEdqM0REMU1EdjJOZWlSNVJlTDVFL0p6?= =?utf-8?B?MW9SSzhra1BMUCtNOG9RZk1kQWlkbDNHZGJnWkxNaitDYTVuRmU3dk1jWHht?= =?utf-8?B?WTVmTWQvY2xsdStlNFdQcEpwNUhoOHVqSXVoaFkxREZwbm4vdjZzM0ltZ3VR?= =?utf-8?B?OHRGdkpIK2VWNjIra3A0V2haSFByN2dqUEZWemdrejQ3V1BNOE5icDg1WWY4?= =?utf-8?B?NDFGSkVJNEIvN1Y0aG0vVlBjM3BnLzFZTDJTMDlRbitKZ1V3UTl1a0FORVdH?= =?utf-8?B?UU1wWmRLOWw5dmUweHd5d1RBOGdUUnlsQUYzUFFIVGluM0FMb2ZrUFZhVVFr?= =?utf-8?B?a3hIdHNrWkV2NVlFOTlmQUF0RllDZ01aMEdtbnRzei9vWGJnZVhBY2wxaWVZ?= =?utf-8?Q?E0rDoUnuAcVBBtiF7EefFDjLLgt2QoBtCxS3zPA?= X-MS-Exchange-CrossTenant-Network-Message-Id: 421f6dee-3b72-45e9-9a2a-08d93fcb64c5 X-MS-Exchange-CrossTenant-AuthSource: BYAPR03MB3623.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 05 Jul 2021 15:41:45.4136 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 335836de-42ef-43a2-b145-348c2ee9ca5b X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: 1em0FHe2W8SB3SULJ7eABCyn1ptPRvTMEZ6AUdHso0y9Nr+ixgNQuAiPBP7QqLpgHHFma9OcPJvGrzbzLyDDVXXQ8+vmEm1JlPj1PTjlkQs= X-MS-Exchange-Transport-CrossTenantHeadersStamped: BY5PR03MB4999 X-OriginatorOrg: citrix.com On 05/07/2021 16:13, Jan Beulich wrote: > In send_memory_live() the precise value the dirty_count struct field > gets initialized to doesn't matter much (apart from the triggering of > the log message in send_dirty_pages(), see below), but it is important > that it not be zero on the first iteration (or else send_dirty_pages() > won't get called at all). Saturate the initializer value at the maximum > value the field can hold. I've already explained why this is broken... > While there also initialize struct precopy_stats' respective field to a > more sane value: We don't really know how many dirty pages there are at > that point. > > In suspend_and_send_dirty() and verify_frames() the local variables > don't need initializing at all, as they're only an output from the > hypercall which gets invoked first thing. > > In send_checkpoint_dirty_pfn_list() the local variable can be dropped > altogether: It's optional to xc_logdirty_control() and not used anywhere > else. ... and why this is broken particularly in the context of a later change, and ... > > Note that in case the clipping actually takes effect, the "Bitmap > contained more entries than expected..." log message will trigger. This > being just an informational message, I don't think this is overly > concerning. ... why this isn't ok. Why do I bother wasting my time reviewing patches in the first place. ~Andrew