From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.9]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C23C634FAF9; Tue, 6 May 2025 00:56:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=fail smtp.client-ip=198.175.65.9 ARC-Seal:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746492969; cv=fail; b=DWGZa6RpnRwyFqiBdcIlvHwYWMRXPNNB/I9Rgpwx3LLJfvbLJOUpn419YgHhEH8Rxz42MzRdupWhLmdSZUupdaeE0/Ek8BYuPNJf1ffnozIO/Wv/AK7u8QN+UJ75HH5NukSSddikRsGiqYhB3X/cVhK3ZKeWUylNMBZ9Xg6jBnE= ARC-Message-Signature:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746492969; c=relaxed/simple; bh=F4lh1V/V5d2qRgDWrdM6Deu3bL0waEiMC6wchGMnsjw=; h=Date:From:To:CC:Subject:Message-ID:References:Content-Type: Content-Disposition:In-Reply-To:MIME-Version; b=m1vD9DgE1rg3UfXdPp438nSMxr4LNRNObYFYpMjDYnZ1yPC/wG8HkRUPP3XobNnfuIdsFMOTcNg0wL6nXVGVh65NvoC4O0EwGwFVBsKX50MdyTiKeN3OgA2P2oCbMYSAaJiyEMoVzfCHxn7+pxESRfbU9LxLvR9xroOH5V3MU3A= ARC-Authentication-Results:i=2; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com; spf=pass smtp.mailfrom=intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=TLclY1HE; arc=fail smtp.client-ip=198.175.65.9 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="TLclY1HE" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1746492967; x=1778028967; h=date:from:to:cc:subject:message-id:reply-to:references: content-transfer-encoding:in-reply-to:mime-version; bh=F4lh1V/V5d2qRgDWrdM6Deu3bL0waEiMC6wchGMnsjw=; b=TLclY1HE7iy6g5HQTGDH1oE46w8QiHHR75KNtgKE77z3ZHjNxHzr2ZoQ gkBghO4JpD0IxUCc5TkMCw7Q+HL9Vqmz2QKyoqbRKIheviaxxGlFsPFAQ AY/7MQhRg4J+wE2Nz35s9tU+687xJaZNs3l+i/azTiD//P6aexl3H1bif ihxlUWTPPagGgWckKp9jj1J/w3qosww8fqfrinTL3J3GiSfmU3VJqAZJI XiiGyI6dPiAC5DWOnZPCFmape1mpVCNKn1woTm3HjL42GhEOt0W8hmcfA YSIU9ZkxP6/Yc5jqo+ZF0hbqiMJ78QLnoSDciSr/1236/uyi0QSePWEy1 w==; X-CSE-ConnectionGUID: iKOnc1O3SZ2oDmcflxmn3A== X-CSE-MsgGUID: Txolb+eeQ9Sx8mtoIUzoDA== X-IronPort-AV: E=McAfee;i="6700,10204,11424"; a="70634631" X-IronPort-AV: E=Sophos;i="6.15,265,1739865600"; d="scan'208";a="70634631" Received: from orviesa005.jf.intel.com ([10.64.159.145]) by orvoesa101.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 05 May 2025 17:56:05 -0700 X-CSE-ConnectionGUID: FdhSwTJERbOK7LManzvR/g== X-CSE-MsgGUID: 7Gi0+tErShWH1jPIBgMRHg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.15,265,1739865600"; d="scan'208";a="140572616" Received: from orsmsx902.amr.corp.intel.com ([10.22.229.24]) by orviesa005.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 05 May 2025 17:56:04 -0700 Received: from ORSMSX901.amr.corp.intel.com (10.22.229.23) by ORSMSX902.amr.corp.intel.com (10.22.229.24) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.14; Mon, 5 May 2025 17:56:04 -0700 Received: from orsedg603.ED.cps.intel.com (10.7.248.4) by ORSMSX901.amr.corp.intel.com (10.22.229.23) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.14 via Frontend Transport; Mon, 5 May 2025 17:56:04 -0700 Received: from NAM12-BN8-obe.outbound.protection.outlook.com (104.47.55.174) by edgegateway.intel.com (134.134.137.100) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.1.2507.44; Mon, 5 May 2025 17:56:01 -0700 ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=WqjPnmiMzwHL1ChHo0TCo71R2Xua5S/8ptWkoNowtEkqFm3XPk5UgmRJiK7Bc0RAq7ctc+q5LnHvN2kYFT7ZsC0UeBB6NZETbMATCX4ltonEZBKNXIhePpnHMDnOQtOcvambW/Ot9+13AzecfqS8Iho7RxCOORVpJTkBM2LIwW1X2PCWshrTnRsjOM3BocuTsIwUPouBomBUKw3HZnm9yCo+jQ6qYHhFsRIg4i1CyRIWm1bvOzWaAW/GYc2tKX7FPs4KNBIOMW9GWqDbH6d7YZcPqyFLQAFD3BO778tVU2Bv9gcOcbo3D3AAsvT8beOCwJDSECOz/DXgSxKAUz4xLQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector10001; 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=PL/mLh1wYn20dP457bAMZS/lqRNbR9lFyFk1WeOj/aM=; b=GNmXjjjqTs3OJyLs80KPrSmbQTPCJwIYxpST3rE112shFrepZRKCzOi886aFXErP0NjUiSmBRyMVtjIF5lvHp9F2StUmrOIOSRrODQkiM7iwQsUIi2gvLP6A7NinLZbpDIqO36PEE5e9wA9FK58cEyt/Ro0imOokW8pJHnr68H8lKyEwe4eCp3WbpLJnoOnbBkNUK+Se8kiL/YjqCEninPnNieU3E5xIarJcAQmk/9fmdEFM3+2PnyRE6yybh0evAFGQLJ7fuLaclr/rspYnrHobbJOqnijEqeIGYCYOvjxdychVLi40Tb0cOE/Zy1oQQjByg/i/FMjECUPUx3oeJg== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=intel.com; dmarc=pass action=none header.from=intel.com; dkim=pass header.d=intel.com; arc=none Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=intel.com; Received: from DS7PR11MB5966.namprd11.prod.outlook.com (2603:10b6:8:71::6) by PH0PR11MB4790.namprd11.prod.outlook.com (2603:10b6:510:40::17) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.8699.26; Tue, 6 May 2025 00:55:28 +0000 Received: from DS7PR11MB5966.namprd11.prod.outlook.com ([fe80::e971:d8f4:66c4:12ca]) by DS7PR11MB5966.namprd11.prod.outlook.com ([fe80::e971:d8f4:66c4:12ca%6]) with mapi id 15.20.8699.024; Tue, 6 May 2025 00:55:27 +0000 Date: Tue, 6 May 2025 08:53:26 +0800 From: Yan Zhao To: Vishal Annapurve CC: , , , , , , , , , , , , , , , , , , , , , , , , Subject: Re: [RFC PATCH 08/21] KVM: TDX: Increase/decrease folio ref for huge pages Message-ID: Reply-To: Yan Zhao References: <20250424030033.32635-1-yan.y.zhao@intel.com> <20250424030603.329-1-yan.y.zhao@intel.com> Content-Type: text/plain; charset="utf-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-ClientProxiedBy: OSAPR01CA0312.jpnprd01.prod.outlook.com (2603:1096:604:2c::36) To DS7PR11MB5966.namprd11.prod.outlook.com (2603:10b6:8:71::6) Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DS7PR11MB5966:EE_|PH0PR11MB4790:EE_ X-MS-Office365-Filtering-Correlation-Id: 7d35056e-e12b-46f6-889e-08dd8c38b140 X-LD-Processed: 46c98d88-e344-4ed4-8496-4ed7712e255d,ExtAddr X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|1800799024|7416014|376014; X-Microsoft-Antispam-Message-Info: =?utf-8?B?cktCd3J0Y2VJVytqY0VDMkxvZlltTmtBMG42NmhPWXY1djFhN0FpaWlYbmRN?= =?utf-8?B?Vi9TbEp3ek0yUjVJMVZDWE42YVR0SWRBaU5GMEpYMHRCVTBXUnErUmh0ZU1N?= =?utf-8?B?ZW9mZmI5djJ3SjhSaTNxbEYrWVB6d2pTT25pdW1MclBXTnZoNVQ5TkZ0QWdU?= =?utf-8?B?bk5XUEp4M1NvTnJaYnNoNjRxWEdRSTFvU0NwQnJzNGgwYzhEZlNrUy9qZE5P?= =?utf-8?B?M0FxcFNpOWlXM2UyY1Z5MUVqdjYxUXpvN1M4clI4QlQwaldiRk11Q3RxdmpN?= =?utf-8?B?THJ0RDhVKzhBWHVINS82azIrL2Nlcld2RDk0TnNWK1o4NHkwb3I5NldtR25s?= =?utf-8?B?UEVHcjc3dVNWbjgrOGJjSE1aMHc4ekJGZDlEcWpUeUZBTEczaHlOaXY0amt3?= =?utf-8?B?N01oaTg5cWlJbVNRYXN4TDZZQ1VBSHgzaDFxTnRMbEQ5UHYyOFErNnEvSDBj?= =?utf-8?B?cjFTVE10N28waUkwMm9qSFZBNk4yeFVRdTFEcTVlSFFQUHJyTnU2TnEyL2Fp?= =?utf-8?B?QU5EdHYwWHR3NEJoQWt0YzB2eE9TckxyTC8yelJ3Sm5IaTRjQ0owb09uUGhr?= =?utf-8?B?RVE4b0RSeEw3eitSVFczeEZRakRDTjYyRWZUMFAzZ3ZINFZxNkR3TUVUUjJr?= =?utf-8?B?S2VQeTNRTy9xQVpMaFJidkZiS0lFMUx1cXBBSEdkY3R1a2w5MkdCQmdKY2Zx?= =?utf-8?B?RHRxeFRkRHRBeGRNMmNwOU5uWFpXQXdhMHB5WDFtaERLL0hWK2dGelVNL1dT?= =?utf-8?B?VmRWcXRFZGxWRFN0Q1RqcjQzRlBnbXJBT0hqVUEvLzUxTXNrRFZLbkNYMWlq?= =?utf-8?B?YXk5Vi9rZHpRZU1nVHphTU94TkhuQXpyQjlBWFZFdXhIVzNMTlg1R09Lbktt?= =?utf-8?B?OElVRDNDZWFmWVdvRHJqSm5jZEhqKzhUQnJRNGNjcXpoY0ZJTkJVQW56OFg2?= =?utf-8?B?elBpUm5mbU5wK1JJc2t4QkFpQ0IwWkhnY0Z6U0pwNko3WUw3MWV0UkdpYllR?= =?utf-8?B?VWtwb1gxM2lKWmc5Z01tSGRnMW0yS1pQdzdScWdIcVN1czZmdzFLVEVIc1hm?= =?utf-8?B?VFBaMHo3MzFNeCs5OTNoaFFkUldXc2wvVXRld3VRTDJPODZoWnZ3amYvUTF3?= =?utf-8?B?R01zM2xvNVBwZ05yZExIbXIvaFMzR3BXSkg1M0hLUTk5UjNUOWpwampUaVR5?= =?utf-8?B?dGxBYWxMSU42ZmlTREJyK1BxU01SWEM0V2dRTjBaRDNRUEZYMkFXZ1Bpenlm?= =?utf-8?B?ejdjN0NjZ2pBSkZML0dmaWNiRG10TUF1QjloeG1iQVFkcXBOZjdpUWxxVzZo?= =?utf-8?B?S2dHQlF4WlYwRG90L2FJa1hxUC9kNkFjZlQrN1RCZFZNcTVJdEpBTHRheUU0?= =?utf-8?B?czRONmV3aWc0dUJSMTBGNmltcnJETWkwN1R4NFJUcEJOcTFFU0c4VFM1K0Zx?= =?utf-8?B?Q082eFRFTGYwNncxMG9XenlybHRWMC9JQ21iOW5GRmFFOXkzeDl3d2E3c3lW?= =?utf-8?B?UExXcytCcitHdjRqUThCWHpybStQM1dzbFQ2a0U1MzcwMHRQbTJyajlBVDNY?= =?utf-8?B?UWoxd1V1TEF1YXgzaHBGanVQWUpITGd1V0dTNWRKVWdDQ0hUTVNxUGlBK0di?= =?utf-8?B?TDRtSS9nakEvalJrNVB5WlAvOXRRNVdHZnkxL3MzczFhck1FWnBYQWoraGFL?= =?utf-8?B?Rm1FQVBwS3RzWmxIWXV3cnBrV2dQQWxIZVowWVZOcmdyWHdIdnUzaSt3VkNn?= =?utf-8?B?ZVRiSk9ZTGJISTIyUTJvRUd5UFR6a0laMTNrYVA5L2RQTmVzS2crOC8rYjNu?= =?utf-8?B?bzZ6Y1l5dnUwcmhYd0VMWlQ1aDFzYTJod1hTOTlIbllBODcrZk9Gcm1SNUpw?= =?utf-8?B?aHovT2g0cC8xMTl2UmxIcnY2bFU3UDU0ajc5cE0xdzRyekNOUXhHVWhpK25D?= =?utf-8?Q?HsLkZ9dcXHc=3D?= X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:DS7PR11MB5966.namprd11.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230040)(366016)(1800799024)(7416014)(376014);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?dTBVYkx1MUR0c2JmRGc5bkFlZytBU1F0NW1BbHVWbE5GVmgrSm9xV2NqS2Jp?= =?utf-8?B?Z2g3WUN5aUR5d29Jb29Pb0NRM0FrQk1HYXNna0gxSlNwcEcybkM1aXRJTUpM?= =?utf-8?B?QTAxNXBRc296bVA4aHJubFRBSmZzSXFyK3hBcTBPN3FaQ0pxbVR4dVNZNFlx?= =?utf-8?B?VGxnOFpJdDZLVlZvRmFWQ3ZPVDRURFkxWGxGVFVlMzJOdy9VRkJXc1NQK0RS?= =?utf-8?B?QmpYcGF5QmNsbmFEeFRIR2xuUHZTMFhFNzRCTGNoMmNyd2t3OHpYam9UOXJR?= =?utf-8?B?VmFodTA1MUluSDNNRGllWWFoSS9KbTI2UC9FWHdmZUVzKzNOVjRnaVJSWFR1?= =?utf-8?B?MTFTY0YxSkJSWmlQa0dZc0U2VlViUVJyT0hQcDJ1SEE3RzBGOG5ucnFCYi8w?= =?utf-8?B?bStyZE83cHZBcU0zdTFqeUMrbGlqWWkvTUczNWhaRk9Xb01ZNEF4YzJHa1Rn?= =?utf-8?B?MVFLL2puSEF6clc4SURUUEFhSjJUeEpuVnl4eGNhQ0J1UzZZZjBoZkVaeW1p?= =?utf-8?B?YVpxR01xelRJZ3dNWVlxZlFpZW0wVlRVYVlYK1ZkZGlwY0pJQWV3WlBhQTNO?= =?utf-8?B?S3ZIOVorU01TYnZQbFg4UG1mZW1HYWhOT01URHRDb1RGNFpVNTF5VkhhWnZV?= =?utf-8?B?MHhNbFdXYUNtdU1YTFdsZ2kzaG1tcDhSTkZqNHJEV01zYUF3cCswWitva0py?= =?utf-8?B?L1VGRHRRVHN6Yk1mQkpFaCs0clZYVkZUNUhUcHpvV0dra2t4WEVpWi9jT1Na?= =?utf-8?B?UUxRdzczeXZ1T01HUHdBNkg0eVRKUjhTeHZ1M1VEQlVrQ3NiY0REZ0VKUkRE?= =?utf-8?B?MTg2UklGS3hIMVEwc3BPbTNSa3BHMkc3Um5NcTlVSmw2bVREY0lldnJuQjNI?= =?utf-8?B?UjhjT1ZIUlM3RDVmQVFpVldlY3NXS1hmL2NyTW04NitKMVY3dmdzRGdZcnZU?= =?utf-8?B?VU13Z1Q2Nk53cWhYVXlaUHRjMHNSTG1uWnRPTWQzV0FucWtBbVZsb2dJWTQv?= =?utf-8?B?Q3lWdk1ySXU0K2hXdEhpdmtWd293NVB2NUJGdEVwZzVlSU9Zb0tpNStWdUFZ?= =?utf-8?B?QnFuN1pxL3lzUUhSYVk1dWJiM1dwTTA4clE1blMwcm10WmloemJpeFZRS3Y4?= =?utf-8?B?WjJEdGRJRncyNmRzaHlKY05lVzNkYTZpWk5JT1hwcWM5NlZReDloamx3OHJi?= =?utf-8?B?Zy93U1VRUllEYU92QjczSkRUY1IyaHRPYkdrMXROKy9VM2YyazZRSlltZHNh?= =?utf-8?B?a0JnY1F1VW5EUjlFOGIxb2EvN2tIQ1VyanFvWUpaY3FlK1hoUWtUaEI0Rmpm?= =?utf-8?B?T1FiZmpEdDdFZVFPN1pMeDNFeDFVVjJZZXlhQ1pIVVI4UWpUeDBMcURlNHRl?= =?utf-8?B?emNpRmV5c0JwcXRPOXVkT0EyQk15Y01RU3F2aG9KR0dwTkI5SXJwSzRWNnA0?= =?utf-8?B?NzV4d05oZlZWVE1LTThlMGNtbjBWdkpBeXQ4aTJhd01wRVVBWmI2dWk0ZWRp?= =?utf-8?B?K3MrSVU0c09aa293YjJZQ1pqbUxpbmVnS2QyZ0Z3WnFFeWJLUWZPV2VxVG5y?= =?utf-8?B?Y21mUFdLUmtZTnlsbHc2aG1KSVdjRElIVGk5V21wK29FTmhBeGF4eUJhdWhn?= =?utf-8?B?Z1JwNzcwVnUrQVdaRVlvT1FVVHdaa0NndDkzeldmTExiU1ZhSVpLM1NjWmlF?= =?utf-8?B?TWdaVGJMRStRUWppbWl5bEpJVkxPU3J1andZNFhGVDhINlBZRFRyRmlHVVor?= =?utf-8?B?N0ZSNmg2Wjc1bzNzN0NpT3NVc3pINDRvRTMzdTQyUVJpRXU3aFBhLzFCNUw2?= =?utf-8?B?OU41QlhXaFdraDdvVTMvT3EvYTk1RTBNMVk1ZDdoN3I3S0s0blpGTFFzdjJs?= =?utf-8?B?U3U4UFN4eUovM082cnQySi9ZV2lYRVFyNlJrVHRhQmdoRldiZG15dy9vaU1x?= =?utf-8?B?S1F6MFYrYkRaRityc3hOWGIvbHFXL2Z2akk0YTNMWWY5VmdVY2VxMnlSMzN0?= =?utf-8?B?L0RPSkpoNk1oRzBKZU5rZUx6VDd0cWNLbXplSndlZFBLQVBVWGxuamptaFBu?= =?utf-8?B?ZjFKeFV3QnpSQzlKUCt1MmdVdnNTYkM1RHI2NHJ2T3VtallIQmNpc1d4VmMx?= =?utf-8?Q?xkAm80ADWo/Nh104p/mbNc8+O?= X-MS-Exchange-CrossTenant-Network-Message-Id: 7d35056e-e12b-46f6-889e-08dd8c38b140 X-MS-Exchange-CrossTenant-AuthSource: DS7PR11MB5966.namprd11.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 06 May 2025 00:55:27.8446 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 46c98d88-e344-4ed4-8496-4ed7712e255d X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: in4zEwRtd5lHokspYPm2C0Z2WY/d6UufiTDPMyNfiQTTzXHGRn6yg0Me35zTkWTRLum93SZmhCvMdkVkwubrOQ== X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH0PR11MB4790 X-OriginatorOrg: intel.com Sorry for the late reply, I was on leave last week. On Tue, Apr 29, 2025 at 06:46:59AM -0700, Vishal Annapurve wrote: > On Mon, Apr 28, 2025 at 5:52 PM Yan Zhao wrote: > > So, we plan to remove folio_ref_add()/folio_put_refs() in future, only invoking > > folio_ref_add() in the event of a removal failure. > > In my opinion, the above scheme can be deployed with this series > itself. guest_memfd will not take away memory from TDX VMs without an I initially intended to add a separate patch at the end of this series to implement invoking folio_ref_add() only upon a removal failure. However, I decided against it since it's not a must before guest_memfd supports in-place conversion. We can include it in the next version If you think it's better. > invalidation. folio_ref_add() will not work for memory not backed by > page structs, but that problem can be solved in future possibly by With current TDX code, all memory must be backed by a page struct. Both tdh_mem_page_add() and tdh_mem_page_aug() require a "struct page *" rather than a pfn. > notifying guest_memfd of certain ranges being in use even after > invalidation completes. A curious question: To support memory not backed by page structs in future, is there any counterpart to the page struct to hold ref count and map count?